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SAMPLE ABR REPORT Auditory evoked potentials were elicited using .1 msec rarefaction clicks presented monaurally at 90dBHL at rates of 21.1 and 71.1 clicks per second. Dual channel recordings were made with test electrodes on each mastoid. Tracings were characterized by clearly formed and repeatable wave peaks. The absolute and inter-peak intervals were within normal limits.11 There were appropriate latency shifts with increased repetition rates?f No significant inter-aural differences were noted. ~\hc~-t lv tk\ nO dan~ ct1 nr tuMe{trrtt ~ ~ 01, ~ n,o,( fX>~ . Impressions: ABR test results were within normal limits bilaterally. TABLE 6.2. Guidelines for a Test Protocol for Clinical Measurement of the Auditory Brainstem. Response (ABR) PARAMETER SELECTION n RATIONALE/COMMENT I )> ::'m=! Stimulus Parameters ;;o Transducer Insert earphone Type Duration Polarity Click 0.1 ms {100 /-LS) Rarefaction Rate > 20/sec, e.g., 27.3 > 90/sec, e.g., 91 .1 Intensity Repetitions Masking Mode Variable in dB nHL Variable Rarely needed Monaural There are a dozen good reasons (see Table 3.3) Bone conduction is also feasible Optimal, but tone bursts also feasible (see Chapter 8) Best for transient (synchronous firing) onset Larger amplitude and shorter latency than condensation Change polarity if waveform is suboptimal Faster rate saves time Slow the rate as needed to enhance the response An odd number reduces chance of interaction with 60 Hz High rate may be increase likelihood of detecting retrocochlear dysfunction in neurodiagnostic ABR High for neurodiagnosis Perform latency-intensity function for threshold estimation As many or few signal presentations as needed for an adequate signalto-noise ratio {SNR) Repetitions are another term for sweeps (see below) Only if ABR is abnormal and no wave I is detected Ear-specific information is typically desired clinically Acquisition Parameters Electrodes Non inverting Inverting Ground Filters -- - - - - - HP (high pass) LP (low pass) Notch Amplification Analysis time Prestimulus baseline Sweeps {# stimuli) Fz Ai Fpz 30Hz 3000Hz none 100,000 15 ms - 1 ms Variable A high forehead site is preferred to the vertex Ipsilateral earlobe; a TIPtrode is sometimes indicated A low forehead site is convenient for the common electrode Low frequencies contribute importantly to the ABR, and are essential for detection of an ABR from infants 1500 Hz if there is excessive high-frequency artifact Avoid, as the notch removes important low-frequency energy in the ABR spectrum x 100,000 is equivalent to sensitivity of ± 25 or 50 !-LV Encompasses ABR in all cases (except low-frequency tone-burst signals) Information on response quality Whatever is needed for good SNR m )> IJJ ;;o ~ ~ ~ m ;;o _Vl 'U ;;o ~ 0 0 (') r _Vl )> z 0 'U ;;o 0 (') m 0 c ;;o m l/1 o- t&-~,"'~ 4/~er-,..~ pJlov+1 NORMATIVE DATA- ABR PROTOCOL Table 2. Summary of latency values for auditory bralnstem responses elicited With dick and tOOl~ bUrst stimuli at selected intensity levels. LATENCIES (ms) v Ill L R L v R L R l R 26 26 26 25 24 .., n 26 26 25 3 E mean 1.64 1.7 4.06 4.09 . 6.18 6.16 6.72 8.72 1.40-1.91 1.5-2.0 3.4 -4.37 3.65-4.46 5.54-6.71 5.54-6.62 7.85-9.92 7.58· 9.92 6.06-6.30 6.07-6.26 8.52-8.92 8.45-8.99 ::l +l i U) ..10: min· .2 0 aa•;. Cl n 16 15 16 22 18 17 16 mean 1.92 1.97 4.31 6.5 6.47 1.19 6.04 .a Gl c 1.46-2.36 1.55-2.24 5.9-7.37 6.02· 7.73 7.4-8.99 7.3. 1.78 .. 4 4 3.46 3.63 f::l ... 0 r! ::l .a Gl c 2 10 6.01 6.24 7.98 7.66 10.15 9.7 2.96-4.56 5.81-6.30 6.18-6.30 7.4-9.74 7.22· 7.66 1.84-11.48 1.57-11.22 2.95-4.31 ---- 5.72-6.30 6.12-6.36 0 1- ~ ... ..10: 95%CI 3.11-3.81 ... ' ·- ... --~ ~-~~ '"·-~- ~~ ...... ~~ · ~~ ~ L 0 N R . 7.57-8.39 I" ' - • - 7.42-7.90 - --· - __ ~ _, 9.62-10.69 8.89-10.50 .. ---- - - - -- --.. . ---- -- --....,.... ---~r -··· IIJt.T:'l~~~GtT.'~-~(,"I=r~ :r.c-·:;"~· ...."A".. __~,.....,r.r:;·=a-.-.. --.-~ L b;~~ ~~ -~~Jt.-t,.; ":_:_3,,_, ?J ~ .1..JJ~J.._-~L~ '';..:.. L IR A 1.... ... • L R L R ; ~:r: n 10 12 12 ' 14 15 12 12 11 I!! ::l .a Gl c mean 9.67 9.53 10.22 j0.03 11.51 11.45 12.1 11.65 min-max 8-11.50 1.09-13.22 9.74-15 1.09-13.78 .. 6.68-11.62 7.48-12.82 7.8L 11.6a 10.1 ·13.54 0 1- 95%CI 8.89-10.45 8.64- 10.41 9.48-10.96 9.50-10.56 10.93 -12.08 10.62-12.27 11.18-13.02 10.55-12.75 I II 246 PART Ill AUDITORY BRAINSTEM RESPONSE (ABR) AND AUDITORY STEADY-STATE RESPONSE (ASSR) I ' TABLE 7.1 Selected Auditory Brainstem Response Measurement Problems and Possible Solutions See text for discussion. I SYMPTOM POSSIBLE PROBLEMS POSSIBLE SOLUTIONS No display Technical Equipment won't average Set up error More than one response in analysis time No response Stimulus rate vs. analysis time incompatible verify the system pbwer is on verify the power co(d is plugged in verify monitor (scr~en) power is on verify adequate mo'nitor brightness verify an evoked prpgram is loaded consult the equipn1ent manual verify stimulus repetitions are not at "0" verify stimulus duration is not "0" verify stimulus rate 'not too fast for the analysis time verify all measure~ent parameters restart computer I consult equipment jmanual slow stimulus rate ~o the lSI is longer than the analysis time shorten analysis ti"?e to less than lSI the lSI for a click is f!nalysis time/rate perform a listening check verify the correct tr9nsducer is used verify the test ear is·correct verify correct electrode sites obtain an audiograr,n if feasible increase stimulus i11tensity to maximum attempt bone-conduction stimulation 1 check gain alternate polarity 1 use insert earphon~s to separate transducer from electrode verify electrode wires are not near power cords verify electrode wirJs are not near earphone wires reduce stimulus intensity use post-stimulus time delay stimulus artifact is expected for bone-conduction stimulus attempt to relax patient encourage sleep sedate patient J ~~!~~ ~~~~Js;ss filte lcutoff frequency No stimulus Improper electrode site or array Severe hearing loss Excessive early artifact Large, slow artifact . Inadequate amplification Stimulus interference Muscular artifact 1 Poor waveform morphology High-frequency loss or retrocochlear dysfunction? Excessive noise, spikes, or small fluctuations in waveform High-frequency electrical interference Small or no wave I High-frequency hearing loss verify artifact rejection is on increase stimulus intensity slow stimulus rate : change stimulus polarity increase number of sweeps record multiple replicated waveforms sum replicated waveforms use click versus tone-burst stimuli open filter settings I analyze a prestimult;.s baseline verify that the artifaCt rejection is on rule out electrical dJvices and lines verify good ground I alter stimulus rate ' lower low-pass filter alter electrode array: increase sweeps verify adequate electrode impedance increase intensity decrease rate verify ipsilateral electrode site use earlobe versus mastoid electrode i \ CHAPTER 7 ABR ANALYSIS AND INTERPRETATION 'I ' ' POSSIBLE PROBLEMS SYMPTOM Small or no wave I (continued) I' POSSIBLE SOLUTIONS i ,Delayed wave I Conductive hearing loss ~Bifid wave I f' Which peak is used ~or latency calculations? , iSmall or no wave ''·· II or Ill High-frequency hear ng loss or brainstem dysfunc ion ":. latency ) ~ I l II ' ' n~ 1)ndistinct wave V Latency calculation f' (;, pelayed wave V no wave I ~)atency, Peripheral or brainst~m dysfunction? ! ' j :. ' ,. .~rominent wave VI Really wave V? I I ;'t ·'1 wave V Really wave IV? i,'t ~:ij (Delayed wave 1-V f,rlatency Brainstem dysfunctio ? ;· I \i I r·~~hort wave 1- V use an ear-canal electrode (~.g., TIPtrode) use TM or n electrode 1 change stimulus polarity to rrrefaction horizontal electrode array use click versus a tone burst i lower high-pass filter increase the number of sweeps (averages) ·obtain audiogram · Perform an air- versus bone-conduction audiogram bone-conduction ABR immittance measures increase intensity decrease intensity change polarity ECochG electrode horizontal electrode array obtain audiogram increase stimulus intensity horizontal or noncephalic electrode array change.stimulus polarity ' TI or TM electrode I obtain audiogram \ increase stimulus intensity lower high-pass filter setting raise low-pass filter setting use noncephalic electrode arr . y analyze latency-intensity function rule out inadvertent ipsilateral' masking multiple replications change polarity obtain audiogram increase intensity rule out crossover response (masking) see wave I enhancement tech~iques above I document young age lower stimulus intensity \ use contralateral masking I use horizontal or noncephalic ~lectrode array use contralateral and noncephalic electrode arrays change stimulus intensity leveli compare with waveform from other ear rule out hypothermia document young age calculate interear latency difference verify wave V identification (se~ techniques above) use gender-matched normativ~ data obtain audiogram j rule out high-frequency hearin~ loss rule out hyperthermia l wave I delayed? bifid wave I? use gender- and age-matched normative data verify wave V versus IV identification (above) verify wave V identification verify repeatability of wave V is wave V too small or wave I too big or both? verify inverting electrode site (s'!laller V/1 amplitude ratio with TIPtrode versus earlobe or m~stoid electrode) 1 # Brainstem dysfunctio . ~,latency !;l·' r/: f1t 'Small wave V/1 f.;· ..,.amplitude ratio Brainstem dysfunction? I 1 c· I !; I t I 1 ?. ,~piked 247 ' .I APPENDIX NORMATIVE DATA 633 ,• 'TABLE A.&. A Simple Guideline for Remembering Important Response Parameters fn Clinical Analysis of the ABR I ,I ' The number five (5) is a critical clue (see bold font). a high click stimulus intensity, such as 85 dB nHl ... ' • ·• • • Wave V lat~ncy is normally about 5.5 ms Wave V amplitude is about 0.5 J.LV (microvolts) Upper end of the adult normal region for the wave 1-V latency interval is 4.50 ms Upper end of the term neonate normal region for the wave 1-V latenty interval is 5.00 ms TABLE A.4. Normative Data for Auditory Brainstem Response (ABR) in 189 Adult Subjects with Mean Age of 48 Years ABR PARAMETER NORMAL RANGE OF LATENCY (MS) Wave 1-111 interval Wave 1-V Interval Males Females lnteraural latency difference for wave V Rate-latency shift for wave V (11/sec to 88/sec) 1.23 to 2.85 3.57 to 4.56 3.42 to 4.56 - 0.59 to 0.42 0.12 to 1.32 Adapted from Lightfoot, G. R. (1992). ABR screening for acoustic neuromata: the role of rateinduced latency shift measurements. British Journal of Audiology, 26, 217-227. TABLE A.S. Nontumor (Normative) Statistics for Auditory Brainstem Response (ABR) Wave Component latency Parameters Used in Differentiation of Cochlear versus Eighth-Nerve Pathology in Adults GROUP ABR LATENCY MEASURE (MS) Absolute I Ill v Normal hearing (N = 786) Cochlear 99%ile Mean Mean 1.65 3.80 5.64 (0.14) (0.18) (0.23) 1.97 4.22 6. 18 1.80 3.98 5.82 (0.23) (0.24) (0.27) 2.15 1.84 3.99 (0.14) (0.14) (0.20) 2.49 2.16 4.45 2.17 1.84 4.02 (0.18) (0.16) (0.24) - 0.02 - 0.03 0.00 (0.08) (0.10) (0.11) 0.21 0.26 0.29 -0.01 - 0.03 - 0.03 . (0.25) (0.23) (0.20) - 0.01 0.00 0.00 (0.10) (0.10) (0.11) 0.25 0.25 0.28 - 0.02 0.01 -0.02 (0.16) (0.14) (0.18) lnterwave 1- 111 111-V 1-V interaural wave I Ill v lnteraural interwave .. I-III 111-V 1- V I Adapted from Joseph, West, Thornton, & Hermann, 1987. 3 BOYS TOWN NATIONAL INSTITUTE INFANT AND PEDIATRIC AUDITORY BRAINSTEM RESPONSE NORMATIVE DATA Table B-1 Boys Town Auditory Brainstem Response Normative Data (N=l120) Measurement parameters (courtesty of Michael P. Gore:a) Stimulus Parameters Type Click Duration 100 usee Rate 13/sec Polarity Rarefaction Intensity 20-80 dB nHL in 20 dB steps Transducer BeyerDT48 Acquistion Parameters Amplification 100,000 Electrodes Cz to ipsilateral mastoid with forehead ground. Filter Settings 100-3000Hz Notch Filter None Filter Slopes 6 dB/octave Analysis Period 10.24 or 15.36 msec Number of 1024; two Sweeps replications. From: Hall, James W., Handbook ofAuditory Evoked Responses Allyn and Bacon, Boston. ABR Normative Data Table B-2. ABR Latency and Amplitude values for 80 dB HL Click Intensity Level in Newborns. Table B-3. ABR Latency and Amplitude Values as a function oflntensity Level in Newborns. Latency ~ msec) CA(N) I v I-III III-V 1-V 33-34 (38) Mean 1.78 7.05 2.86 2.41 5.27 SD 0.30 0.39 0.28 0.26 0.36 35-36 (150) Mean 1.78 7.02 2.84 2.39 5.24 0.26 0.38 0.27 SD 0.25 0.36 37-38 (158) Mean 1.74 6.94 2.80 2.34 5.17 SD 0.21 0.42 0.3 1 0.26 0.40 39-40 (111) Mean 1.72 6.82 2.70 2.38 5.09 SD 0.23 0.38 0.27 0.25 0.36 41-42 (74) Mean 1.69 6.69 2.74 2.24 5.00 SD 0.19 0.29 0.22 0.21 0.30 43-44 (35) Mean 1.65 6.53 2.65 2.21 4.88 SD 0.15 0.32 0.26 0.21 0.3 1 Note: Reported by Gorga et al. (1987). Measurement parameters: stimulus-Click, 0.1 msec, 80 dB Ill.. (110 dB peSPL), 13/sec, monaural, Beyer DT48 earphone; acquisition - filters, 100-3000Hz; amplification, 100,000; sweep, 1,024; analysis time, 15 msec; electrodes, Cz-Mi. CA=conceptional age in weeks; N = number of infants. Wave V latency msec CA(N) 80d8 60dB 40d8 20dB 33-34 (38) Mean 7.05 7.62 8.48 9.72 SD 0.49 0.56 0.39 0.41 35-36(150) 8.42 9.61 Mean 7.02 7.58 0.54 0.67 SD 0.38 0.43 37-38 (1 58) Mean 6.94 7.45 8.29 9.57 0.5 1 0.74 0.42 0.44 SD 39-40(ll IT 8.11 9.36 Mean 6.82 7.30 SD 0.38 0.40 0.49 0.57 41-42 (74) Mean 6.69 7.20 8.08 9.31 SD 0.29 0.29 0.35 0.54 43-44(35) 7.94 9.16 Mean 6.53 7.08 SD 0.32 0.33 0.51 0.53 Note: Reported by Gorga et al. (1987). Measurement parameters: stimulus-click, 0.1 msec, 13/sec, monaural, Beyer DT48 earphone; acquisition- filters, 100-3000 Hz; amplification, 100,000; sweeps, 1,024; analysis time, 15 msec; electrodes, Cz-Mi. CA= conceptional age in weeks; N = number of infants. 3 • 33-34 Weeks AFTER CONCEPTION Intensity (dB HL) Peak I (ms) Peak Ill (ms) Peak V (ms) Inter-peak 1-V Mean crSigma Mean crSigma Mean crSigma Mean crSigma 30 4.17 1.13 6.46 1.03 8.88 0 .97 4 .71 0 .98 40 3.59 0.97 6 .17 0 .63 8.51 0.77 4.92 0.78 50 3.21 0.88 5 .79 0 .64 8.19 0.56 4 .98 0.73 60 3.07 0.69 5.38 0 .84 7.76 0.87 4 .69 0.91 70 2.59 0 .84 5 .22 0 .79 7.49 0.56 4.90 0 .75 80 2 .26 0 .81 5 .01 0.74 7.38 0.72 5.13 0 .67 35-36 Weeks Intensity (dB HL) Peak I (ms) Peak Ill (ms) Peak V (ms) Inter-peak 1-V Mean crSigma Mean crSigma Mean crSigma Mean oSigma 30 4.06 0.95 6.58 0 .82 8.77 0.99 4.72 0 .87 40 3.57 0 .89 6.00 0 .71 8.51 0 .60 4.94 0.73 50 3 .18 0 .51 5.72 0 .84 8.11 0 .56 4.93 0.77 60 2.73 0.71 5.33 0.63 7.68 0.41 4.95 0 .52 70 2 .33 0 .68 4.97 0 .55 7.41 0.61 5.08 0.64 80 2.13 0.69 4.47 0.71 7.19 0.48 5.06 0.56 37-38 Weeks Intensity (dB HL) Peak I (ms) Mean crSigma Peak Ill (ms) Peak V (ms) Inter-peak 1-V Mean crSigma Mean crSigma Mean crSigma 30 3.78 1.04 6.31 0.78 8.39 0 .88 4.61 0.90 40 3.22 0 .78 5 .61 0 .66 7.95 0 .69 4.73 0.71 50 2.94 0.64 5.43 0 .73 7.65 0.72 4 .71 0 .68 60 70 2.47 0 .89 5.06 0.43 7.28 0 .55 4.70 0.71 2.24 0 .67 4.75 0.41 7.17 0.47 4 .93 0 .54 80 2.02 0 .53 4.61 0.47 7.01 0.48 4.99 0.48 39-40 Weeks Intensity (dB HL) Peak I (ms) Peak Ill (ms) Peak V (ms) Inter-peak 1-V Mean oSigma Mean crSigma Mean oSigma Mean crSigma 30 3 .59 0 .81 5 .79 0 .84 8 .03 0 .72 4.44 0 .69 40 3.06 0.87 5.36 0.74 7.65 0 .55 4 .59 0.66 50 60 2.65 2.38 0 .72 0.58 5.01 4.71 0 .59 0 .62 7.31 7.07 0 .53 0.49 4.66 4 .69 0.60 0.51 70 1.94 0 .51 4.57 0.44 6 .83 0.48 4 .89 0.46 80 1.79 0.59 4.26 0 .62 6 .72 0.40 4.93 0.59 SmartEP System Manual 50 s 2 months Peak I (ms) Peak Ill (ms) Peak V (ms) Inter-peak 1-V Mean crSigma Mean crSigma Mean crSigma Mean crSigma 30 ' 40 3.11 0.62 7.58 7.23 0.31 4.47 4.51 0.52 0.41 0.39 0.45 0.48 2.72 5.64 5.18 50 2.35 0.44 4.85 0.37 6.91 0.34 4.56 0.37 60 70 2.14 4.64 0.35 6.69 0.34 4.27 0.41 6.51 0.30 0 .38 4.55 1.81 0.42 0.30 4.70 0.33 80 1.64 0.43 4.18 0.32 6.39 0.29 4 .75 0.36 Intensity (dB HL) 0.46 6 months Peak I (ms) Peak Ill (ms) Peak V (ms) Mean crSigma Mean Mean 30 2.86 0.61 5.08 0.50 40 50 60 2.49 2.28 1.93 0.48 0.41 0.31 4.93 4.75 4.46 0.37 0.37 0.40 70 80 1.79 '1.60 0.32 0.26 4.26 4.10 0.34 0.31 6.50 6.27 Intensity (dB HL) crSigma crSigma Inter-peak 1-V Mean crSigma 7.20 0.44 4.34 0.42 6.86 6.68 6.34 0.33 0.41 0.27 4 .37 4.40 4.41 0.43 0.36 0.30 0.31 0.21 4.71 4.67 0.26 0.28 12 Months Intensity (dB HL) Peak I (ms) Mean crSigma Peak Ill (ms) Mean crSigma 30 40 50 2.90 2.43 2.18 0.44 0.40 0.26 5.11 4.59 4.43 0.51 0.22 0.23 0.18 60 70 1.91 1.81 0.29 0.23 4.01 3.84 80 1.62 0.24 3.79 0 .29 0.32 Peak V (ms) Mean crSigma Inter-peak 1-V Mean crSigma 7.09 6.62 4.19 4.19 0.47 0.37 6.47 0.39 0.36 0.21 4.29 0 .27 6.15 6.14 0.24 0.19 4.24 4.33 0.33 0 .23 5.93 0.17 4.31 0.19 Adult Intensity (dB HL) Peak I (ms) Peak Ill (ms) Peak V (ms) Inter-peak 1-V Mean crSigma Mean crSigma Mean crSigma Mean crSigma 30 40 50 60 2.83 2.46 2.23 1.88 0.36 0.31 0.34 0.27 5.00 4.55 4.49 4.11 0.31 0.26 0.18 0.20 6.69 6.29 6.12 5.81 0.29 0 .27 0.22 0.27 3.86 3.83 3.89 3.93 0.30 0.15 0.24 0.22 70 80 1.75 1.59 0.21 3.86 3.64 0.23 5.67 0.22 5.57 0.15 0.16 3.92 0.17 3.98 0 .25 SmartEP System Manual 0.24 51 ,. . ABR site of lesion protocol Parameters to be lnsoected: 1. 2. 3. 4. 5. 6. 7. 8. Absolute latencies Interpeak latency intervals Interaural latency differences ., Latency-intensity function Stimulus rate change (compare WV at 7.7 cps to WV ~t 57.7 cps) Amplitude ratios (Amp WVI Amp WI) -~ :; Waveform morphology (look for presence of all three {~a~es) Replicability . :.; '.. Enhancement of Wave I ;, • • • • • • ,. . Increase intensity Decrease rate -~ Compare rarefaction and condensation to distinguish CM from neural response (CM present> dB) Use TM or TTM electrode (ECochG) Use horizontal recording montage If no WI use toneburst at frequency equal to the highP.~t frequency where hearing is symmetrical (+/- 10) Norms for Normals at 75dB HL (+/- 2 SDsl (Should reolicate within o.i msl ' 1.6 ms Ill 3.6-3.7 v 5.6 (if wave V is less than or equal to .6ms consider ABR normal) I-III 2 ms {8th nerve to lower BS) 111-V 2 Ms (Extra axial BS) 1-V 4 ms (Intra axial BS)(I-V between the ears should be within .4 ms) V-V within 0.2-0.4 ms (make sure at same intensity) Amplitude Amp V/Amp 1)-1 Rate 7.7 to 5.7 =.5ms (+/- .3 ms) {Increasing from 10/sec to 100/sec shift~ WV b~' 0.5ms) (synchrony and ~ recovery) NHL norms (run normal hearing subjects to determine click threshold, th.e._average will then become OdB nhl '*'Absolute latencies less important than interpeak and interaurallatencies '\. Change in latency with increase or decrease in body temperature=.2ms/degr~ ~elsius away from 98.8 ( Do not need to use correction factors for asymmetrical loss if retrocochlec.r will be huge difference. Absolutes ' may be a little off but the interpeaks must be WNLs or should consider ABNORMAL -kwv slightly later in contra; WIV-V complex more spread apart in contra; no Wave I in contra MS looks retro with prolonged interpeaks and.sometimes amp ratio abnormalities (MRI r/o tumor vs. tissue) • ABR site of lesion protocol Filter ~~[ - .: . 30-3000Hz (If too noisy then switch to ··· 1500Hz) (light_s out) . . .~ ·~~ ;~ ~ • • .rl 100~3CJOOHz or 30- ~ Epoch 0-10 or 0-12 msec for site df lesion Rate Start with 22.7 to find bestw~veform then compare 7.7 & 57.7 (.1 ms change in latency for ever-V 10 cps chtmge in rate) (7.7 to 57.7 expect WV to change by about .·s ms (Sq=/- .3) · (greater than 30 cps increases latency ar1d de'creases amplitude) (31.1/sec and 11.1/sec) Polarity l ' , I .. ; I Adults start with condensation (positiv~1b'asilar membrane down first; slightly better wave V) (raref_pction negative pulse, earlier and larger wave· I)· BC always use alternating polarity ~ Stimulus 100 uv Click Intensity Start at 75dbnhl, if poor waveform theriBSdB, if still bad try different polarity, if still ba~ try 95 dB inJensity or slow rate to 7.7 cps. (Very high intensity ~ay invoke the acoustic reflex.) Artifact Rejection 10 uv (up to 25 uv) Sweeps 2000 ; I .. . J Protocol ABR Site of Lesion: -t • • • • • • • ( • • • • • Start with poorer ear at 85dB nHL wit~ condensation clic~ @27.7 cps If WI and WV responses aren't clear change to rarefaction Increase to 95dB Change back to condensation at 95dB, then 100 dB Then rarefaction at 100 dB Slow rate to 7.7 cps _ ) Try TB at last Hz where audio symmetrical within 10 dB (if WV latencies~of TBs are comparable the patient is ok) 1"t3~ ~ ~ Replicate at 27.7 cps (should be within·o.l ms) Change to 7.7 cps and replicate Change to 57.7 (or 77.7 cps) look at WV SWITCH to other ear and start at 57.7 cps and replicate ,. , Then 7. 7 cps and replicate J ADULT NORMS ~ < Y Wave I II III IV v VI ,_ • -- ~ • -- •~ • A • ~ Absolute Latencies (msec) Mean SD Mean+3 SD 1.7 0.15 2.2 2.8 0.17 3.3 3.9 0.19 4.5 0.24 5.1 5.8 5.7 0.25 6.5 7.3 0.29 8.2 - -~ Waves I-III I-V III-IV III-V IV-V V-VI ~ • • ..., lntenvave Latencies Mean+ 3 SD Mean SD 2.1 2.6 0.15 4.0 4.7 0.23 1.2 0.16 1.7 2.4 1.9 0.18 1.3 0.7 0.19 0.25 1.5 2.3 - • ~ --«- v- -- - - Interear lnten,·aw Differences Mean+ 3 SD Mean SD 0.37 (0.4) 0.10 0.09 0.43 (0.5) 0.13 0.10 0.54 (0.6) 0.14 0.12 0.43 0.10 0.11 0.57 (0.8) 0.14 0.15 0.79 (0.8) 0.22 0.19 Normal values for BAEPs obtained from 50 normal subjects (15 to 51 years old, mixed gender) at 10 clicks/sec. Square wave duration was 0.1 msec, click intensity was 60 dB SL, constant polarity. Latencies were measured to the wave peak; where a peak was not well defined, a midpoint of the wave was estimated. When waves IV and V were fused into a single peak, the latency was taken to the point of final inflection before the negative limb of wave V, and this was recorded as wave V only. If either wave appeared as a distinct step on the other, this step was taken as the wave peak. From: Chiappa, Keith H., M.D., Evoked Potentials in Clinical Medicine Second Edition, Raven Press, New York. ABR Nonnative Data 2 Torie -Burst ABR Settings Auditory Brainstem Responses are usually acquired using click stimulation. However, click stimulation distributes the energy of the sound over the entire frequency spectrum and provides no frequency specific information. This specific information can be used to help with hearing aid fitting and other types of diagnosis. Tone Bursts. Exact Blackman. 500 Hz: 8000us 1000 Hz: 5000 us or 4000 us 2000 Hz: 5000 us or 4000 us 4000 Hz: 5000 us or 2000 us 8000 Hz: 5000 us or 1000 us. None. Masking: 27'. 7jsec or 39.1 ;sec. Slower Rate: rates are used to enhance wave I. Rate should not be a multiple of the line current (e.g. 60 Hz). Condensation for 500Hz andjor Polarity: Alternating for all frequencies. Transducers: Insert Earphones. Intensity: 80 to 95 dB HL for Neurodiagnosis. 90 dB HL down to 0 dB HL for Threshold search. 30 - 1500 Hz (for Adult ABA Filters: and infant ABA). Notch Filter: OFF. ON if there is excessive electrical line noise present. Amplification: 1OOx Analysis Time 25.6 milliseconds for 500 Hz Window: and 1000 Hz; 12.8 milliseconds for all others. 2000 - 2048. Sweeps: Electrode Ipsilateral or Contralateral Array. Montage: Notice that the latency of the response increases as the intensity of stimulation is decreased. Stimulus: Envelope: Duration: The following graph shows the relationship of latency with respect to frequency. Note that lower frequency tones have a higher latency value than higher frequency tones, reason why it is recommended to use a wider time window at lower frequencies. Tone Burst Analysis A tone burst series used for threshold detection is displayed in the following figure. The series shown is for a 500 Hz tone presented using the parameters outlined in the previous table. INTEWGENT HEARING SYSTEMS 1-800-IHSYSTEMS- www.ihsys.com SNSEP010a Rev: 54066 lo