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Methods and systems for controlling a state of a neurostimulator

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1. state as soon as the time t 510 is exceeded The state of the neurostimulator which is forced to be a desig nated state at time t 510 is indicated graphically by bar 522 In this example as long as the timet 510 is exceeded it does not matter when the implant thereafter stops detecting the magnetic field e g a magnet 220 being manipulated by the patient or caregiver the implant will be in the designated state if the magnetic field remains in place for longer than tenaz 510 longer than the time t orceog SLAC or shorter than the time t orceog 514C but at least as long as the time tenaz 510 0087 While embodiments may be configured so that the default behavior of the neurostimulator 106 during the time period 509 when the neurostimulator 106 is to be susceptible of toggling from whichever state it was in just before the US 2014 0094876 AI magnetic field was detected to a different state if the magnetic fieldis no longer detected by the magnet sensor 130 1 e if the magnet 220 is taken away there may be circumstances under which it is not desirable to allow a magnetic field to enable the neurostimulator 106 to deliver therapy Thus in some embodiments the neurostimulator 106 may be pro vided with a parameter or parameters programmable by a physician using a programmer 120 which will have the effect of disabling the state changing behavior of the neurostimula tor 106 based on the presence
2. of the electrodes 118 The electrode interface 200 may also encompass charge balancing and other functions required for a proper interface with neurological tissue The communication subsystem 208 allows the implanted neurostimulator 106 to communicate with the outside world For example the communication subsystem 208 is provided with a magnet sensor 130 and a magnet tracking subsystem 216 so that the neurostimulator 106 can recognize and adjust its behavior based on the presence or absence of a magnetic field from a magnet applied externally of the implant see e g FIG 2 0056 The communication subsystem 208 via the central processing unit 210 or otherwise may cause the memory subsystem 216 to record and store one or more data items relative to the magnet sensor 130 and magnet tracking sub system 216 such parameters the values of which correspond to the number of times the magnet sensor 130 detected the presence of a magnetic field or the times the neurostimulator 106 changed its state based on the presence of the magnet and into which state the neurostimulator 106 transitioned or the times the neurostimulator 106 was forced into one state or the other Similarly the neurostimulator 106 may be configured so that the memory subsystem 216 records and stores param eters the values of which correspond to some other action the presence of the magnet caused the neurostimulator 106 to take based on the presence of the magnet such as
3. state to a therapy enabled state or from a therapy enabled state to a therapy disabled state would re enter the MAGNET_TRACKING_IDLE software object state and would cancel the timer related to the magnet force off interval 508 On the other hand if this timer expires while still in MAGNET_FORCE_OFF_INTERVAL the magnet track ing software object would set the neurostimulator state to a therapy disabled state and would enter a fourth software object state labeled MAGNET_HAS_BEEN_FORCED_ OFF The magnet tracking software object would remain in this state until a magnetic field becomes no longer detected at which point it would return to the MAGNET_TRACKING_ IDLE software object state 0119 Embodiments of methods and systems for control ling the state of a neurostimulator based on the presence or absence of a magnetic field such as provided by an external magnet provided to the patient thus have been described While the present technology has been described in particular examples it should be appreciated that the embodiments should not be construed as limited by such examples but rather construed according to the claims 0120 Various example embodiments are thus described All statements herein reciting principles aspects and embodiments of the present technology as well as specific examples thereof are intended to encompass both structural and functional equivalents thereof Additionally it is intended tha
4. an implanted neurostimula tor relative to the presence of an external magnetic field such as provided by a magnet 220 FIG 2 will now be described In sum the timing diagram reflects what neurostimulator 106 does after it begins to detect a magnetic field and then it either ceases to detect the magnetic field or a certain time interval is exceeded 0073 In FIG 5 the neurostimulator 106 may detect the presence of a magnetic field e g because the patient is holding a magnet next to the implant site so that the presence of the magnetic field is detected by a magnet sensor 130 in the neurostimulator 106 for a first interval referred to as a mag net toggle interval 504 and for a second interval referred to as a magnet force off interval 508 0074 In an example ifthe patient holds a magnet in prox imity to the implanted neurostimulator 106 for a time longer than the magnet toggle interval 504 and at least as long as the magnet force off interval 508 the neurostimulator 106 will disable therapy regardless of whether therapy was enabled or disabled just before this particular application of the magnet Apr 3 2014 0075 On the other hand if the patient holds a magnet next to the neurostimulator 106 longer than the magnet toggle interval but for a time that is less than the end of the magnet force off interval i e the time period 509 in FIG 5 the neurostimulator 106 will toggle the state of therapy as soo
5. block diagram illustrating an active implantable medical device in its use environment implanted in a patient 0004 FIG 2 is a schematic illustration of a patient manipulating an external magnet relative to the site at which an active implantable medical device has been implanted in accordance with an embodiment 0005 FIG 3 is a schematic illustration of the position of an external magnet after the manipulation indicated in FIG 2 has occurred 0006 FIG 4 is a block diagram of an implantable respon sive neurostimulation system which may be used with embodiments 0007 FIG S is a timing diagram illustrating a sequence of events in a method for selecting a state of an active implant able medical device that is configured to be in at least two states in accordance with embodiments 0008 FIG 6 is a timing diagram illustrating a feature of generating auditory feedback in a method for selecting a state of an active implantable medical device that is configured to be in at least two states in accordance with other embodi ments 0009 FIG 7isa flow chart of a method for selecting either a therapy disabled state or a therapy enabled state of an active implantable medical device according to embodi ments 0010 The drawings referred to in this description should not be understood as being drawn to scale unless specifically noted DESCRIPTION OF EMBODIMENTS 0011 Various embodiments are described below with
6. case the patient or patient s car egiver may be able to satisfactorily address the issue of turning the implant off e g disabling electrical stimulation therapy because of unpleasant side effects right away by using the magnet but if the patient wants to turn the implant back on he or she will have to wait until a doctor s visit or until the implant otherwise can be connected to a programmer or other external component other than the magnet to do so 0021 It can also be appreciated that an active implantable medical device configured to turn off when the presence of a magnet is detected for at least a certain period of time 1 the second case mentioned above in fact may turn off acciden tally when the patient is in the presence of a strong enough magnetic field even if the patient does not intend to turn the implant off Environmental magnetic fields that might be strong enough to affect a magnet sensor in an active implant able medical device might occur in an airport by proximity to airport security screening apparatuses or in a hospital by proximity to strong magnetic fields used in imaging or forms of treatment If the particular active implant is not delivering a type of therapy that the patient typically can feel for example a patient may not normally feel electrical stimula tion delivered to neural tissue then the patient may have no practical way of knowing for sure whether a recent trip through airport sec
7. example in the responsive neurostimula tion system under investigation by NeuroPace Inc under the trade name RNS SYSTEM the control module of the neu rostimulator interfaces with electrodes that are also implanted in the patient and which the neurostimulator can configure either as sensing elements or as stimulation elements 0052 In FIG 4 an electrode interface 200 of the control module 108 functions to select which electrodes of the elec trodes 118A 118B 118C and 118D hereinafter electrode 118 unless otherwise noted are used by the neurostimula tor 106 in which configurations and for which purposes e g sensing data from the patient or delivering therapy to the patient 0053 The control module 108 is provided with a self contained power supply 206 which may be a primary cell or rechargeable battery that supplies the voltages and currents necessary for each of the other subsystems of the neurostimu lator 106 to carry out its intended function s and a clock supply 212 which supplies needed clock and timing signals 0054 The control module 108 is provided with a memory subsystem 204 and a central processing unit CPU 210 which can take the form of a microcontroller 0055 The central processing unit 210 controls a therapy subsystem 214 which is configured to output a form of therapy e g electrical stimulation therapy to the patient for example via the electrode interface 200 and then one or more
8. field applied from an external source such as magnet that 15 supplied to the patient as part of the neurostimulation system 0028 The neurostimulator 106 is shown implanted in a patient 124 e g implanted in a ferrule which is situated during a craniotomy The neurostimulator 106 is configured to deliver a form of therapy to the patient that is intended to modulate the activity of the neural cells of the patient such as current controlled or voltage controlled electrical stimula tion therapy For example the neurostimulator 106 can be placed in operable communication with one or more elec trodes an oval shaped single electrode 118 is shown in FIG 1 Electrodes can be configured with the neurostimulator 106 in various stimulation pathways to deliver stimulation to the patient s tissue 0029 The neurostimulator 106 may be programmed to deliver stimulation to the patient continuously or on a peri odic or scheduled basis In some cases the neurostimulator 106 may only have the capability to deliver stimulation In other cases the neurostimulator 106 may have more complex capabilities For example a neurostimulator configured as a responsive neurostimulator may have the capacity to deliver a form of therapy when it detects a pattern of activity or other event in one or more channels of electrographic signals continuously monitored from the patient e g using leads bearing electrodes that are implanted in or on the brain
9. interval 508 after which the neurostimulator 106 becomes susceptible of toggling from the state it is in to a different state may for example cause one or more of the following to occur 1 causing the neurostimulator 106 to store in its memory a record corresponding to the electrical activity the neurostimulator 106 was sensing at some point during that magnet detection period 2 causing the neuro stimulator 106 to store in its memory one or more values corresponding to the date and a time when the magnet was detected e g a time during the magnet detection period corresponding to a particular magnet swipe and 3 caus ing the neurostimulator 106 to introduce some form of a marker into a record of electrographic activity being created in the neurostimulator 106 at some point during that magnet detection period e g a marker indicating that the patient swiped the magnet at a particular point during the recording of the neurostimulator 106 0093 FIG 6 is similar to the timing diagram of FIG 5 illustrating the behavior of a neurostimulator 106 relative to the use of a magnet when the magnet is applied at a time t start US 2014 0094876 AI 502 and then removed 1 before a time t 506 at endpoint of a magnet toggle interval 504 top panel 512A 2 after the time t 506 at the endpoint of a magnet toggle interval 504 but before a time t 510 at the endpoint of a magnet force off interval 508 middle pane
10. is or is not present relative to the neurostimu lator 106 The magnet sensor output may be binary 1 a signal that is either at one level or another or a bit that is either a 1 or a 0 The neurostimulator 106 may be configured so that a high magnet sensor output corresponds to the neuro stimulator 106 detecting the presence of the magnetic field and a low magnet sensor output corresponds to the neuro stimulator 106 not detecting the magnetic field The neuro stimulator 106 may include algorithms and or physical com ponents or circuits for conditioning the output of the magnet sensor 130 to improve it before it is used to affect the behavior of the neurostimulator 106 For example the neurostimulator 106 may debounce the output of the magnet sensor 130 before allowing a state change of the neurostimulator 106 based on the magnet sensor 130 output to occur 0051 The various functions of the neurostimulator 106 can be described with reference to a control module 108 that allows the implant to interface with elements for delivering a Apr 3 2014 therapy to the patient and with the outside world In the responsive neurostimulator 106 the control module 108 may also be configured to interface with elements for sensing physiological data such as electrographic signals from the patient In some responsive neurostimulators the same ele ments can be used for sensing physiological data and deliv ering therapy For
11. may be at too high of an amplitude or frequency or because the patient is going to sleep and the patient does not notice tremors while sleeping and therefore has no desire to receive the therapy during that time 0016 A neurostimulator that can be disabled by a mag netic field is also desirable in certain medical situations in which it is impractical or inefficient to communicate with the implanted device using telemetry with a programmer For instance in an emergent situation e g a patient comes into the emergency room and a caregiver tells emergency room personnel that he has an active implanted medical device and the ER wants to subject the patient to for example an imag ing procedure like an MRI being able to disable a function of the implant using a magnetic field from a readily available magnet may be a practical alternative to using a programmer to accomplish the same thing Thus a magnetic field may be used for some limited control over the active implant s behav ior whenever it is not practical or desirable to resort to other ways of communicating between the implant and the outside world that otherwise might be available e g near field or long range telemetry 0017 It will be appreciated that a patient may simply wish to suspend a particular therapy being delivered by an active implant for any of a variety of reasons until the patient can get US 2014 0094876 AI some feedback from a physician For example a
12. may not be whether his symptoms are getting worse despite the therapy delivered by the implant or whether his symptoms are recur ring because the implant is not delivering stimulation at all If the patient cannot tell which state the implant is in the patient may need to visit a doctor to sort it all out e g so that the physician can use a programmer to establish an inductive telemetry link to the implant and thereby turn it back on or re enable stimulation therapy as the case may be Thus implants configured in this toggling second mode may also be inconvenient especially if a particular patient is prone to over use of the magnet 0024 Thus it would be beneficial if the patient could be sure of what state an active implantable medical device is in e g or off stimulation enabled or stimulation disabled stimulation at full programmed strength or reduced stimulation etc when the patient uses the magnet in an effort to manipulate the implant It further would be beneficial if the patient did not have to keep a magnet up against the implant site in order to be confident that the active implantable medical device was either in one state or the other 0025 Associating the effect a magnet has on an implant with some sort of auditory or other somatosensory feedback may be helpful and in fact is a feature included in some of the embodiments described herein However incorporating this type of
13. niques well known in the art the ferrule in which the neuro stimulator 106 is positioned is not shown However it should US 2014 0094876 AI be appreciated that the placement described and illustrated herein is merely an example Other locations and configura tions are also possible depending on the size and shape of the device and the patient s needs among other factors 0037 Generally the neurostimulator 106 is positioned to follow the contours of a patient s cranium 102 However other locations within the patient body are also possible For example the neurostimulator 106 may be implanted pecto rally not shown with leads extending through the patient s neck and between the patient s cranium 102 and scalp 0038 With continued reference to FIG 1 the neurostimu lator 106 includes a housing 104 that encapsulates electronics that allow the desired neurological signals to be detected and or recorded and stored and the therapy e g electrical stimulation therapy to be delivered Other implantable com ponents of a neurostimulation system including the neuro stimulator 106 include electrode s 118 for monitoring or measuring electrographic signals and or for delivering elec trical stimulation to the patient s neural tissue An electrode 118 may be formed from a platinum member It will be appreciated that a neurostimulation system may include con figuring a neurostimulator 106 to be in operable communica tion
14. patient with an implanted neurostimulator may think he or she is experi encing some side effect associated with the therapy and therefore may want to stop delivery of the therapy until the patient can consult with a physician in a clinic visit or over the telephone 0018 Active implantable medical devices that are config ured to adjust their behavior based on the presence or absence of a magnet are known where 1 the implant is turned off when a magnet is present and only for so long as the magnet is present 1 implant s function is restored as soon as the implant no longer detects the magnet and 2 the implant is turned off when a magnet is present for a minimum period of time and then remains off until such time as a physician can turn it back on e g in an office visit 0019 In the first case the patient or the patient s car egiver is somewhat inconvenienced insofar as the external magnet has to be held next to the implant site unless and until the patient is amenable to having the device function restored if the patient or caregiver takes the magnet away the device will come back If the patient is not in a position to establish a telemetry link between the implant and the outside world e g with a physician s programmer right away then the patient will have to be vigilant about keeping the magnet next to the implant site until some other intervention can take place 0020 In the second
15. state a second different audible tone whenever the active implantable medical device is susceptible of transi tioning from the first medical device activity state to the second medical device activity state between the end of the first interval and the end of the second interval and whichever of the first or second audible tones that cor responds to the predetermined one of the first or sec ond medical device activity states if the sensor still detects the presence of the magnetic field after the second interval US 20140094876 1 as United States a2 Patent Application Publication Pub No US 2014 0094876 A1 Wingeier et al 43 Pub Date Apr 3 2014 54 71 72 73 21 22 METHODS AND SYSTEMS FOR CONTROLLING A STATE OF A NEUROSTIMULATOR Applicant Inventors Assignee Appl No Filed NEUROPACE INC Mountain View CA US Brett Wingeier San Francisco CA US Barbara Gibb Foster City CA US Craig Baysinger Livermore CA US Thomas Tcheng Pleasant Hill CA US Suresh Gurunathan Palo Alto CA US NeuroPace Inc Mountain View CA US 13 631 820 Sep 28 2012 Publication Classification 51 Int Cl AGIN 1 36 2006 01 52 1 5 no AGIN 1 36128 2013 01 USPC 607 62 57 ABSTRACT A method and system is described for ensuring a state of an active implantable medical device based on the presence and pe
16. subsystem 202 is coupled with both the central processing unit 210 and the memory subsystem 204 so that data representative of sensed EEG signals can be recorded and stored 0063 It should be noted that while the memory subsystem 204 is illustrated in FIG 4 as a separate functional subsystem the other subsystems might also use various amounts of memory to perform the functions described herein as well as other functions Further while the control module 108 may be a single physical unit contained within a single physical enclosure namely the housing 104 this does not need to be the case and the control module 108 may be configured dif ferently The control module 108 may be provided as an external unit not adapted for implantation or it may include a plurality of spatially separate units each performing a subset of the capabilities described above Also it should be noted that the various functions and capabilities of the subsystems of the neurostimulator 106 including the communications subsystem 208 and its magnet tracking system 216 may be Apr 3 2014 performed by electronic hardware e g hard wired modules computer software or firmware or a combination thereof The division of work between the central processing unit 210 and other functional subsystems may also vary The func tional distinctions illustrated in FIG 4 may not reflect the integration of functions in a real world system or method according to the embodime
17. the series of beeps 528 When the neurostimulator 106 ceases to detect the magnetic field at time t 514A the neurostimu lator 106 remains in the therapy enabled state and stops generating the beeps 528 0098 Referring now to the middle panel 512B of FIG 6 if the neurostimulator 106 continues to detect the presence of the magnetic field throughout the magnet toggle interval 504 1 until the time t 506 and if the neurostimulator 106 was a therapy enabled state at time t 502 then the beeps 528 will continue to be generated Then at the end of the magnet toggle interval 504 the neurostimulator 106 will become susceptible of toggling from the therapy enabled state to a therapy disabled state up until the end point of the magnet force off interval 508 1 up until the magnetic field is detected beyond the time t 510 In the example of FIG 6 the neurostimulator 106 stops detecting the magnetic field at the time t z 514B e g because the patient has taken a magnet 220 away from the location of the implant Through out the time the neurostimulator 106 is susceptible of toggling from the therapy enabled state to the therapy disabled state the long low tone 526 will be generated This will let the patient know that if the magnetic field is removed e g if the patient takes the magnet away then the neurostimulator 106 will toggle into the therapy disabled stat
18. the second endpoint and a third audible tone when the elapsed time is equal to the second endpoint the third audible tone being different from each of the first and second audible tones 13 The magnet tracking subsystem of claim 11 further comprising a first parameter a value of which corresponds to each time the presence of the magnetic field is recognized by the magnet sensor a second parameter a value of which corresponds to each time the elapsed time corresponds to a time within the interval and athird parameter a value of which corresponds to which of the first or second states the active implantable medical device is in each time the elapsed time corresponds to a time within the interval a fourth parameter a value of which corresponds to each time the elapsed time is greater than or equal to the second endpoint and amemory for storing the values of each of the first second third and fourth parameters 14 A method for controlling a state of an active implant able medical device having a tracking system for a magnetic field comprising monitoring an output of a magnetic field sensor maintaining the implantable medical device in a first state for so long as the presence of a magnetic field is detected by the magnetic field sensor until a first interval is sur passed if the first interval is surpassed determining whether a second interval has been surpassed Apr 3 2014 if the second interval has not b
19. time gt 510 the failure of the implant to continue to detect the magnetic field will cause the implant to transition from a first state to a second state e g from a therapy disabled state to a therapy enabled state or vice versa In other words if the active implantable medical device ceases to detect the magnetic field during the time period 509 and the implant was in the first state at the beginning at timet 502 then it will change to the second state at the 514B This transition from the first state to the second state is indicated graphically by line 520A and bar 520B On the other hand ifthe active implantable medical device ceases to detect the magnetic field during the time period 509 and the implant was in the second state when the magnetic field began to be detected at time 502 then the implant will transition to the first state at the time tr 514B This transition from the second state to the first state is indicated graphically by bar 518A and line 518B 0086 In the bottom panel 512C the active implantable medical device ceases to detect the presence of a magnetic field at a time t yoreog 514 Since the time toggie 514B occurs in the time period 509 after the magnet force off interval 508 has ended at the time t 510 then the active implantable medical device will be forced into a designated one of the first or second states e g forced into a therapy disabled
20. 14A When the magnetic field is no longer detected the neurostimulator 106 remains in the therapy disabled state and stops generating the long low tone 526 In another embodiment the long low tone 526 continues for a predetermined length of time or for a length of time determined by a programmed setting 0095 Referring now to the middle panel 512B of FIG 6 if the neurostimulator 106 continues to detect the presence of the magnetic field throughout the magnet toggle interval 504 1 until the time 506 then the long low tone 526 will continue to be generated Then at the end of the magnet toggle interval 504 the neurostimulator 106 will become susceptible of toggling from the therapy disabled state to a therapy enabled state up until the end point of the magnet force off interval 508 ie up until the magnetic field is detected beyond the time 1 510 In example of FIG 6 the neurostimulator 106 stops detecting the magnetic field at the time toggie 514B e g because the patient has taken a magnet 220 away from the location of the implant Through out the time the neurostimulator 106 is susceptible of toggling from the therapy disabled state to the therapy enabled state the beeps 528 will be generated This will let the patient know that if the magnetic field is removed e g if the patient takes the magnet away then the neurostimulator 106 will toggle into the therapy enabled s
21. 2222224 gt tend 506 509 504 a j tend2 510 tstarf 502 508 552 FIG 6 Patent Application Publication Apr 3 2014 Sheet 6 of 6 US 2014 0094876 A1 MONITOR MAGNET SENSOR 705 SENSOR INDICATES PRESENCE OF MAGNET 710 N NO MONITOR MAGNET SENSOR AND TIME INFORMATION 715 SENSOR INDICATES MAGNET REMOVED 720 HAS TOGGLE NO INTERVAL ENDED 735 HAS FORCE OFF INTERVAL ENDED 725 IS THERAPY DISABLE ENABLED THERAPY 740 145 ENABLE DISABLE THERAPY THERAPY 150 730 US 2014 0094876 AI METHODS AND SYSTEMS FOR CONTROLLING A STATE OF A NEUROSTIMULATOR FIELD 0001 The field relates generally to active implantable medical devices and more particularly to selecting a state of an active implantable medical device using an external com ponent such as magnet BACKGROUND 0002 Active implantable medical devices for example implantable medical devices that are configured to deliver energy or another form of treatment to the body such as for patients with epilepsy or a movement disorder often are configurable to communicate with an external component that includes a magnet The magnet may be used by the patient and or a patient s caregiver including a physician for some level of control of the active implantable medical devices BRIEF DESCRIPTION OF THE DRAWINGS 0003 FIG 1 is a
22. Ina responsive neurostimulator the same leads and electrodes that are used for delivering the therapy to the patient may also be used for monitoring electrographic signals from the patient 0030 Generally a responsive neurostimulator is config urable to sense signals from the patient corresponding to electrical activity of the brain to continuously monitor and process the sensed signal to identify patterns or other features of the signal or patterns and or features associated with the signal such as but not limited to the date or time the signal is sensed and or the condition of the implantable medical device at the time a pattern or other feature is detected e g whether a signal amplifier is saturated and if so for how long and to identify one or more events in the monitored signal when certain detection criteria are met e g meeting or exceeding fixed or dynamic thresholds trends A responsive neurostimulation system is under investigation by NeuroPace Inc under the tradename RNS SYSTEM US Pat No 6 016 449 to Fischell et al for System for Treatment of Neurological Disorders issued Jan 18 2000 and U S Pat No 6 810 285 to Pless et al for Seizure Sensing and Detec tion Using an Implantable Medical Device issued Oct 26 2004 also describing neurostimulation systems with respon sive capabilities U S Pat Nos 6 016 449 and 6 810 285 are incorporated by reference herein in the entir
23. Patent Application Publication Apr 3 2014 Sheet 1 of 6 US 2014 0094876 A1 Patient Remote Monitor Programmer 120A Programmer i 120B Patent Application Publication Apr 3 2014 Sheet 2 of 6 US 2014 0094876 A1 N N 220 222 S FIG 2 Patent Application Publication Apr 3 2014 Sheet 3 of 6 US 2014 0094876 A1 Neurostimulator 106 Control Module 108 Detection Subsystem Electrode 202 118A Memory Subsystem Electrode 204 118B Communication Electrode Subsystem Interface 208 Magnet Sensor 130 Magnet Tracking Subsystem 216 Electrode 118D Central Processing Unit 210 Therapy Subsystem 214 FIG 4 Patent Application Publication Apr 3 2014 Sheet 4 of 6 US 2014 0094876 A1 tstart 502 514A tswipe 5144 9 EUR UT 16 ttoggle 5148 A 520 520B i z I Ke U 518A aa z 5188 7 _tpostforceoff 514 oi 52099 mes tend 506 5097 504 tend2 510 tstart 502 1 508 se FIG 5 Patent Application Publication Apr 3 2014 Sheet 5 of 6 US 2014 0094876 A1 502 Ke tswipe 514A 2 EE 528 ttoggle 5148 526 EI 512B 528 I se mmm 526 sze tpostforceoff 514 512 Ea EI Es Es Es E EB El EE EE 576 5 2 LL HZ Z 526 10222
24. al 508 and persists for some predeter US 2014 0094876 AI mined time after the endpointt 510 when the magnet force off interval 508 has been exceeded and still another corre sponds to the time period 509 when the neurostimulator 106 is between the endpointt 506 of the magnet toggle interval 504 and the endpoint t 510 of the magnet force off interval 508 0101 The sounds s may be generated by the neurostimu lator 106 itself e g using an annunciator element and or circuit provided in the neurostimulator 106 Alternatively the tone s may be generated by some other component of a neurostimulation system based on commands received from the implant In other embodiments rather than being audi tory the feedback may manifest in some other somatosensory effect such as a vibration 0102 In still other embodiments when the feedback is auditory different tones may be used to indicate when the magnet has been recognized by the neurostimulator 106 when the neurostimulator 106 is in the time period 509 when it is susceptible of being toggled from a therapy disabled state to a therapy enabled state or vice versa as the case may be and when the neurostimulator 106 has been forced to a therapy disabled state i e after the endpoint of the mag net force off interval 508 at time t 510 has been reached or exceeded For example beeps generated at different frequen cies may be used for the different
25. as in just before the magnet was applied and the patient may not be certain what that prior state was Thus embodiments provide a method and system for using an external magnet to both select a state of a neu rostimulator that is configured to be in at least two states and ensure a state of a neurostimulator Example Method for Selecting a State of an Active Implantable Medical Device 0071 Embodiments provide a method for using an exter nal magnet to unequivocally change a state of an active implantable medical device In particular an example is described for a system and method for changing the state of a neurostimulator to disable and enable a therapy the neuro stimulator is configured to deliver to a patient e g electrical stimulation therapy In other embodiments and as noted above the behavior of the neurostimulator relative to use of the magnet may be to transition the neurostimulator between states other than therapy disabled and therapy enabled In still other embodiments the active implanted medical device need not necessarily be a neurostimulator Embodiments also provide an auditory feedback feature that can be relied upon together with the magnet to further enhance the patient s or the caregiver s degree of certainty with respect to the expe rience 1 as to whether the implant is in one state another 0072 Referring to FIGS 5 and 6 a sequence of events corresponding to the behavior of
26. auditory feedback signals The patient or caregiver may hear 1 a rapid series of beeps when the neurostimulator 106 is in the time period 509 1 when it is susceptible of toggling between the therapy enabled and therapy disabled states 2 a single short confirmatory beep when the neurostimulator 106 first detects the presence of the magnet at time t 502 in FIG 6 and 3 a longer confirmatory tone for a few seconds once the magnet force off interval 508 has been exceeded 1 after time 15 510 in FIG 6 and the neurostimulator 106 thus has been forced into a therapy disabled state In other embodiments a distinct tone may also be generated if the presence of the magnet ceases to be detected by the neurostimulator 106 while the neurostimulator 106 is in the time period 509 In other words if the neurostimulator 106 toggles states in the time period 509 a tone may be generated to confirm that such toggling occurred 0103 In still further embodiments the tones selected may correspond to which state the neurostimulator 106 is in for so long as the neurostimulator 106 detects the presence of the magnet and for some predetermined time after the magnetic field is removed For example one tone may be associated with a therapy enabled state and another with a therapy disabled state When the neurostimulator 106 has been forced into the therapy disabled state by leaving the magnet in place over
27. be delivered at the therapeutic level when the neurostimulator 106 is toggled into a therapy enabled state by removing the magnet during the time period 509 0112 Similarly embodiments are contemplated in which transitioning out of a therapy enabled state into a therapy disabled state is not a simple on to off action but rather the therapy is gradually decreased over some predetermined period of time until it is considered to be completely disabled Gradually ramping a therapy up or down when the neuro stimulator 106 transitions between states may be more appro priate in some applications of a neurostimulator 106 than in others For example ifthe patient is likely to sense the stimu lation while it is being delivered then titrating a parameter e g amplitude of the stimulation up or down during state changes may be desirable In other circumstances abrupt changes in therapy may have unwanted results relative to the symptoms the therapy is intended to alleviate e g the symp tom of tremor for a movement disorders application of a neurostimulator Apr 3 2014 0113 In some embodiments and as explained with refer ence to FIG 6 above the neurostimulator 106 causes one or more audible signals to be generated whenever the magnet is detected wherever the neurostimulator 106 is in the time period 509 1 e susceptible of toggling between states and whenever the magnet has been applied long enoug
28. by processors and electrical components under the control of computer readable and computer executable instructions The computer readable and computer executable instructions reside for example in a non transitory data storage medium such as computer usable volatile and non volatile memory However the computer readable and computer executable instructions may reside in any type of non transitory com puter readable storage medium 0115 It will also be appreciated that there are numerous possibilities for accomplishing the functions described above in a method and system according to embodiments For example the magnet tracking subsystem 216 see the block diagram of FIG 4 may be implemented as a magnet tracking software object capable of passing via an interface such as an event messaging buffer messages and information to other software objects such as software objects that control deliv ery of therapy The magnet tracking software object is con figured to exist in one ofa set of software object states where each software object state is characterized by one or more of the activity of the software object while in that software object state the events or conditions that cause a transition of the software object into a different software object state and the activities of the software object that occur when the software object transitions into a different software object state 0116 For example the magnet tracking software obje
29. ceeds both the first interval end point and the second interval end point forcing the state of the active implantable medical device to a first state regardless of the current state if the at least one time corresponding to removal of the magnet is determined comparing the at least one magnet removal time to the first interval end point and to the second interval end point and if the at least one magnet removal time is between the first interval end point and the second interval end point toggling the state of the active implantable medical device from the current state to either the first state or to a different state 2 The method of claim 1 wherein each of the states of the active implantable medical device corresponds to a level of activity of the active implantable medical device and the level of activity of the first state is different from the level of activity of any other state 3 The method of claim 1 wherein the first state is an inactive state 4 The method of claim 1 wherein toggling the state of the active implantable medical device further comprises when the current state is the first state toggling the current state to a second state and when the current state is the second state toggling the current state to the first state 5 The method of claim 1 further comprising generating a first alert at each start time and generating a different alert whenever the elapsed magnet detected time exceeds the fi
30. change modes or settings using various communication protocols While inductive telemetry is most commonly used for bidirectional communication with the implant e g to program a neurostimulator or to interro gate a neurostimulator to retrieve data from the implant an active implantable medical device also often is provided with a simpler unidirectional communication protocol that involves an external magnet manipulable by the patient or the patient s caregiver and a sensor in the implant configured to detect the presence or absence of the magnet 0014 Implantable neurostimulators are known that are provided with a magnet sensor such as a reed switch ora giant magneto resistive effect sensor GMR sensor The magnet sensor is configured so that when an external magnetic field e g from an external hand held magnet is brought near enough to the magnet sensor the neurostimulator will react to the presence of the magnet by disabling a therapy the neuro stimulator is configured to deliver 0015 For example if a patient has a movement disorder and has been implanted with a neurostimulator that is config ured to deliver electrical stimulation to the patient s brain as atherapy to reduce tremors a symptom of the patient s move ment disorder there may be times when the patient wants to disable the therapy for example because the patient experi ences some unpleasant sensation when the stimulation is delivered the stimulation
31. configured to respond to a condition when a magnetic field ceases to be detected within the first interval by toggling a medical device state from a first medical device activity state to a second different medical device activity state 18 The system ofclaim 17 wherein the first medical device activity state corresponds to a state in which a therapy the US 2014 0094876 AI Apr 3 2014 15 active implantable medical device is configured to deliver is disabled and the second medical device activity state corre sponds to a state in which a therapy the active implantable medical device is configured to deliver is enabled 19 The system of claim 17 wherein the active implantable medical device is configured to respond to the condition when the second interval has been exceeded by ensuring that the active implantable medical device is in a predetermined one ofthe first medical device activity state or the second medical device activity state unless and until the sensor ceases to detect the magnetic field and the magnet tracking software object is again in the first software object state and then the sensor begins to detect the magnetic field and the magnet tracking software object is again in the second software object state 20 The system of claim 17 further comprising a feedback signal generator the feedback signal generator configured to generate a first audible tone whenever the magnet tracking sub system is in the second object
32. ct could be configured to be in a software object state labeled MAGNET_TRACKING_IDLE when a magnetic field is not currently detected by the neurostimulator 106 Upon initial detection of a magnetic field the magnet tracking software object would enter a second software object state labeled MAGNET_TOGGLE_INTERVAL At this transition a timer implemented in software or hardware would be configured to run for the duration of the magnet toggle interval 504 US 2014 0094876 AI 0117 While in the MAGNET_TOGGLE_INTERVAL software object state the magnet tracking software object would respond to several conditions If a magnetic field becomes no longer detected then the magnet tracking soft ware object would re enter the MAGNET_TRACKING_ IDLE software object state and cancel the timer related to the magnet toggle interval 504 On the other hand if this timer expires while still in MAGNET_TOGGLE_INTERVAL the magnet tracking software object would enter a third software object state labeled MAGNET_FORCE_OFF_INTERVAL At this transition a timer implemented in software or hard ware would be configured to run for the duration of the magnet force off interval 508 0118 While in the MAGNET_FORCE_OFF_INTER VAL software object state the magnet tracking software object would respond to several conditions Ifa magnetic field becomes no longer detected then the magnet tracking soft ware object would toggle therapy e g from a therapy dis abled
33. d magnetic field to change the state of a neurostimulator 106 from a therapy disabled to a therapy disabled state by for example set ting the values for the magnet toggle interval 504 and the magnet force off interval 508 to 05 or by otherwise prevent ing the neurostimulator 106 from transitioning into a therapy enabled state whenever the magnet sensor 130 detects a magnetic field 0090 In other embodiments once an implantable neuro stimulator 106 has changed states from therapy disabled to therapy enabled or vice versa some maximum amount of times the implantable neurostimulator 106 may be controlled by a parameter that either disables additional state changes from therapy disabled to therapy enabled or only allows a transition into a state other than a therapy enabled state from a therapy disabled state For instance a physician may program a patient s neurostimulator 106 so that after a patient or caregiver has caused the implant to change from therapy enabled to therapy disabled five times in a single day further detection of the presence of a magnetic field will under no circumstances allow therapy to be enabled e g until the patient talks to his or her physician to confirm that the toggle behavior is desired and is not the undesired result of for instance strong environmental magnetic fields in the patient s workplace Alternatively after excessive toggl
34. e from the therapy enabled state 0099 Referring now to the bottom panel 512C of FIG 6 if the neurostimulator 106 continues to detect the presence of the magnetic field throughout all of the magnet toggle interval 504 and all of the magnet force off interval 508 1 from the time t za 502 through and including the time t 510 and if the neurostimulator 106 was in a therapy enabled state at time 502 then the beeps 528 will be generated for the entirety of the magnet toggle interval 504 from the time trar 502 to the time t 506 the long low tone 526 will be generated during the time period 509 between the magnet toggle interval endpoint time t 506 through the magnet force off interval endpoint time 1 510 and then the long low tone 526 will be generated again or just continue to be generated as soon as the magnetic field has been detected long enough to force the neurostimulator 106 into the therapy disabled state When the neurostimulator 106 ceases to detect the magnetic field at or after time t of 514C in FIG 6 neither the long low tone 526 nor the beeps 528 are generated 0100 Alternatively or additionally in some embodiments the magnet tracking system 216 may cause different sounds to be produced whenever the magnet sensor 130 detects the presence of a magnet where one sound corresponds to the magnet toggle interval 504 another corresponds to the mag net force off interv
35. een surpassed when the presence of the magnetic field is no longer detected transitioning the implantable medical device into a sec ond state and if the second interval has been surpassed ensuring that the implantable medical device is in a predetermined one of the first and second states 15 The method of claim 14 wherein a first audible tone is associated with the first state and a second audible signal is associated with the second state and the first and second audible tones are generated by the implantable medical devices as follows during the first interval if the implantable medical device is in the first state the first audible tone will be generated after the first interval but before the end of the second interval the second audible tone associated with the second state will be generated and after both the first interval and the second interval which ever of the first or second audible tones associated with the predetermined one of the first and second states will be generated 16 A system for controlling a state of an active implantable medical device having a tracking subsystem for a magnetic field comprising a sensor for detecting the presence of a magnetic field a magnet tracking subsystem including a magnet tracking software object configured to exist in one of a set of software object states each software object state char acterized by at least one of the activity of the software object while in each soft
36. ence of a certain magnetic field a timer configured to track a time period over which the magnet sensor continuously detects the magnetic field and to start tracking time when the presence of the mag netic field is detected and to stop tracking time when the presence of the magnetic field is no longer detected a comparator for comparing an elapsed time calculated by the timer and corresponding to the period over which the magnetic field is detected to a first endpoint and a second endpoint and if the elapsed time corresponds to a time within the interval between the first and second endpoints gen erating a comparator output that corresponds to a command to transition the active implantable medical device from a first state to a second state where the first state is different from the second state if the elapsed time is greater than or equal to the second endpoint generating an output that causes the active implantable medical device to transition to a prede termined one of either the first state or the second state 12 The magnet tracking subsystem of claim 11 further comprising an auditory feedback subsystem the auditory feedback subsystem coupled with the magnet tracking system and configured to generate a first audible tone when the timer starts tracking time a second audible tone that is different from the first audible tone when the elapsed time surpasses the first endpoint and for so long as the elapsed time is less than
37. er circumstances use of the magnet may cause the medical device to transition from a state corresponding to some level of activity to a state in which the device is completely off 0069 As will be discussed below embodiments enable a patient to change a state of a neurostimulator 106 determin istically or with certainty using a magnet A patient or car egiver can cause the neurostimulator 106 to go into a US 2014 0094876 AI therapy disabled state by holding the magnet over the implant for a long enough period oftime without having to be concerned about the state the neurostimulator 106 was in just before the magnet was applied Further once the patient or caregiver knows the neurostimulator 106 is in the therapy disabled state he or she can return the neurostimulator 106 to a therapy enabled state by following a simple procedure with the magnet 0070 These embodiments described here may be con trasted with other approaches to determining and or changing a state of a neurostimulator in which the patient is required to continuously hold the magnet over the implant in order to ensure therapy is disabled or in which a physician or other health care provider is required to assist with changing the state of the implant or in which the patient is left unsure after using a magnet as to exactly which state the implant is in e g because the result of applying the magnet depends on what state the neurostimulator w
38. erence to the top middle and bottom panels of FIG 5 where time is represented by the x axis 550 In each panel of FIG 5 the active implantable medical device begins to detect the presence of a magnetic field at the time t 502 In the top panel 512A the active implantable medical device ceases to detect the presence of a magnetic field at a time t 514A which occurs before the end point of the magnet toggle interval 504 at the time 506 As described above if the implant detects the magnet for less than the magnet toggle interval 504 the implant will not change state it will remain in whatever state it was in at the timet 502 A transient detection of a magnetic field by implant may cause nothing at all to happen However in some embodiments the presence of the magnetic field for less than the magnet toggle interval 504 may cause the implant to do something other than change states however as is described in more detail below in connection with the discussion of a magnet swipe The unchanged state of the active implant able medical device is indicated graphically by the bar 516 0085 In the middle panel 512B the active implantable medical device ceases to detect the presence of a magnetic field at a time t ogg e 514B Since the time t 514B occurs in the time period 509 after the magnet toggle interval 504 has ended at the time t 506 and before the magnet force off interval 508 has ended at the
39. ety 0031 The signals sensed from the patient may be moni tored by a physician or other caregiver in real time by con necting the implanted device to an external component such as a physician s programmer that is capable of communicat ing with the implant wirelessly such as via telemetry Alter natively or additionally the neurostimulator 106 may be con figured to store selected signals of the sensed signals according to certain programmed instructions Such storage may occur periodically whenever an event is detected or upon command from an external component such as a patient remote monitor 126 a physician s programmer 120A 120B 120C or 120D each of which may wirelessly communicate with the implant or a magnet see the magnet 220 in FIGS Apr 3 2014 2 and 3 the presence of which may be detected by a magnet sensor in the implant In an application of the responsive neurostimulator 106 to diagnose and or treat epilepsy for example the responsive neurostimulator 106 may be config ured to detect seizures and or seizure onsets or precursors 0032 The neurostimulator 106 records neurological sig nals such as electrographic signals in the form of electroen cephalographic EEG and electrocorticographic ECoG waveforms detects and analyzes electrographic signals and or creates a log of such an analysis In general EEG signals represent aggregate electrical potentials related to neuronal activity within the bra
40. functionality into a system that includes an active implantable device may be associated with costs or design trade offs that it otherwise might be desirable to avoid There fore embodiments described here include magnet behavior that allows the patient or a caregiver to unequivocally estab lish in which state an active implant is in with a simple procedure that can be set out in a patient user manual and or easily communicated to a patient from a help desk via telephone email or a website for example a website using a instant messaging utility OVERVIEW OF DISCUSSION 0026 The discussion begins with a description of an active implantable medical device the behavior of which may be controlled to some degree based on a signal generated by a magnet sensor provided in the implant More particularly the description is directed to a specific example of an implantable responsive neurostimulator configured with a magnet sensor and magnet tracking system that controls certain behavior of the neurostimulator in the presence of a magnetic field e g from an external magnet with which the patient is provided Active Implantable Medical Device with Tracking System for a Magnetic Field 0027 FIG 1 illustrates an active implantable medical device The device is a neurostimulator 106 configured with a magnet sensor 130 such that the behavior of the neurostimu US 2014 0094876 AI lator 106 may be affected by the presence of a magnetic
41. h to force the neurostimulator 106 into the therapy disabled state In still other embodiments whenever the magnet sensor 130 of the neurostimulator 106 detects the presence of the magnet the neurostimulator 106 will generate a signal such as an audible signal that allows the patient or caregiver to gauge whether the magnet 220 is close enough to the magnet sensor 130 For example a series of beeps at a certain tone may be configured to increase in frequency when the patient has the magnet 220 over a sweet spot relative to the magnet sensor 130 in the implanted neurostimulator 106 so that the patient can be assured that his or her use of the magnet will cause the behavior of the neurostimulator 106 the patient expects the magnet to cause 0114 It will be appreciated that there are numerous ways in which the method and system according to embodiments described above may be implemented For example soft ware hardware including ASICs FPGAs and other custom electronics and various combinations of software and hard ware are all solutions that would be possible to practitioners of ordinary skill in the art of electronics and systems design It should further be noted that the steps described herein as performed in software need not be as some of them can be implemented in hardware if desired to further reduce com putational load on the processor In various embodiments the methods and systems described above is implemented
42. he presence of the magnet continues to be detected and whether the magnet ceases to be detected 0108 Ifat block 720 the neurostimulator 106 still detects a magnet then at block 725 the neurostimulator 106 deter mines whether the magnet force off interval 508 has been exceeded If the magnet force off interval 508 has been exceeded then at block 730 the neurostimulator 106 is forced from a therapy enabled state into a therapy disabled state if the neurostimulator 106 was in a therapy enabled state when the presence of the magnet was first detected at block 710 or it is left in a therapy disabled state if it was in a therapy disabled state when the presence of the magnet was first detected at block 710 0109 If at block 720 neurostimulator 106 no longer detects a magnet then at block 735 the neurostimulator 106 determines whether the magnet toggle interval 504 has been exceeded If the magnet toggle interval 504 has been exceeded or has ended then at block 740 the neurostimu lator 106 determines which state the neurostimulator 106 is in Ifthe neurostimulator 106 is in a therapy enabled state at block 740 then at block 745 the neurostimulator 106 is transitioned or toggled to a therapy disabled state if the neurostimulator 106 is in a therapy disabled state at block 740 then at block 750 the neurostimulator 106 is transitioned or toggled to a therapy enabled state On
43. imulator 106 for a moment then reapplying the magnet so that the clock associated with time tsart 502 is reset and the magnet tracking subsystem 216 again begins to track what happens next in terms of how long the presence of the magnet continues to be detected and whether the magnet ceases to be detected The patient then can take the magnet away when the neurostimulator 106 is in the time period 509 when it is susceptible of toggling back to the therapy enabled state which will cause the neurostimulator 106 to transition into the therapy enabled state The patient or caregiver then can expect that the neurostimulator 106 will remain in the therapy enabled state unless and until the magnet sensor detects a magnet again Although in some circumstances the neurostimulator 106 may be configured to turn itself off under certain conditions that are not related to the presence or absence of a magnetic field 0111 In some embodiments the behavior of the neuro stimulator 106 after it has been forced into a therapy dis abled state may be more complex than in the example above A method and system according to embodiments may require that if the patient or caregiver wishes to transition the neu rostimulator 106 to a therapy enabled state once a magnet has caused it to be forced into a therapy disabled state the therapy will have to increase gradually up to a programmed therapeutic level rather than instantly
44. in detectable via sensors applied to a patient s scalp ECoG signals which are intracranial coun terparts to the EEG signals are detectable via sensors implanted over on or under the dura mater and often within the patient s brain Unless otherwise noted herein the term EEG shall be used generically herein to refer to both EEG and ECoG signals 0033 The neurostimulator 106 typically has a relatively large number and variety of parameters that can be set and subsequently be modified in a programming session after the neurostimulator 106 is implanted in a patient Thus for example the neurostimulator 106 may be programmed to begin recording detected EEG signals satisfying certain detection parameters or criteria e g based on a combination of parameter values from the patient 124 at the onset of ictal seizure activity or as a result of a prediction of ictal activity The neurostimulator 106 may be configured to record signals or values corresponding or related to signals at times before during and after the detection criteria have been met The neurostimulator 106 may continue recording until the ictal activity stops Optionally the neurostimulator 106 saves the recording or a sampling of it to a memory device to preserve it for later uploading to the external device 0034 Theneurostimulator 106 may also create a log of the ictal activity In one example the neurostimulator 106 records and or logs the date and time whe
45. ing between states e g more than 20 times when the neuro stimulator 106 next detects the presence of a magnetic field rather than toggling from a therapy disabled state to a therapy enabled state the neurostimulator 106 may change to a state in which some nominal level of therapy 1 e not the Apr 3 2014 full strength therapy corresponding to the therapy enabled state is delivered until a physician can be consulted about the situation In some embodiments the parameters that control whether the presence of a magnetic field will allow the neurostimulator 106 to changes states at all or that will condition state changes based on some other criteria may be programmed using a physician programmer or some other external component configured to communicate with the implant 0091 As described above an active implantable medical device according to embodiments may be configured to undertake action other than transitioning between one state to another upon detecting a magnetic field with its magnet sen sor 130 In some embodiments when a neurostimulator 106 detects the presence of a magnetic field beginning at timet 502 but for less than the end of the magnet toggle interval 504 1 before time 506 neurostimulator 106 will not change from a therapy disabled state to a therapy enabled state or vice versa but a magnet swipe before time t 506 may cause the neurosti
46. ipes the magnet over the implant the period of time the implant senses the magnet will be very short and this short presence of the magnet may cause the implant to undertake one of several possible actions Which actions the implant takes may be programmable by the physician or otherwise predetermined by a manufacturer s setting in the device Ina responsive neurostimulator that is configured to record elec trographic signals from a patient a magnet swipe may cause the neurostimulator to store a record corresponding to the electrographic signals being sensed by the device at the time of the magnet swipe or to place a marker in a record that the device is already storing at the time of the magnet swipe When the active implantable medical device detects the pres ence ofa magnetic field for longer periods of time then these longer periods of time may cause the implant to undertake different behaviors as are discussed in more detail below such as forcing the implant into one state or toggling the medical device from a state it was in just before the presence of the magnet was detected into a different state when the magnetic field is no longer detected e g when the magnet 220 is taken away 0050 FIG 4 is a block diagram of a responsive neuro stimulator 106 of FIG 1 as may be used for monitoring a signal generated by the magnet sensor 130 The magnet sen sor 130 is configured so that its output corresponds to whether a magnetic field
47. l 512B and 3 after the time t 510 at the endpoint of a magnet force off interval 508 bottom panel 512C However in FIG 6 the additional feature of auditory feedback is illustrated to con vey that in accordance with some embodiments the magnet tracking system 216 may be associated with one of two audi tory tones that are generated to guide the patient as to which state the neurostimulator 106 is in or to which state the neu rostimulator 106 will transition if the neurostimulator 106 ceases to detect the magnetic field i e which state the neu rostimulator 106 will go into ifthe magnet is removed More particularly in an example the therapy disabled state is associated with a long low tone which is represented by the shaded blocks 526 in FIG 6 The therapy enabled state is associated with a series of beeps which are represented by the strings of solid black rectangles 528 in FIG 6 In one embodi ment the auditory feedback is generated by a feedback signal generator such as a piezoelectric element driven by an oscil lator circuit or digital waveform generator 0094 Referring now to the top panel 512A of FIG 6 ifthe neurostimulator 106 detects the presence of a magnetic field at time tan 502 and neurostimulator 106 is then a therapy disabled state then the patient will hear the long low tone 526 In this example the neurostimulator 106 ceases to detect the magnetic field at time t 5
48. ld is removed the implant will transition into the second state 0083 In a typical case the magnet force off interval 508 will be considerably longer than the magnet toggle interval 504 For example a magnet force off interval 508 may be defined by values for relevant parameters as being twenty seconds long and a corresponding magnet toggle interval 504 may be defined by relevant parameters as being only five seconds long Thus when the magnet is held near the neuro stimulator 106 for a relatively long duration 1 longer than the magnet force off interval 508 the stimulation 15 disabled deterministically that is the stimulation is disabled whether or not it was enabled or disabled just prior to application of the magnet at the time t 502 Subsequently when the magnet is removed and then again held near the neurostimulator 106 for a shorter duration before it is again removed 1 for longer than magnet toggle interval 504 but for less than the whole of the magnet force off interval 508 or removed between the endpoint at the time t 506 but a time less than the endpoint at the time t gt 510 the stimulation is deter ministically enabled In other words after following this pro cedure the stimulation is enabled regardless of whether it enabled or disabled just before the two step procedure was undertaken Apr 3 2014 0084 method according to embodiments will now be described more particularly with ref
49. link 0045 More specifically a programmer 120 may selec tively connected with the network 122 such as the internet via a telemetry communication link This allows information that is uploaded from the neurostimulator 106 as well as program code or other information intended for download to the neurostimulator 106 to be stored in a database 128 at one or more data repository locations which may include various servers and network connected programmers This allows the patient s physician to have access to important data including past treatment information and software updates essentially anywhere in the world that there is a programmer e g programmer 120A or web browser not shown and a network connection 0046 A neurostimulator 106 according to embodiments has a magnet sensor 130 configured to detect a magnetic field For example such a magnet sensor 130 can be configured to detect the presence of a magnetic field when an external magnet is moved into the vicinity of the neurostimulator 106 by the patient 124 or a caregiver The neurostimulator 106 may be configured to modify its behavior when the presence of the magnet is detected by the magnet sensor 130 as is described in more detail below 0047 FIGS 2 illustrate a patient s use of an external magnet to modify the behavior of an implanted neurostimu lator 106 according to embodiments The patient brings a donut shaped magnet 220 next to a site 222 a
50. mulator 106 to take some other action For example the neurostimulator currently under investiga tion under the name RNS SYSTEM neurostimulator for NeuroPace Inc may monitor electrical activity sensed from the patient s brain and may record some of that activity in records that are stored at least temporarily ina memory in the neurostimulator The neurostimulator 106 may also record and store information about what the neurostimulator 106 is doing at a particular time during its operation e g the time and date a particular record of electrical activity was created and or stored an item of information corresponding to the remaining battery life of the implanted power source whether or not the device was capable of delivering neurostimulation to the patient at the level at which it was programmed to deliver the stimulation etc 0092 In situations in which the neurostimulator 106 has features similar to the aforementioned features for sensing electrical activity and or creating records and storing the records of the electrical activity and recording and storing device diagnostics type information corresponding to information about the behavior of the device itself as distin guishable from the electrical activity of the patient which the device is monitoring a magnet swipe in the period between the time t 502 and the time t 506 1 in which removal of the magnet occurs before the end of magnet toggle
51. n an event begins and ends the duration of the event indications of the intensity of the event etc The neurostimulator 106 optionally uploads such a log to an external device such as but not limited to a programmer 120A 120B 120C or 120D described in greater detail below The neurostimulator 106 may also be configured to record and or preserve data corresponding to EEG signals upon the initiation of some action e g swiping an external magnet near the site at which the neurostimulator 106 is implanted by the patient a caregiver or a physician 0035 In some embodiments the neurostimulator 106 detects and or predicts any kind of neurological event that has a representative electrographic signature While an embodi ment is described herein as responsive to epileptic seizures it should be recognized that the neurostimulator 106 can respond to other types of neurological disorders such as movement disorders e g Parkinson s disease migraine headaches chronic pain and neuropsychiatric disorders e g depression In various embodiments the neurostimulator 106 detects neurological events representing any or all of these afflictions when they are actually occurring in an onset stage and or as a predictive precursor before clinical symp toms begin 0036 Referring still to FIG 1 the neurostimulator 106 is shown as implanted in a space or volume formed in the patient s cranium by craniotomy or other neurosurgical tech
52. n as the neurostimulator 106 stops detecting the magnetic field that is the neurostimulator 106 will enable therapy if it was disabled just before this particular application of the magnet and will disable therapy if it was previously enabled just before this particular application of the magnet 0076 It will be appreciated that if the neurostimulator 106 first is forced into the therapy disabled state by reason of the fact that the neurostimulator 106 detected the presence of a magnetic field continuously throughout the end of the magnet force off interval e g by holding the magnet over the implant through and including the end of the magnet force off inter val then the patient or the patient s caregiver will be assured that therapy is disabled If the patient then wants to make sure therapy is enabled the patient can hold the magnet over the implant long enough to get past the magnet toggle interval and then remove it before the end of the magnet force off interval Now the patient will know the implant is in the therapy enabled state because when the magnet was removed during the time period in which the neurostimulator 106 was susceptible of toggling the neurostimulator 106 toggled from the therapy disabled state to the therapy enabled state 0077 Each of the magnet toggle interval 504 and the mag net force off interval 508 may be defined as parameters with parameter values in an algorithm for determini
53. ng a behavior of the neurostimulator 106 in response to the neurostimulator 106 detecting the presence of a magnetic field such as the behavior to disable therapy The neurostimulator 106 may implement this algorithm for example as part of the function of the magnet tracking subsystem indicated in the block diagram of FIG 4 0078 In this description the duration of each of the mag net toggle interval 504 and the magnet force off interval 508 are both measured or calculated from a common starting point namely 502 Alternatively the duration of each interval may be defined with reference to unique start and end times along the axis 550 corresponding to units of time for example the start time of the magnet force off interval may occur at the end time of the magnet toggle interval 0079 It should also be appreciated that embodiments pro vide a simple deterministic two step procedure to enable stimulation Put another way even if the patient is not sure which state the neurostimulator 106 is in when the process is started the patient will be sure which state the neurostimula tor 106 is in when the process ends namely in this example a therapy enabled state This deterministic two step proce dure is described as follows 1 applying the magnet for longer than the magnet force off interval 508 longer than the endpoint at the time t_ gt 510 in which case the neurostimu lator 106 will be transitioned in
54. nts disclosed herein 0064 Inone embodiment the neurostimulator 106 is pro vided with magnet sensor 130 such as a giant magnetoresis tance or GMR sensor that is configured to generate a signal that is a function of whether the magnet sensor 130 senses the presence of a magnetic field The signal generated by the magnet sensor 130 may be processed or conditioned using techniques well known in the art such as debouncing before it is used to control the behavior of the neurostimulator 0065 The patient is provided with a magnet for example the donut shaped magnet 220 shown in FIGS 2 and 3 which produces a magnetic field strong enough to be recognized by the magnet sensor 130 when the magnet 220 is brought into close enough proximity to the neurostimulator 106 Imple mentations of magnet sensors other than that using a GMR sensor will be apparent such as reed switches and the like 0066 A magnet tracking system 216 included in the neu rostimulator 106 is configured to initiate action based on whether the magnet sensor 130 generates a signal corre sponding to the presence of a magnet including actions that change the behavior of the neurostimulator 106 More par ticularly and according to one example the magnet tracking subsystem 216 may initiate action either 1 to disable the therapy subsystem 214 from delivering whatever therapy it might be programmed to deliver to the patient or 2 to toggle the state of the neurostimula
55. o perform the functions represented by the blocks in the block diagram of FIG 4 Most of the time the neuro stimulator 106 will function autonomously particularly when performing its usual sensing detection and recording capabilities but the neurostimulator 106 may selectively be put in communication with a programmer or a patient remote monitor to wirelessly transmit data from the neurostimulator 1 to interrogate neurostimulator and or monitor elec trographic signals from the patient in real time with an exter nal component or to transmit information to the neurostimu lator e g programming instructions updates to code the neurostimulator uses to carry out its functions etc 0042 To enable wireless interrogation and delivery ofnew programming instructions to the neurostimulator a telemetry antenna not shown may be provided inside or outside of the housing 104 The external devices may include devices com Apr 3 2014 monly referred to as programmers 120A 120B 120C and 120D which may be laptops or tablets or other computers with which a physician can interrogate the implant and change the programming of the implant and a patient remote monitor 126 with which the patient can interact in some limited fash ion with the implant such as to interrogate the implant so that data stored by the implant can be retrieved by the patient remote monitor and subsequently uploaded elsewhere for example over a netwo
56. or absence of a magnetic field In other words a physician may want to turn a patient s therapy off and not allow the patient to turn it back on using the magnet 0088 This may be the case where the patient is participat ing in a sham or placebo arm of a clinical trial in which therapy is temporarily turned off and in which iftherapy were to be enabled the scientific data derived from the patient would be compromised Similarly if the neurostimulator 106 is has the capacity to sense and record and store electro graphic signals from the patient as well as to deliver a form of electrical stimulation therapy to the patient e g a responsive neurostimulator the physician may wish to leave the sens ing recording and storing functions in operation but to dis able the stimulation until such time as the physician is able to diagnose what is happening with the patient and then use the diagnosis to decide upon a course of stimulation therapy In this case the physician may want the patient to still be able to use a magnet 220 for magnet swipes to cause the neuro stimulator 106 to record electrographic signals or to mark records of electrographic signals discussed further below but the physician may not want the patient to be able to use the magnet to transition the neurostimulator 106 into a therapy enabled state 0089 An implantable neurostimulator 106 may be pro grammed to block the ability for a detecte
57. r state e g the therapy enabled state 0081 Thus for example the features of some embodi ments that allow a magnet to be used to make sure a neuro stimulator s therapy is disabled may be relied upon not only by patients and their regular caregivers but also in emergent situations For instance emergency room personnel familiar with the neurostimulator s behavior relative to a magnetic field may be able to use a magnet to disable a patient s therapy while the ER personnel are trying to diagnose or treat the patient 0082 Instill other embodiments one or both of the values that determine the length of the magnet toggle interval 504 and the magnet force off interval 508 may be programmable by a physician and thus tailored for specific patients A phy sician may select values for each of the intervals by interact ing with the patient s implant using a programmer such as a programmer 120A anda wireless communications link to the implant When the values are programmable the values of course will have to be communicated in an appropriate man ner to the patient and or the patient s caregivers so that the patient will know how long the implant has to detect the presence of the magnetic field for the implant to be forced into a first state and then for how long the implant has to detect the presence of the magnetic field for the implant to be suscep tible of toggling into a second state so that when the magnetic fie
58. ref erence to detailed illustrative embodiments in the context of active implantable medical devices and in particular an implantable neurostimulator It will be apparent that the methods and systems described herein can be embodied in a wide variety of forms Consequently the specific structural and functional details disclosed herein are representative and do not limit the scope of embodiments 0012 Examples of methods and systems for selecting a state of an implantable neurostimulator that is configured to Apr 3 2014 be in at least two states e g therapy disabled and therapy enabled are described herein Embodiments describe a method for unequivocally disabling or enabling the therapy a neurostimulator is programmed to deliver that is uncompli cated and requires only a simple magnet to accomplish Some embodiments also provide a patient with auditory feedback e g one or more different tones when the neurostimulator is in one or the other of its possible states or when the neuro stimulator is susceptible of toggling between states to facili tate a patient s or caregiver s ability to use a magnet to control the state of the neurostimulator 0013 Active implantable medical devices 1 devices that deliver energy or other treatment to the body are typi cally provided with means for communicating with compo nents external of the patient such as inductive telemetry that allows an external host to
59. rk 122 to a central database elsewhere 0043 In some embodiments the inductive telemetry link between the implanted neurostimulator and the programmer or patient remote monitor may be established using a wand not shown by bringing the wand into the transmitting and receiving range of the neurostimulator 106 0044 Several specific capabilities and operations per formed by a programmer 120A 120B 120C or 120D in conjunction with the neurostimulator 106 may include but are not limited to the following specifying and setting the values for parameters in the neurostimulator to adapt the function of the neurostimulator to meet the patient s needs uploading and or receiving data including but not limited to EEG waveforms logs of events detected or data items cor responding to a condition of the device e g remaining useful life of battery that are stored on the neurostimulator down loading and or transmitting program code and other informa tion and commanding the neurostimulator 106 to perform specific actions and or change modes as instructed by a phy sician operating a programmer 120A 120B 120C or 120D hereinafter 120 unless otherwise specifically noted To facilitate these functions a programmer 120 is adapted to receive physician input and provide physician output for example via a keypad or touch screen Data is transmitted between a programmer 120 and the neurostimulator 106 using the wireless telemetry
60. rsistence of a magnetic field The output of a magnetic field sensor is monitored The active implantable medical device is maintained in a first state for so long as the presence of a magnetic field is detected by the magnetic field sensor until a first interval is surpassed Ifthe first interval is surpassed then a determination is made as to whether a second interval has been surpassed If it is determined that the second interval has not been surpassed then the active implantable medical device is transitioned into a second state If it is determined that the second interval has been surpassed then it is ensured that the active implantable medical device is in a predeter mined one of the first and second states 220 222
61. rst interval end point 6 The method of claim 1 further comprising generating at least one alert whenever the magnet is detected and based on the elapsed magnet detection period whenever the active implantable medical device becomes susceptible of either being forced to the first state or toggled from the current state to either the first state or to a different state 7 The method of claim 6 further comprising generating a first alert whenever the magnet is detected based on the elapsed magnet detection period generating a second alert if the active implantable medical device becomes susceptible of being toggled from the current state to either the first state or to a different state and generating a third alert if the active implantable medical device becomes susceptible of being forced into the first state 8 The method of claim 1 further comprising if the at least one magnet removal time is determined generating a magnet removal alert 9 The method of claim 1 further comprising determining the start time when the magnet is detected 10 The method of claim 9 further comprising storing each start time in the active implantable medical device for at least a predetermined length of time 11 A magnet tracking subsystem for an active implantable medical device comprising US 2014 0094876 AI a magnet sensor configured to generate a signal that varies as a function of whether or not the magnet sensor is in the pres
62. storing an electrographic signal or placing a marker in a record of an electrographic signal The communication subsystem 208 and or the magnet tracking subsystem 216 in one embodi ment includes a timer that tracks a time period over which the magnet sensor continuously detects the magnetic field The timer starts tracking time when the presence of the magnetic US 2014 0094876 AI field is detected and stops tracking time when the presence of the magnetic field is no longer detected In one embodiment the communication subsystem 208 and or the magnet track ing subsystem 216 includes comparator that compares an elapsed time calculated by the timer wherein the elapsed time corresponds to the period over which the magnetic field is detected to a first endpoint a second endpoint and an interval extending between the first and second endpoints as will be described below 0057 Typically the communication subsystem 208 includes a telemetry antenna which may be situated inside or outside of the neurostimulator housing enabling the trans mission and reception of signals to and or from an external apparatus via inductive coupling One external apparatus may comprise a programmer 120 that is used by a physician to optimize the performance of the neurostimulator 106 for the particular patient in part by setting the values of the parameters that are used by the neurostimulator 106 to control the delivery of therapy and the response of
63. t such equivalents include both currently known equiva lents and equivalents developed in the future i e any ele ments developed that perform the same function regardless of structure The scope therefore is not intended to be limited to the embodiments shown and described herein but rather is defined by the appended claims 1 A method for selecting a state of an active implantable medical device that is configured to be in at least two states the method comprising monitoring a signal generated by a magnet sensor that indicates whether a magnet is or is not detected relative to the active implantable medical device when the signal indicates that a magnet is detected determining a current state of the active implantable medical device corresponding to at least one start time when the magnet is detected and measuring a period corresponding to the time that elapses beginning with each starting time and con tinuing for so long as the magnet continues to be Apr 3 2014 detected thereafter and ending if at all when the magnet is subsequently removed if the magnet is subsequently removed determining at least one time corresponding to removal of the magnet comparing each elapsed magnet detection period to a first interval characterized by a first interval end point and a second interval characterized by a second interval end point that is different from the first interval end point if an elapsed magnet detection period ex
64. t which the neurostimulator 106 including the magnet sensor 130 has been implanted and then holds it there The magnet sensor 130 may be incorporated inside the neurostimulator housing 104 or secured externally of the housing 104 but in selectable US 2014 0094876 AI operation with the neurostimulator for example in an enclo sure separate from the neurostimulator housing that is imper meable to body fluids The magnet sensor 130 is configured to produce a signal that corresponds to whether a magnet 220 is either present or not present 0048 In some embodiments magnet sensor 130 may be configured with a circuit e g in the active implantable medical device that provides feedback to indicate whether an external magnet is in a position relative to the implant so that the magnet will have the desired effect on the implant The circuit may cause a tone to be generated or a visual cue to be displayed to the patient or caregiver such as on an external device that allows the patient to position the magnet proxi mate to the implant for the best interaction between the mag net and implant 0049 When the implanted magnetic sensor associated with the active implantable medical device senses the pres ence of a magnetic field the active implantable medical device may be configured to undertake different behaviors based on the period of time for which the implant continu ously senses the magnet For example if the patient merely sw
65. tate from the therapy disabled state 0096 Referring now to the bottom panel 512C of FIG 6 if the neurostimulator 106 continues to detect the presence of the magnetic field throughout all of the magnet toggle interval 504 and all of the magnet force offinterval 508 1 from the time t a r 502 through and including the time t 510 then the long low tone 526 will be generated for the entirety of the magnet toggle interval 504 from the timet 502 to the time tenai 506 the beeps 528 will be generated during the time period 509 between the magnet toggle interval endpoint time tai 506 through the magnet force off interval endpoint time Apr 3 2014 tva 510 and then the long low tone 526 will be generated again as soon as the magnetic field has been detected long enough to force the neurostimulator 106 into the therapy disabled state When the neurostimulator 106 ceases to detect the magnetic field at time tposyorceog 514C in FIG 6 neither the long low tone 526 nor the beeps 528 are gener ated 0097 FIG 6 also illustrates the opposite case for the vari ous timing scenarios for when the neurostimulator 106 detects and ceases to detect the presence of a magnetic field Referring again to the top panel 512A of FIG 6 if the neu rostimulator 106 detects the presence of a magnetic field at time ta 502 and the neurostimulator 106 is then in a therapy enabled state then the patient will begin to hear
66. the implant for at least as long as the magnet force off interval 508 the tone associated with the therapy disabled state may be generated for a few seconds after that interval has been exceeded to confirm that therapy indeed has been disabled and it is all right for the patient to remove the magnet Other possibilities for the auditory feedback will be readily apparent 0104 It should be appreciated that while various embodi ments have thus been described herein with regard to an neurostimulator 106 embodiments may be integrated within all sorts of active medical implantable devices including but not limited to the following implantable medical devices delivering treatment in the form of drug delivery optical energy and mechanical energy implantable medical devices that may be controlled with means such as mechanical pres Apr 3 2014 sure or electrical fields and implantable medical devices capable of operating in more than one mode or with more than one setting including both simple on and off modes and more complex cases in which modes correspond to various stimulation setting or types of therapy delivery 0105 FIG 7 isa flow diagram of elements of a method 700 for selecting a state of a neurostimulator 106 in accordance with an embodiment The two states are therapy enabled and therapy disabled It will be appreciated that in other embodiments the states of the neurostimulator 106 affected by
67. the neurostimula tor 106 to the presence of a magnetic field 0058 Alternative embodiments of the communication subsystem 208 may use an antenna for an RF link or an audio transducer for an audio link to the patient 124 in order to provide indications of neurological events a system s status and or other relevant information 0059 In a responsive neurostimulator the control module 108 also may include a detection subsystem 202 which oper ates on signals corresponding to data sensed from the patient and routed from the electrodes 118 through the electrode interface 200 The electrode interface 200 may act as a switch to select which electrodes 118 to sense physiological data from and may encompass other functions such as signal conditioning and processing including amplification and iso lation 0060 The detection subsystem 202 may include an analyzer function The EEG analyzer function may adapted to receive EEG signals from the electrode 118 through the electrode interface 200 and to process those EEG signals to identify neurological activity indicative of a sei zure an onset of a seizure and or a precursor to a seizure 0061 The detection subsystem 202 also may contain fur ther sensing and detection capabilities including but not lim ited to parameters derived from other physiological condi tions such as electrophysiological parameters temperature blood pressure movement etc 0062 The detection
68. the other hand if at block 720 the neurostimulator 106 no longer detects a magnet and at block 735 the magnet toggle interval 504 has not been exceeded or has not ended then the neurostimu lator 106 does nothing That is ifthe neurostimulator 106 was US 2014 0094876 AI in a therapy disabled state just before the presence of the magnet was first detected at block 710 and the endpoint of the magnet toggle interval 504 is not reached before magnet is no longer detected e g the magnet is taken away from the implant site then the neurostimulator 106 remains in the therapy disabled state If the neurostimulator 106 was in a therapy enabled state just before the presence of the magnet was first detected at block 710 then the neurostimulator 106 remains in the therapy enabled state when the neurostimu lator 106 ceases to detect the presence of the magnet before the magnet toggle interval is up 0110 Thus if a patient or a patient s caregiver wants to ensure that an implanted neurostimulator 106 is in a state in which it is not able to deliver therapy e g electrical stimu lation the patient or caregiver can accomplish this simply by applying the magnet for at least as long as the magnet force off interval 508 Once the patient is assured that the implant is in a therapy disabled state the neurostimulator 106 can be returned to a therapy enabled state by removing the magnet from the neurost
69. to a therapy disabled state if the neurostimulator 106 was not in that state already and 2 removing the magnet and reapplying the magnet for longer than the magnet toggle interval 504 longer than the endpoint at the time 506 but removing the magnet again before the end of the magnet force offinterval 508 1 removing the magnet again between the end of the magnet toggle interval 504 and the end of the magnet force off interval 508 between the endpoint at the time t 506 endpoint at the time 510 US 2014 0094876 AI 0080 The length of the magnet toggle interval 504 and the magnet force off interval 508 and the effect each interval has relative to the patient s or caregiver s use of a magnet 220 may be fixed as in manufacturer settings for the device and set forth in a patient manual provided at the time the active implantable medical device is implanted Alternatively the instructions relevant to using a magnetic field to ensure that an active implanted medical device is either in one state or another may be made available over a website or communi cated in some sort of training related to the implant In some circumstances a patient or caregiver may be able to call a Help Desk or a doctor s office and ask someone to guide them through the procedure to first make sure the implant is in one state e g the therapy disabled state and if desired then to make sure the implant is in the othe
70. tor 106 from a state in which therapy is disabled to a state in which therapy is enabled or vice versa 0067 Depending on how long a magnet sensor 130 detects the presence of a magnetic field the magnet tracking sub system 216 may cause the neurostimulator 106 to stay in the state the neurostimulator 106 was in just before the presence of the magnet was detected transition from the state the neurostimulator 106 was in just before the presence of the magnet was detected to a different state or transition into or remain in as the case may be a predetermined one of the two states In the example described herein the two possible states of the neurostimulator 106 into which the magnet can transition the neurostimulator 106 are a state in which therapy is enabled and a state in which therapy is disabled 0068 It will be appreciated that it may be desirable for the neurostimulator 106 to behave in the presence of the magnet by transitioning to and from states other than therapy enabled and therapy disabled states for example depend ing upon the application of the neurostimulator 106 If the neurostimulator 106 is being used to deliver a form of con tinuous therapy to the patient use of the magnet may cause the neurostimulator 106 to transition from a state in which it is delivering a higher level of stimulation to a state in which it is delivering a lower level of stimulation or a state in which it is in a stand by mode In oth
71. urity turned off the therapy or not 0022 Still other active implantable medical devices are known in which a stimulation therapy can be toggled between on and off if the implant detects a magnet For example if the stimulation is it will be toggled off when a magnet is detected and vice versa 1 if the stimulation is off it will be turned when a magnet is detected This toggling behavior allows stimulation to be disabled without the patient or caregiver having to hold the magnet in place near the implant the whole time However if the patient or caregiver is not sure what state the implant is in just before the magnet is used to toggle the state then it follows that the patient will not be sure what state the implant is in after the toggle Again in many applications of active implantable Apr 3 2014 medical devices the patient normally does not feel the therapy he or she is receiving so the patient will not neces sarily be able to tell whether the implant is delivering therapy or not 0023 For example if the application is a neurostimulator configured to deliver continuous electrical stimulation therapy to treat symptoms of a movement disorder such as tremor the patient may not be able to tell whether stimulation is on or off if the patient doesn t happen to be experiencing any symptoms directly after using the magnet When the patient later experiences symptoms the patient
72. use of the magnet may be different such as simple on and off states and standby states sensing only and sensing and stimulation states and so on and so forth 0106 With reference now to FIG 4 and FIG 7 a neuro stimulator 106 according to embodiments includes a commu nication subsystem 208 which enables communication between the neurostimulator 106 when implanted in a patient and the outside world The communication system 208 includes a magnet sensor 130 for example provided on a printed circuit board within a neurostimulator housing or otherwise associated with a control module 108 of a neuro stimulator 106 The magnet sensor 130 generates an output signal when the magnet sensor 130 detects the presence of a magnetic field such as from a magnet 220 that is provided to the patient The magnet sensor output is processed and used by a magnet tracking subsystem 216 to determine whether and if so how to change the behavior of the neurostimulator 106 based on the presence of the magnet 0107 In FIG 7 at block 705 the method and system monitors to determine whether the presence of a magnet is detected This may be accomplished for example by moni toring the output of the magnet sensor 130 When at block 710 the neurostimulator 106 detects a magnet e g at time trar 502 in FIG 5 then at block 715 the magnet tracking sub system 216 begins to track what happens next in terms of how long t
73. ware object state at least one condition that causes transition of the software object into a different software object state and the activities of each software object that occur when the software object transitions into a different software object state a timer configured to keep track of the amount of time the sensor detects the magnetic field uninterrupted in rela tion to at least two of the software object states in the set of possible magnet tracking software object states and an interface for passing messages and information from the magnet tracking software object to at least one other software object that controls whether the active implant able medical device delivers or does not deliver a therapy 17 The system of claim 16 the magnet tracking software object further comprising a first software object state corresponding to a condition when no magnetic field is detected by the sensor second software object state corresponding to the condi tion when a magnetic field has begun to be detected by the sensor a third software object state corresponding to the condition when the timer indicates that a magnetic field has been detected by the sensor for longer than a first interval and a fourth software object state corresponding to the condi tion when the timer indicates that a magnetic field has been detected by the sensor for longer than both a first interval and a second interval the active implantable medical device
74. with sensing or stimulation elements other than electrode s 118 0039 For example if the application of the responsive neurostimulation system is to treat epilepsy and a seizure focus previously has been localized for the patient the elec trodes can be implanted at locations intended to capture sig nals generated at or near the seizure focus Commonly a lead bearing electrodes e g lead 114 at a distal end thereof is implanted through a hole 132 drilled in the patient s skull usually referred to as a burr hole because of the cranial drill used to form it The proximal end of the lead is then con nected to the neurostimulator to put the electrodes in electri cal communication with the neurostimulator It will be appre ciated that elements other than electrodes may be configured and used to sense physiological data from the patient other than electrographic signals such as optical sensors voltam metry sensors oximetry probes temperature probes and the like 0040 The housing 104 may be fabricated from a biocom patible material such as but not limited to titanium Tita nium is light extremely strong and biocompatible Other biocompatible materials may additionally or alternatively be utilized in the fabrication of the housing 104 0041 The housing 104 may also enclose a battery 110 or other source of power for the neurostimulator as well as a physical component or components that allow the neuro stimulator t

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