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1. 0 2 4 6 B 10 12 14 ms Latencies ms IPL ms I lll 14 MA 80 6 0 a0 E TTD y T 10 T 50 Ti 70 click level dB nHL 3 Cochlear hearing loss Click evoked ABRs in a patient suffering from a moderate high frequency cochlear hearing loss at 70 60 50 40 and 30 dB nHL stimulus levels In comparison to the normally hearing subject ABRs appear with lower amplitude and slightly increased wave V latency ABR threshold 1s reached at 30 dB nHL The prolongation of latency at low stimulus levels corres ponds to the propagation time of the travelling wave along the non functioning basal part of the cochlea at these levels Stimulus rate was set to 20 Hz vertical electrode montage 19 22 ABR e mu 16 18 PTA Result Wave Y SOOM tw E En mn Ss Ho de AG latency ms 0 2 4 6 B 10 12 14 ms Latencies ms IPL ms 1 11 14 MA TO 5 TO fle 1 click level dB nHL Click evoked ABRs in a patient suffering from a severe high frequency cochlear hearing loss at 80 70 60 50 and 40 dB nHL stimulus levels ABR threshold 1s reached at 60 dB dB nHL approximately corresponding to the hearing loss at high frequencies Low frequency thresholds can not be assessed Stimulus rate was set to 20 Hz vertical electrode montage 47 6 ABR How to use Wave V T50ny 80 E Audiogram tee 0 5 1 2 3 4 6 6 125 16k latency ms 0 2 4 6 6 10 12 14 16 ms Latencies ms IPL ms I I2. Please note that order of the markers is always preserved with a minimum distance of 0 5 ms Back leaves the screen without saving new peak positions 45 6 ABR How to use Enter confirms the changes and goes back to the regular ABR result display When opening a result from result view you have the same editing options as described above after a measurement 6 3 ABR case examples 1 Normally hearing subject Click evoked ABRs in a normally hearing subject at 50 40 30 20 and 10 dB nHL stimulus levels ABRs are measurable down to 10 dB nHL Wave V latency increases and wave V amplitude decreases with decreasing stimulus level Wave V latencies are within normal range 16 12 ABR e Ma 18 51 PTA Result o Wave V 500 50 rh part Audiogram 40 a ee ATEN EE A e latency ms o 2 4 6 8 10 12 14 ms Latencies ms IPL ms EMI 1 7 MAL 50 62 50 50 A click level dB nHL 2 Conductive hearing loss Click evoked ABRs in a patient suffering from a conductive hearing loss at 80 70 60 50 and 40 dB nHL stimulus levels Wave V latency is increased being out of normal wave V latency range ABR threshold is reached at 50 dB dB nHL corresponding to the hearing loss at high frequencies Stimulus rate was set to 20 Hz vertical electrode montage 46 ABR case examples 17 38 ABR e EF 16 38 PTA Result gt Wave Y 5p0ny 80 eee Z DIT OASI Audiogram 70 latency m s
3. edge The traffic light symbol to the left of each response indicate its significance If Auto Proceed is selected the device will automati cally proceed with the next measurement when significance of the cur rent measurement was reached which is indicated by the green light You may proceed at any time by pressing the skip button or wait until the maximum recording time per response is reached After the maximum recording time is reached the device proceeds to the next stimulus level By pressing the pause button the measurement is paused and the pause button changes to the play button To continue press play During the measurement the electrode impedance is measured periodi cally If the value is too high the measurement is paused and a mes sage Electrode impedance is too high The test will now pause You may re place the electrodes and continue the test is shown Perform measurements 13 54 ABR lt 2 Hu KODIR 0 2 4 6 8 10 ms EEG ES impedance 1 5k Progress ZT mM 1 6k 16 13 ABR lt H gt 0 2 4 6 8 10 12 14 ms Latencies ms IPL ms I III I V M1 50 50 ES 40 gt 40 30 20 10 0 2 4 6 8 10 12 14 ms Latencies ms IPL ms I III I V M1 0 62 50 In this case re place the electrodes and press the play button to con tinue within the maximum recording time per response When the measurement has f
4. Auto Proceed Auto Proceed will proceed the measurement at the next stimulus level when significance is reached for the current measurement Select Auto Stop Auto Stop will abort the test sequence 1f no significant response could be recorded for two consecutive stimulus levels Select stimulus levels At the level selection screen 1 to 5 levels can be selected Measure ment will be started at the highest stimulus level ABR amplitude decreases and latency increases with decreasing sti mulus level In normal hearing subjects wave V latencies varies bet ween about 5 6 ms 80 dB nHL and about 9 ms 10 dB nHL Stan dard deviation of latency is low at the higher stimulus levels approx 0 2 ms at 80 dB nHL and high at the lower stimulus levels approx 0 7 ms at 10 dB nHL Initial stimulus levels higher than 70 dB nHL have to be confirmed prior to measurement Perform measurements 13 40 ABR lt r MH Stimulus Averages Plot Range Rate A A A Vv Y 100 0ms Time per trace 2000s Total time 10000s Inter Stimulus Interval 13 34 ABR E gt Age group for normative latencies Newborn O 2 months 6 months O 12 months Adult Don t show normatives O Ask before test 13 41 AB R lt r i gt NEURO 10HZ Rea Select the stimulus rate plot range and the number of averages per response The inter stimulus interval the test duration per response and
5. 6 ABR How to use Auditory brainstem responses ABRs recorded from electrodes placed on the scalp represent the far field of potentials generated by the fiber tracts and nuclei of the ascending auditory pathway between the cochlea and the brainstem The ABR latency epoch consists of up to seven prominent wave peaks which appear within the first 10 ms Commonly ABRs are elici ted by transient stimuli click tone burst chirp ABRs represent the sum of synchronized neural activity of the ascending auditory pathway Wave I and II stem from auditory nerve wave III from cochlear nucleus wave IV and V from lateral lemniscus and inferior colliculus brain stem and wave VI and VII from sub cortical regions Due to the fact that the velocity of the traveling wave running into the cochlea is highest in the basal region click evoked ABRs mirror mainly the activity of basal high frequency cochlear regions This is also true for low frequency tone bursts and chirps when high stimulus levels are applied Wave V has the highest whereas wave I the lowest amplitude Wave amplitudes decreases wave latencies increases with decreasing stimulus level ABRs are a common clinical tool in audiology and neurology Also ABRs are used for new born hearing screening when elicited at a distinct screening stimulus level e g 35 dB nHL Conductive and cochlear hearing loss exhibit different wave amplitude and latency patterns Especially wave V latency and threshold ar
6. II 14 MA 80 8 5 80 T 8 6 FO 60 6 0 60 50 50 40 40 30 40 50 60 70 90 click level dB nHL Click evoked ABRs in a patient suffering from a pan tonal frequency cochlear hearing loss at 70 60 50 40 and 30 dB nHL stimulus levels At all stimulus levels with exception of the lowest one latencies are within normal range ABR threshold is reached at 40 dB dB nHL Stimulus rate was set to 20 Hz vertical electrode montage Wave V Audiogram O25 05 1 34 b 8 125 16k latency m s 0 2 4 6 8 10 12 14 ms Latencies ms IPL ms PMI 14 M2 T 28 T 60 6 1 60 50 64 50 40 A pl 40 30 30 30 40 50 60 10 90 click level dB nHL 4 Retrocochlear hearing loss Click evoked ABRs in a female patient with neural disorders at 80 dB nHL stimulus level ABR wave pattern 1s different compared to the normally hearing subject and the patients with cochlear or conductive hearing loss with respect to I V IPL I V ILP is prolonged 4 4 ms due to disturbed synchronisation of nerve fibers exceeding normal I V interval female mean 3 8 ms 0 2 ms standard deviation male mean 4 0 ms 0 2 ms standard deviation Stimu lus rate was set to 10 Hz horizontal electrode montage 48 ABR case examples Soon a0 m 0 2 4 6 8 10 12 14 16 ms Latencies ms IPL ms AMI 12 MAL 80 1 7 44 6 1 80 27 44 17 49
7. ac E open 13 50 ABR Hr j Impedance Progress ppm aji Mm 1 6k 13 52 ABR LF 80 A El e O 60 40 0 2 4 6 8 10 ms EEG PU Impedance 1 5k Progress PA E 1 6k 13 54 ABR e gt 84 ANA at c Ti s Electrode impedance is too high The test will now pause 41 You may re place the electrodes and continue the test S OK i 44 Before ABR measurement starts electrode impedance is checked When the impedance is within an acceptable range below 12 kQ a play button appears in the footer To indicate good impedances the color of the impedance value will turn green if it is below 6 kQ Please note In neonates impedance may be higher than 6 kQ because of tenderness of the skin Also unbalanced impedance affects the qua lity of ABR measurements By pressing the play button ABR measurement at the highest selec ted level is started If the play button is not pressed or the impedance remains to high the device stops measuring after some seconds In this case place the electrodes again and restart the test The currently measured response is shown 1n blue All other responses are shown in gray The right top corner indicates the current selected scale 100 to 2000 nV It can be modified by wiping up and down inside the graph area after the measurement or in the result view mode During the measurement the selected levels are shown on the left
8. ack IMA IM V Print w Info uu III Set 38 Preparation of the patient to be tested 6 1 Preparation of the patient to be tested Advise the subject to lay as comfortable as possible to avoid muscle activity Clean the skin where the electrodes will be placed Place electrodes Fig la Screen pictogram Fig 1b Cable pictogram There are several possibilities to place the electrodes The position of the electrodes affects waveform morphology and latency Best elec trode position for yielding maximum wave amplitudes is vertex and ipsilateral mastoid vertical montage Alternatively to the vertex posi tion forehead position for placing the vertex electrode is possible see Fig la and 1b However in this case ABR amplitude is slightly decreased Despite this fact forehead is preferred in practice especi ally in patients where vertex electrode placement is inconvenient because of hairs Wave I amplitude may be larger in a horizontal montage mastoid to mastoid than in the standard vertical montage vertex to mastoid Reference electrode black is usually placed on the cheek Since Sentiero provides one channel mastoid electrode cable must be changed when using vertical montage of the electrodes If mastoid electrode is not changed ABR is decreased in amplitude at the ear where mastoid electrode cable is connected to the contra lateral ear Common placement of the electrodes for audiological testing Re
9. cells along the cochlea for getting highest neural activity on the nerve fibers The band width of a click see frequency domain Fig 2b blue line depends on stimu lus duration see time domain Fig 2a blue line The shorter the click the higher is the band width and with that the synchrony of neural activity on the auditory pathway However synchrony is decreased in the more apical regions of the cochlea in accordance with the decrease of the travelling wave velocity In contrast to the click the chirp is a long lasting stimulus which starts with low and ends with high fre quency signals see time domain Fig 2a red line Using this rising frequency chirp the decrease of the travelling wave velocity along the basilar membrane is compensated resulting in an enhancement of the synchrony of neural activity and with that in higher response amp litudes Chirp provides a broader frequency band compared to that of the click see frequency domain Fig 2a blue and red line Select polarity Condensation C Rarefaction R or Alterna ting A Single polarity stimuli C or R produce different initial movement of the basilar membrane Initial firing of the nerves coincides with R sti muli resulting in different wave latencies and amplitudes with C and R Thus different waveform morphology appears when using single or alternating polarity clicks Single polarity click stimulation may evoke wave I with higher ampli tude Ho
10. d Mastoid Black e Cheek MYLA Ba OCET 6 2 Perform measurements de i After placing the electrodes electro acoustic transducers headphones or insert phones have to be fitted Important Please make sure that the red transducer is placed at the right ear and the blue transducer is placed at the left ear Plug the ABR cable connector in the white jack Then connect the electrodes with the colored clips as described above red mastoid white vertex or forehead black cheek 39 6 ABR How to use Start the measurement module by pressing ABR Select one of the presets by pressing the appropriate button By pressing Right or Left the test ear is selected and the test starts q P Alternatively the selected preset can be edited by pressing the settings button There are 4 settings pages Each has to be confirmed with enter in order to store the set tings magniture dB Perform measurements 13 30 ABR eL Stimulus Click Chirp Condensation Rarefaction Alternating W Jitter Y Masking noise C Auto Proceed C Auto Stop 1 1 5 time ms Fig 2a Time domain 1000 2000 30 00 4000 5000 600 frequency Hz Fig 2a Frequency domain 0 7000 9000 Select stimulus type Click or Chirp Both clicks and chirps are broad band stimuli Broad band stimuli are used to stimulate as many as possible sensory
11. e used for audiological diagnostics in children or handicapped persons who are not able to reliably report on their hearing disability The inter peak latency IPL between wave I and V represent the neural transmission time between cochlea and brainstem IPL is therefore used for assessing retrocochlear pathology eighth nerve and low brainstem lesions It is important to note that due to the maturation of the neural pathway IPL varies during the first year of life The influence of age on ABRs in the elderly is a matter of controversy While some authors have reported a change in IPL others claim that there is no delay in neural transmission time with ageing Also no significant corre lation was observed between the score of speech discrimination tests and IPL Sensitivity of ABRs is quite low below 1000 Hz due to poor synchrony of neural aktivity in the apical region of the cochlea Click evoked ABR does not allow direct frequency specific assessment of hearing loss Click evoked ABRs exhibit nearly normal patterns in patients with low and or mid frequency hearing loss Low frequency stimulation at high stimulus levels will also stimulate basal sensory cells Thus assessment of low frequency functionality 1s only possible at low stimulus levels For getting more frequency specific information DPOAE at a 37 6 ABR How to use hearing loss up to 50 dB or tone pip and chirp evoked ABR have to be used However when applying low frequenc
12. inished the ABR result panel is displayed which shows the responses at all selected stimulus levels You may modify the scale by wiping up and down inside the graph area The traffic light symbols to the left of each response indicate its statistical significance providing a suggestion for the responses to be valid If wave peaks were marked the available absolute latencies wave I wave III wave V and relative latencies IPL will be shown in the lower panel Different IPLs can be selected Wave I III wave II V and wave I V Press the table area to display either latencies recording parameters or quality data The footer shows now different buttons Back I II V print and info Print will print the results to the label printer Back leads to previous screen Info will show the online help I HI V enters the edit mode where you can mark peaks In the peak settings mode you may mark wave peaks in each response manually The active response can be selected by pressing the buttons to the left of each response 11 V selects the marker to be modified indicated the red point on top of the marker Set makes a peak marker permanent so that it will be stored with the test The marker will turn green to indicate this Left right moves the selected marker to set the latency of the corre sponding wave You may also set the marker by pressing on the desi red latency position
13. the esti mated overall test duration will be shown as a result of the settings Changes in stimulus rate affect ABR latency and amplitude With increasing stimulus rate wave amplitudes decrease and wave latencies increase Please note Wave I latency is less affected resulting in an increase of inter peak latencies with faster rates For assessing neural disorders a rate of 10Hz is recommended If wave V is the only com ponent of interest e g threshold determination faster rates can be used With increasing number of averages quality of ABR measurement is increased In quiet subjects and at good measuring conditions 2000 averages may be sufficient If there is high muscle activity high elec trode impedance ambient acoustical and electrical noise the number of averages has to be considerably increased especially at close to threshold stimulus levels Select age group Several groups can be selected Newborn 2 month 6 month 12 month Adult The selection will only affect the normative latency range which is dif ferent for the different age groups Latency ranges are shown with the responses Further age group options Don t show normatives Ask before test By pressing Edit Preset Name the preset can be renamed Type in the new preset name by using the screen keyboard Confirm your input with enter Continue Measurement 43 6 ABR How to use 13 56 ABR lt r Hi y Impedance Progress MEN v
14. wever when using single polarity clicks the electrical signal of the electro acoustic transducer interferes with the ABR Therefore A click stimuli are preferred especially when using headphones When using insert phones electrical artifacts are lower Select Jitter Jitter will add a small random change in stimulus rate which can reduce the sensitivity to certain electrical interference ABR amplitude is known to be decreased at a constant stimulus rate due to adaptation By enabling Jitter adaptation is reduced Select Masking noise Masking noise will mask the contralateral ear This is done to de 41 6 ABR How to use 13 39 ABR lt r Ht Levels select 1 to 5 O 90 dB nHL WF 80 dB nHL WR 70 dB nHL WR 60 dB nHL WF 50 dB nHL WR 40 dB nHL O 30 dB nHL 20 dB nHL 10 dB nHL 85 dB nHL 75 dB nHL 65 dB nHL 55 dB nHL 45 dB nHL 35 dB nHL 25 dB nHL 15 dB nHL o 00 0 0000 0 5 dB nHL 13 41 ABR HD The initial stimulus level will be higher than 70 dB nHL Do you want to continue Yes 42 _No synchronize the stimulus related neural activity on the auditory pathway of the non tested ear which might be stimulated by cross hea ring It is recommended to always use this option especially in cases of asymmetrical hearing loss The masking level 1s controlled by the device and depends on the stimulus level and the electro acoustical transducer used Select
15. y stimulation at high stimulus levels the basal region of the cochlea is also stimulated Thus frequency specificity of ABRs is restricted Compared to ABRs audi tory steady state responses ASSRs available in 2012 provide better frequency specificity In patients with hearing loss wave I may be missing In these patients determination of IPL is not possible and thus neural disorders can not reliably be assessed Correct placement of elec trodes is crucial in order to yield optimal ABR patterns Due to the fact that electro magnetic fields have impact on ABRs proper measuring conditions are essential Proper measuring con ditions are present 1f ABRs are measurable down to 10 dB nHL in a young normally hearing subject Intended clinical applications of ABRs are as follows Topological diagnostics assessment of peripheral and central sound processing on the auditory pathway up to the brainstem along with other audiological tests Identification of neural disorders eight nerve and low brainstem lesions on the audi tory pathway Non frequency specific determination of hearing loss within mid frequency region when using clicks Determination of hearing loss within different frequency regions when using low mid and high frequency chirp stimul1 In the following the use of ABR test is described in detail Corresponding button names and icons are as follows ABR ABR A Settings Enter F Play T Pause Skip gt Left right q B
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