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Auditory Electrophysiology in Audiology Today: Current, Best, and Future Practices Canadian Academy

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Title: Auditory Electrophysiology in Audiology Today: Current, Best, and Future Practices Canadian Academy


1
Auditory Electrophysiology in Audiology Today
Current, Best, and Future Practices Canadian
Academy of Audiology 2008 Conference
  • James W. Hall III, Ph.D.
  • Clinical Professor and Associate Chair
  • Department of Communicative Disorders
  • College of Public Health Health Professions
  • University of Florida
  • Gainesville, Florida 32610-0174
  • Jwhall3_at_phhp.ufl.edu
  • and
  • Extraordinary Professor
  • University of Pretoria
  • South Africa

2
My Canadian Ancestry Grandmother Blanche McLean
Wood (and my first otoscopic examination of Dr.
James W. Hall, Sr.)
3
My Canadian Ancestry Hometown of grandmother
Blanche McLean Wood Douglastown, Northumberland,
New Brunswick
4
My Canadian Ancestry Miramichi River New
Brunswick, Canada
5
Auditory Electrophysiology in Audiology Today
Best and Future Practices
  • Electrocochleography (ECochG) in the diagnosis of
    auditory neuropathy
  • Maximizing efficiency and minimizing test time in
    frequency-specific ABR estimation of auditory
    thresholds in infants
  • Techniques and technology for diagnostic ABR
    assessment without sedation or anesthesia
  • Auditory steady state evoked response (ASSR) in
    pediatric audiologic assessment Pros, cons
    questions
  • Brainstem and cortical auditory evoked responses
    in auditory processing disorders (APD)

6
Ernest Glen Wever … Discoverer of ECochG (October
16, 1902 September 4, 1991)
7
Original Description of Electrocochleography
(ECochG)
  • Wever EG and Bray CW. 1930. Action currents in
    the auditory nerve in response to acoustic
    stimulation. Proceedings of the National Acad of
    Science (USA) 16 344-350.
  • Wever EG and Bray CW. 1930. Auditory nerve
    impulses. Science 71 215.

8
ELECTROCOCHLEOGRAPHY Celebrating the 75th
Anniversary!
Ruben (CM AP clinically)
Coats, Eggermont, Gibson (Dx of MD)
Tasaki (AP in human)
Yoshie, Portmann (TT CM AP)
Davis (SP)
Coats (EAC)
Fromm et al (CM in human)
Various (Auditory Neuropathy)
Hall (I/O)
Wever Bray (CM in cat)
1930
1935
1950
1954
1960
1967
1974
1990
1996
Time in Years
9
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10
ELECTROCOCHLEOGRAPHY Generators
  • Cochlear microphonic (CM)
  • outer hair cells
  • receptor potentials
  • Summating potential (SP)
  • inner hair cells (gt 50)
  • outer hair cells
  • organ of Corti
  • Action potential (AP)
  • afferent fibers in distal 8th cranial nerve
  • spiral ganglion

11
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12
ECochG TEST PROTOCOL (1)
  • Stimulus Parameters
  • Type clicks
  • Duration 0.1 msec
  • Rate 7.1/sec or slower as necessary
  • Polarity alternating (for AP) or rarefaction
    (for CM)
  • Intensity maximum or lower
  • Transducer Insert
  • Masking never needed (response is ipsilateral)

13
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14
ECochG TEST PROTOCOL (2)
  • Acquisition Parameters
  • Amplification 75,000 or less
  • Analysis time 5 or 10 msec
  • Sweeps 500 or less
  • Filters 10 to 1500 Hz
  • Notch filter never
  • Electrodes
  • option 1 Fz to tympanic membrane
  • option 2 Fz to tiptrode
  • option 3 Fz to transtympanic needle

15
ECochG Measurement Principle The closer to the
cochlea, the better
16
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17
ELECTROCOCHLEOGRAPHY (ECochG) AP (ABR wave I)
amplitude as a function of electrode site
3.5 3.0 2.5 2.0 1.5 1.0 0.5
Amplitude in mvolts
Mastoid Earlobe Earcanal TM
Promontory Electrode Site
18
TIPtrode Part transducer and part electrode
19
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20
AUDITORY NEUROPATHY Terminology
  • Auditory neuropathy, or AN (coined in 1995 by
    neurologist Arnold Starr)
  • Only an auditory disorder, i.e., type II AN
    (Starr et al, 1996)
  • Poly-neuropathy and patients who later develop
    additional peripheral neuropathies, i.e., type I
    AN (Starr et al, 1996)
  • Really neural or inner hair cell (sensopathy)
  • Auditory dys-synchrony (Chuck Berlin)

21
AUDITORY NEUROPATHY Proper Terminology (Senso
Stricto) According to Isabelle Rapin and Judy
Gravel (2003)
  • We object on scientific grounds to the use of
    the term auditory neuropathy when the main site
    of pathology is in the brain stem or more
    centrally in the auditory pathway. Loose use of
    the term auditory neuropathy is confusing,
    likely to be anatomically incorrect, and
    engenders imprecision rather than emphasizing the
    strong need for comprehensive behavioral,
    electrophysiological, and pathologic
    investigation. … Therefore, we urge that the term
    auditory neuropathy senso stricto be reserved for
    demonstrable involvement of the spiral ganglion
    cells or their processes, and not be used for
    pathologies of uncertain or mixed locations (p.
    724).

22
AUDITORY NEUROPATHY Early literature (1)
  • Lutman, Mason, Sheppard Gibbin. Audiology 28
    1989
  • Prieve , Gorga Neely. JSHD 34 1991
  • Baldwin Watkin. J Laryngol Otol 106 1992
  • Katona et al. IJPORL 26 1993
  • Konradsson. Audiology 35 1996
  • Laccourreye et al. Annals of ORL 105 1996
  • Starr, Picton, Sininger, Hood Berlin. Brain
    119 1996
  • Stein et al. Seminars in Hearing 17 1996
  • Watkin. Arch Dis Child 74 1996

23
AUDITORY NEUROPATHY Early literature (2)
  • Deltenre et al. EEG Clin Neurophys 104 1997
  • Parker , Webb Stevens, Brit Soc Audiology,1997
  • Psarommatis et al. IJPORL 39 1997
  • Berlin et al. Ear Hearing 19 1998
  • Hall et al. Seminars in Hearing 19 1998
  • Starr et al. Ear Hearing 19 1998
  • Wood, Mason, Farnsworth, Davis, Curnock Lutman.
    BJA 32 1998
  • Miyamoto et al. Laryngoscope 109 1999
  • Rance et al. Ear Hearing 20 1999
  • Many articles since 1999
  • Medline search (www.nlm.nih.gov) with key words
    auditory neuropathy on September 9, 2008 500
    publications

24
AUDITORY NEUROPATHY Very recent literature
(12 of 14 latest articles in by Chinese authors!)
  • Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi.
    2008 May43(5)347-50. Electrophysiological
    findings for 106 cases with auditory neuropathy
    Article in Chinese
  • Wang JB, Duan JD, Chen HH, Jin J, Li QT,
    Huang X, Kong WJ.
  • Department of Otorhinolaryngology, Union
    Hospital, Huazhong University of Science and
    Technology, Wuhan 430022 ,China.
    Wangjb696_at_163.com
  • OBJECTIVE To analyses the clinical
    characteristics and electrophysiological finding
    of 106 patients with auditory neuropathy (AN).
    Investigate the differential curve type of pure
    tone audiogram and the abnormal ABR. METHODS
    Review the history of patients, pure tone
    audiometry, middle ear acoustic reflexes,
    auditory brainstem response, distortion product
    otoacoustic emission and radiologic imaging
    studies of the brain of 106 patients with AN
    during December 2001 to May 2007 in retrospect.
    RESULTS The 106 patients with AN were of both
    genders. The age were between 11-37 years old,
    and the average age was 17.5 years old. The most
    patients were adolescences (70.8). Twelve cases
    of the 106 patients had evidence of other
    peripheral neuropathy in addition to hearing
    loss. Another 94 patients were idiopathic
    origins. The pure tone audiogram showed a minimal
    to moderate sensorineural hearing loss at low
    frequencies 0.5 kHz and 0.25 kHz in 209 ears
    (98.6). The average hearing threshold (WHO 1997)
    in 23.2 of disordered ears at less than 25 dB in
    the "normal" range. Auditory brainstem response
    could not be recorded in 124 ears (58.5) at
    maximum stimulus. The other 88 ears showed 1 or 2
    wave, but the wave were small. There were 23
    patients which one side ear ABR was 1 or 2 small
    waves presented, but the contralateral side were
    all waves absent. In 3 cases of AN with other
    peripheral neuropathy which ABR were both ears 1
    or 2 small wave ear recorded. However, 1 patient
    in our sample could not be detected distortion
    product otoacoustic emission at 3-6 kHz (left
    ear) and 5-6 kHz (right ear). CONCLUSIONS AN was
    not rare in adolescences. The average hearing
    threshold for AN should be discussed.

25
AUDITORY NEUROPATHY Refining diagnosis of
site of lesion
  • McMahon, Patuzzi, Gibson Sanli. (2008)
    Frequency-specific electrocochleography indicates
    that presynaptic and postsynaptic mechanisms of
    auditory neuropathy exist. Ear Hearing, 29,
    314-325.
  • 14 subjects (7 male and 7 female) with AN versus
    2 normal subjects
  • AN diagnosed between 3 and 24 months of age
  • Diagnosis based on large CM potentials and
    absence of ABR (incl. wave I)
  • Genetic etiology for 6 subjects
  • Severe to profound audiometric thresholds for all
    subjects
  • All subjects received cochlear implants
  • Purpose of study was to better define physiology
    mechanisms of AN to guide management (including
    cochlear implantation)
  • ECochG recorded with
  • Non-inverting (active) electrode near round
    window golf club electrode (via myringotomy)
  • Inverting electrode on ipsilateral earlobe
  • ECochG in AN consistent with
  • Pre-synaptic mechanism (abnormal SP) good EABR
    and CI benefit
  • Post-synaptic mechanism (normal SP dentritic
    potential) but no AP poor or absent EABR and
    poor CI benefit

26
AUDITORY NEUROPATHY Examples of ECochG
Components (McMahon et al, 2008)
CM
Condensation Rarefaction
Alternating
N2
SP
N1
DP (dentritic potential)
Analysis Time
10 ms
27
Auditory Neuropathy Sites of Lesions and
Patterns of Auditory Findings McMahon et al.
(2008). Frequency-specific ECochG indicates that
presynaptic and postsynaptic mechanisms of
auditory neuropathy exist. Ear Hearing 29
314-325.
  • Auditory Findings (? normal ? abnormal)
  • Site of Lesion OAEs ECochG
    ABR Acoustic Reflexes EABR
  • CM SP DP CAP
  • Inner hair cells ? ? ? ?
    ? ? ? ?
  • Primary afferent synapse ? ? ?
    ? ? ? ? ?
  • Auditory nerve ? ? ? ?
    ? ? ? ?
  • Auditory brainstem ? ? ? ?
    ? ? ? ?
  • DP dentritic potential (broad negative wave)

28
AUDITORY NEUROPATHY Refining diagnosis of
site of lesion (2)
  • Santarelli, Starr, Michalewski Arlsan (2008).
    Neural and receptor cochlear potentials obtained
    by transtympanic electrocochleography in auditory
    neuropathy. Clinical Neurophysiology, 119,
    1028-1041.
  • 8 subjects (with AN versus 16 normal subjects
  • AN subjects between 5 and 48 years of age
  • Diagnosis based on presence of DPOAEs and absence
    of ABR (incl. wave I)
  • Enlarged CM in AN patients (Starr et al, 2001
    Santarelli Arslan, 2002)
  • Etiology
  • Hereditary (3)
  • Immunolological (3)
  • Degenerative (1)
  • Congenital (1)
  • ECochG measures included
  • CM
  • SP
  • AP
  • Adaptation of AP determined by AP elicited by a
    first click versus AP elicted by a train of 10
    rapid clicks (2.9 ms ISI)

29
AUDITORY NEUROPATHY Medical diagnoses (1)
  • Perinatal Diseases
  • Hyperbilirubinemia
  • Hypoxic insults
  • Ischemic insults
  • Prematurity 
  • Neurological Disorders
  • Demyelinating diseases
  • Hydrocephalus
  • Immune disorders, e.g., Guillain-Barre sydrome
  • Inflammatory neuropathies
  • Severe developmental delay

30
AUDITORY NEUROPATHY Medical diagnoses (2)
  • Neuro-metabolic diseases
  •  Genetic and Hereditary Etiologies
  • Family history
  • Connexin mutations, e.g., GJB3 (D66del)
  • Otoferlin (OTOF) gene
  • Non-syndromic recessive auditory neuropathy
  • Hereditary motor sensory neuropathies (HMSN),
    e.g., Charcot-Marie-Tooth syndrome
  • Lebers hereditary optic neuropathy
  • Waardenburgs syndrome
  • Neurogenerative diseases, e.g., Friedreichs
    ataxia
  • Mitochondrial disorders, e.g., mitochondrial
    enzymatic defect

31
ELECTROCOCHLEOGRAPHY (ECochG) Clinical
Applications
  • Diagnosis of auditory neuropathy
  • TIPtrode (pediatric) or earlobe electrode
  • Detection of ECochG components
  • CM single polarity signals (rarefaction and
    condensation)
  • SP alternating polarity (slow and fast rate)
  • AP alternating polarity (slow and fast rate)
  • Rationale
  • detection of CM confirms outer hair cell function
  • detection of SP confirms inner hair cell function
  • detection of AP confirms distal 8th cranial nerve
    function

32
AUDITORY NEUROPATHY Anatomy and Physiology
Action potential (AP)
Summating potential (SP)
Cochlear microphonic (CM)
33
AUDITORY NEUROPATHY Detection
Otoacoustic Emissions
Absent?
ABR
Present?
Middle Ear Disorder?
Normal ME?
No response, wave I only or delayed I-V?
ABR threshold elevated but I-V WNL?
Diagnostic Audiology
IHC dysfunction?
Medical Mgt
Audiologic Mgt
Auditory Neuropathy
34
AUDITORY NEUROPATHY Possible Medical diagnoses
  • hyperbilirubinemia (probably 1)
  • neurodegenerative diseases, e.g., Friedreichs
    ataxia
  • neurometabolic diseases
  • demyelinating diseases
  • hereditary motor sensory neuropathies, e.g.,
    Charcot-Marie-Tooth syndrome
  • inflammatory neuropathies
  • hydrocephalus
  • severe developmental delay
  • ischemic/hypoxic neuropathy
  • cerebral palsy
  • unknown etiology

35
Auditory Brainstem Response Findings in Auditory
Neuropathy (cochlear microphonic)
36
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37
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38
AUDITORY NEUROPATHY Audiologic Management
  • Close monitoring every three months until
    behavioral audiometry is complete consider
    videotaping all observations)
  • Monitor OAEs
  • Referral to other disciplines (pediatric
    neurology, developmental pediatrics, speech
    pathology)
  • Hearing aids (delay until hearing loss by
    audiometry)
  • Assistive listening devices
  • Alternative communication strategies
  • Cued speech
  • Visual emphasis aural approaches
  • Signing options

39
Auditory Electrophysiology in Audiology Today
Best and Future Practices
  • Electrocochleography (ECochG) in the diagnosis of
    auditory neuropathy
  • Maximizing efficiency and minimizing test time in
    frequency-specific ABR estimation of auditory
    thresholds in infants
  • Techniques and technology for diagnostic ABR
    assessment without sedation or anesthesia
  • Auditory steady state evoked response (ASSR) in
    pediatric audiologic assessment Pros, cons
    questions
  • Brainstem and cortical auditory evoked responses
    in auditory processing disorders (APD)

40
Limitation of Click-Evoked ABR Lack of
Frequency-Specificity
Normal click ABR Abnormal or no click ABR
41
Estimation of Frequency-Specific Auditory
Thresholds with Tone Burst ABRs Initial Data
Points for DSL
42
Importance of Latency Calculation in ABR
Analysis Differentiation of Normal versus
Abnormal
V
I
III

Both normal ABRs?
15 ms
Stimulus
Analysis Time
43
AUDITORY BRAINSTEM RESPONSE (ABR) Wave V
Latency-Intensity Function
Abnormal ABR (hearing loss in 2-4 K Hz region)
8
Wave V Latency in msec
6
4
0
100
20
40
60
80
Click Intensity in dB nHL
44
Click versus Tone Burst ABRs
I
III
V
click
I
III
V
50
1000 Hz
V
500 Hz
0
15 msec
Stimulus
Analysis Time
45
Frequency-Specific ABR Test Protocol Stimulus
Parameters
  • Parameter Selection Rationale
  • Transducer ER-3A inserts Numerous infant
    advantages
  • Type tone bursts Available on all systems
  • Frequencies 1, .5, 4, 2 K Hz Sequence varies
    clinically
  • Duration 2-0-2 cycles Abrupt frequencies
  • 0 plateau lt spectral splatter

46
FREQUENCY-SPECIFIC ABRs Effect of Tone Burst
Onset Window (Ramp)
47
Frequency-Specific ABR Test Protocol Stimulus
Parameters
  • Parameter Selection Rationale
  • Polarity Alternating Minimize stimulus
    artifact
  • single polarity stimuli recommended
    by some experts (e.g., Hood)
  • Rate 33.1/sec Rapid data collection with
    adequate response integrity
  • with longer analysis time
  • Intensity dB nHL RE adult behavioral data

48
Frequency-Specific ABR Test Protocol Acquisition
Parameters
Parameter Selection Rationale Artifact
reject On Minimize muscle artifact Analysis
time 20 ms Encompass delayed wave
Vs and SN10 after wave V Sweeps 100 to gt
2000 Whatever is needed for SNR for poor
morphology ABRs Reliability 2 or 3 runs If it
doesnt replicate, you must investigate
49
Frequency-Specific ABR Test Protocol Acquisition
Parameters
  • Parameter Selection Rationale
  • Electrode type Disc ear-clip Disposable
    electrodes with infants Vivosonic
    Integrity uses Amplitrode design electrode
  • Electrode location Fz - Nape or Ai Optimal
    infant response
  • Fpz ground Ai good for BC stimulus
  • Filter settings 30 - 3000 Hz Encompass infant
    spectrum
  • no notch filter of ABR (more low frequency)
  • Vivosonic Integrity uses Kalman
    filtering
  • Artifact reject On Minimize muscle artifact
  • doesnt apply with Vivosonic Integrity
    device

50
FREQUENCY-SPECIFIC AUDITORY BRAINSTEM RESPONSE
(ABR) Relation to Audiogram (Oates Stapells,
1998)
51
(No Transcript)
52
Electrophysiologic Estimation of the Audiogram
8K
6K
4K
3K
2K
1K
.50
8K
6K
4K
3K
2K
1K
.50
dB HL
20 40 60 80 100
PT ABR ASSR
Right Ear Frequency in Hz
Left Ear Frequency in Hz
53
Examples of ABR Elicited with Tone Burst
Stimuli Click ABR (1.5 year child with language
delay parents from Thailand)
54
Examples of ABR Elicited with Tone Burst
Stimuli 4000 Hz stimulus
55
Examples of ABR Elicited with Tone Burst
Stimuli 1000 Hz stimulus
56
Examples of ABR Elicited with Tone Burst
Stimuli 500 Hz stimulus
57
Simple Techniques for Saving Valuable Time in
Frequency-Specific Estimation of an Audiogram
with Tone Burst ABRs (test time of 30 minutes or
less)
  • Be prepared to begin ABR as soon as the child is
    asleep
  • Equipment is set up with patient information
  • Electrodes are handy with electrode gel or paste
  • Tape is cut
  • Insert earphones are ready with proper size tips
  • Record ABR with measurement conditions that
    optimize the SNR, I.e, maximize the signal (ABR)
    and minimize the noise (all other electrical
    activity)
  • Sleeping, sedated, or anesthetized child
  • Low and balanced electrode impedance
  • Little or no electrical artifact
  • Deep fitting insert earphone to minimize ambient
    acoustic noise
  • Use a stimulus presentation rate of about
    37.7/sec to speed up data collection
  • Immediately trouble-shoot if the ABR findings are
    different from what you expect

58
Simple Techniques for Saving Valuable Time in
Frequency-Specific Estimation of an Audiogram
with Tone Burst ABRs (test time of 30 minutes or
less)
  • Think ahead to the next step in the assessment
    while signal averaging … dont do your thinking
    between periods of data collection
  • At high stimulus intensities
  • Discontinue signal averaging as soon as a clear
    response is detected (lt 500 stimuli or sweeps)
  • Immediately replicate with even fewer averages
  • Calculate latencies and amplitudes while also
    collecting data at the next intensity level
  • Drop the stimulus intensity level as quickly as
    possible to near threshold (e.g., from 80 dB nHL
    down to 40 dB nHL if the ABR has a wave I and
    wave V)
  • After hearing thresholds are estimated with click
    stimuli, begin presenting subsequent tone burst
    stimuli at intensity levels 20 to 30 dB above
    anticipated ABR threshold
  • Dont replicate flat ABR tracings (when you
    have nothing you have nothing to repeat)

59
Auditory Electrophysiology in Audiology Today
Best and Future Practices
  • Electrocochleography (ECochG) in the diagnosis of
    auditory neuropathy
  • Maximizing efficiency and minimizing test time in
    frequency-specific ABR estimation of auditory
    thresholds in infants
  • Techniques and technology for diagnostic ABR
    assessment without sedation or anesthesia
  • Auditory steady state evoked response (ASSR) in
    pediatric audiologic assessment Pros, cons
    questions
  • Brainstem and cortical auditory evoked responses
    in auditory processing disorders (APD)

60
American Academy of Pediatrics Guidelines for
Conscious Sedation (WWW.AAP.org/policy)
  • Pediatrics 89, 1992, p 1110-1115
  • Guidelines for Monitoring and Management of
    Pediatric Patients During and After Sedation for
    Diagnostic and Therapeutic Procedures
  • Pediatrics 110, 2002, pp 836-838
  • Guidelines for Monitoring and Management of
    Pediatric Patients During and After Sedation for
    Diagnostic and Therapeutic Procedures Addendum

61
ABR in the Clinic with Conscious Sedation (e.g.,
chloral hydrate) No longer in favor among
anesthesiologists
62
ABR in the Operating Room with Light
Anesthesia (e.g., propofol)
63
SEDATION OPTIONS Clinic versus Operating Room
  • Setting Advantages Disadvantages
  • Clinic
  • ? inexpensive ? limited sedation options
  • ? near or in audiology clinic ? limited
    medical support
  • ? scheduling ease ? increased liability
  • ? uncertain success/gt time
  • ? discouraged by anesthesiologists
  • O.R. ? ENT services ? more expensive
  • ? ideal patient state ? remote location
  • ? controlled sedation ? noisier environment
  • ? limited liability ? complicated scheduling

64
UNSEDATED PEDIATRIC ABR Measurement Techniques
  • Non-medical techniques
  • Sleep deprivation
  • Record ABR immediately after feeding
  • Bean bag bed to minimize movement
  • Benedryl (with pediatrician approval)
  • Melatonin
  • Schmidt et al. Melatonin is a useful alternative
    to sedation in children undergoing brainstem
    audiometry with an age dependent success rate A
    field report of 250 investigations.
    Neuropediatrics 38 2-4, 2007.

65
UNSEDATED PEDIATRIC ABR Measurement Techniques
(2)
66
UNSEDATED PEDIATRIC ABR Measurement Techniques
(3)
  • Melatonin
  • Hormone naturally produced by pineal gland (small
    gland in center of the brain)
  • Controls circadian rhythms
  • Inhibited by light
  • Exposure at night to incandescent light for 39
    minutes reduces melatonin by 50)
  • Chronic reduction in melatonin linked to cancer
    risk
  • Enhanced by darkness
  • Strong antioxidant activity
  • Exogenous melatonin (synthetic, e.g., tablets)
    causes rapid sleep induction without sedation
  • Peak serum concentration reached in about 60
    minutes
  • Concentration declines within 4 hours

67
UNSEDATED PEDIATRIC ABR Measurement Techniques
(4)
  • Selected publications on use of melatonin to
    induce sleep in medicine
  • Brzezinski A. (1997) Melatonin in humans. N Engl
    J Med, 336, 186-195.
  • Dodge NN Wilson GA. (2001). Melatonin for
    treatment of sleep disorders in children with
    developmental disabilities. J Child Neurol, 16,
    581-584.
  • Johnson et al. (2002). The use of melatonin as an
    alternative to sedation in uncooperative children
    undergoing an MRI examination. Clin Radiol, 57,
    502-506.
  • Milstein V et al. (1998). Melatonin for sleep
    EEG. Clin Electroencephal, 29, 49-53.
  • Seabra et al. (2000). Randomized, double-blind
    clinical trial, controlled with placebo, of the
    toxicology of chronic melatonin treatment. J
    Pineal Res, 29, 193-200.
  • Wassmer E et al. (2001). Melatonin is useful for
    recording sleep EEGs a prospective audit of
    outcome. Dev Med Child Neurol, 43, 735-738.

68
(No Transcript)
69
UNSEDATED PEDIATRIC ABR Measurement Technology
  • Vivosonic Integrity auditory evoked response
    device
  • Toronto based company (Dr. Yuri Sokolov,
    President)
  • Blue tooth technology
  • To limit cables and wires
  • Reduceantennae effect of conventional electrode
    leads
  • Eliminate line noise
  • Permit distance from patient and test equipment

70
UNSEDATED PEDIATRIC ABR Measurement Technology
  • AmplitrodeTM in situ amplifier designed to
  • Filter before amplification
  • Optimize gain
  • Reduce electrode lead length
  • Minimize electrical artifact from multiple
    sources
  • Amplify signal but not noise

71
UNSEDATED PEDIATRIC ABR Measurement Technology
  • Kalman weighted averaging
  • Estimates noise in each raw response
  • Weights window based on inverse of noise estimate
  • No signal is discarded
  • Noisy signals contribute less

Rudolph Kalman, PhD
72
Vivosonic Integrity ABR System Technology for
Un-Sedated Infant ABR Measurement Follow up ABR
assessment with 6 month old infant
73
Vivosonic Integrity ABR System Technology for
Un-sedated Infant ABR Measurement Left ear ABR of
4 year old boy with cerebral palsy
74
Vivosonic Integrity ABR System Technology for
Un-sedated Infant ABR Measurement Right ear ABR
of 4 year old boy with cerebral palsy
75
Auditory Electrophysiology in Audiology Today
Best and Future Practices
  • Electrocochleography (ECochG) in the diagnosis of
    auditory neuropathy
  • Strategies for frequency-specific ABR estimation
    of auditory thresholds in infants (Greg Ollick)
  • Instrumentation for diagnostic assessment of
    children without sedation or anesthesia (Greg
    Ollick)
  • Update on the pros and cons of auditory steady
    state evoked response (ASSR) in pediatric
    audiologic assessment
  • Recent research on auditory evoked responses in
    auditory processing disorders

76
Auditory Electrophysiology in Audiology Today
Best and Future Practices
  • Electrocochleography (ECochG) in the diagnosis of
    auditory neuropathy
  • Strategies for frequency-specific ABR estimation
    of auditory thresholds in infants
  • Instrumentation for diagnostic assessment of
    children without sedation or anesthesia
  • Update on the pros and cons of auditory steady
    state evoked response (ASSR) in pediatric
    audiologic assessment
  • Recent research on auditory evoked responses in
    auditory processing disorders

77
Limitation of Tone Burst ABR in
Severe-to-Profound Hearing Loss
8K
6K
4K
3K
2K
1K
.50
8K
6K
4K
3K
2K
1K
.50
dB HL
20 40 60 80 100
No ABR gt 80 dB HL
No ASSR gt 120 dB HL
AC BC
Frequency in Hz
Frequency in Hz
78
Diagnosis of Hearing Loss Protocol for
Confirmation of Hearing Loss in Infants and
Toddlers (0 to 6 months) Year 2007 JCIH Position
Statement
  • Child and family history
  • Otoacoustic emissions
  • ABR during initial evaluation to confirm type,
    degree configuration of hearing loss
  • Acoustic immittance measures (including acoustic
    reflexes)
  • Supplemental procedures (insufficient evidence to
    use of procedures as sole measure of
    auditory status in newborn and infant
    populations)
  • Auditory steady state response (ASSR)
  • Acoustic middle ear reflexes for infants lt 4
    months
  • Broad band reflectance
  • Behavioral response audiometry (if feasible)
  • Visual reinforcement audiometry or
  • Conditioned play audiometry
  • Speech detection and recognition
  • Parental report of auditory visual behaviors
  • Screening of infants communication milestones

79
AUDITORY STEADY STATE RESPONSE (ASSR) Confusing
Terminology
  • Amplitude-modulation-following response (AMFR)
  • Envelope -following response (EFR)
  • Frequency-following response (FFR)
  • Steady state evoked response (SSER)
  • Steady state evoked potential (SSEP)
  • 40 Hz response
  • Auditory steady state response (ASSR)

80
ASSR General Principles
  • An electrophysiologic response, similar to ABR.
  • Instrumentation includes
  • Insert earphones
  • Surface electrodes
  • Averaging computer
  • Stimuli are pure tones (frequency specific,
    steady state signals) activating cochlea and CNS
  • ASSR is generated by rapid modulation of
    carrier pure tone amplitude (AM) or frequency
    (FM).
  • Signal intensity can be as high as 120 dB HL
  • ASSR phase or frequency is detected automatically
    (vs. visual detection)

81
Auditory Steady State Response (ASSR) Clinical
Devices
  • GSI VIASYS
  • Audera
  • Descendant of Melbourne Australia system (Field
    Rickards, Gary Rance, Barbara Cone-Wesson, et al)
  • Bio-Logic Systems Inc.
  • MASTER
  • Descendent of Canadian system (Terry Picton et
    al)
  • ICS
  • HIS
  • Others?

82
ASSR 2000 Hz tone modulated at rate of 100 Hz
83
ASSR Response imbedded within EEG
84
ASSR Graphic display in vector plot of EEG
samples at modulation frequency
B
  • Vector length (c) magnitude of activity
  • Vector angle (a) phase lag between stimulus MF
    and EEG at MF

c
b
a
C
A
85
ASSR (Audera) Significant phase coherence
86
ASSR (Audera) No Response Condition
87
ASSR (Audera) Test trials by frequencty
88
ASSR (Audera) Estimated Audiogram
89
(No Transcript)
90
500
1000
2000
4000
EEG ASSR
91
The Auditory Steady-State Response A New Book
and gt 400 Medline Hits (www.nlm.nih.gov)
92
ASSR, ABR, and Pure Tone Audiometry Asking the
clinically relevant question
  • Not
  • Which frequency-specific electrophysiologic
  • technique is best … tone burst ABR or ASSR?
  • But
  • How does the ASSR technique complement
  • click and tone burst ABR techniques in the
  • infant test battery?

93
ABR (Click and Tone Burst) versus ASSR Clinical
Application
  • Advantages Disadvantages
  • ABR w Estimates normal w Cant estimate
    profound HL
  • hearing thresholds w Skilled analysis
    required
  • w Ear-specific BC findings w Limited BC
    intensity levels
  • w Diagnosis of AN
  • ASSR w Estimates severe-to- w No ear-specific
    BC findings
  • profound HL w Requires sleep or
    sedation
  • w?Possible artifactual response

94
ASSR Is it possible to mistake an artifact for
a response?
  • Literature Air conduction
  • Gorga et al, 2004 found apparent ASSRs for
    stimulus intensity levels gt 100 dB HL in patients
    with cochlear implants (disenabled)
  • Picton John, 2004
  • Small Stapells, 2004
  • Literature Bone conduction
  • Dimitrijevic et al, 2002
  • Small Stapells, 2005
  • Explanations and conclusions
  • Aliasing in measurement when signal is sampled at
    a rate less than twice its frequency
  • Problem was apparently limited to research or
    early clinical version of MASTER system
  • Based on clinical experience, it is clearly
    possible to perform ASSR measurement at intensity
    levels up to 120 dB HL without detection of a
    response (with Audera device)

95
Hearing Status in Infants Undergoing Sedated
Frequency Specific ABR (Nicolet Spirit) and ASSR
(GSI Audera) N 74
  • Normal hearing sensitivity 54 (40)
  • Hearing loss 46 (34)
  • Conductive 26 (9)
  • Sensory 44 (15)
  • w mild 6/15
  • w moderate 2/15
  • w severe 5/15
  • w profound 2/15
  • Mixed 9 (3)
  • Neural 6 (1)
  • Auditory neuropathy 18 (6)

96
Role of ASSR in Frequency-Specific Estimation of
Hearing Sensitivity in Infancy
OAE/ABR Screening Refer Outcome
Normal? Wave I Wave I-V 20 dB nHL
Abnormal ABR or No Response
Click ABR
Delayed Wave I?
ASSR
Wave I only? CM only?
Tone Burst ABR or OAEs
Bone Conduction ABR
Auditory Neuropathy
97
Auditory Steady State Responses (ASSRs) Pros and
Cons for Clinical Use
  • Advantages (Pros)
  • Reasonably frequency specific stimuli
  • Can be used for electrophysiologic assessment of
    severe to profound degree of hearing loss in
    infants and young children
  • Clinical devices now available
  • Automated analysis
  • Potential disadvantages (Cons)
  • Require very quiet state of arousal
  • Less accurate in normal hearing (especially low
    frequencies)
  • Limited anatomic site specificity
  • Analysis difficult with bone conduction
    stimulation

98
ASSR Lingering Clinical Questions
  • Are the neural generators for the ASSR well
    defined?
  • Are there maturational effects on ASSR from
    premature infants through childhood?
  • Is test time equivalent for ASSR vs. tone burst
    ABR?
  • Can ASSR be recorded from non-sedated patients?
  • What is the effect of sedation and anesthesia on
    ASSR?
  • How closely correlated are ASSR and pure tone
    hearing thresholds?
  • Can ASSR be used in estimation of bone conduction
    auditory thresholds?

99
ASSR Lingering Clinical Questions and Concerns
  • Are the neural generators of the ASSR well
    defined in humans?
  • No …
  • Animal findings on ASSR generators are not
    directly related to the ASSR in humans
  • Faster modulation stimulus rates (e.g., gt 60 Hz)
    elicit ASSR from the brainstem, whereas slower
    modulation rates produce cortical ASSR
  • Human ASSR probably reflects an overall summed
    activity across all stations along the
    ascending auditory system (Dimitrijevic Ross,
    2008)
  • Its not clear whether ASSR is generated by
    ipsilateral or contralateral neural dipoles, or
    both (Herdman et al, 2002)
  • State of arousal (e.g., awake, sleep, sedated,
    anesthetized) influences the ASSR neural
    generation site. Lower state of arousal
    associated with more caudal neural generators.
  • fMRI studies of ASSR neural generators are
    underway

100
ASSR Lingering Clinical Questions and Concerns
  • Are there maturational effects on ASSR from
    premature infants through childhood?
  • ASSR amplitude increases and threshold decreases
    during from to 1 chronological year
  • ASSR SNR smaller in pre-mature versus post-term
    infants (Rec postpone ASSR until after term
    birth date)
  • Changes are due to external ear, middle ear,
    cochlear, and neural maturation
  • Tone burst ABR is more reliable and accurate for
    threshold estimation in the neonatal period
    (Rance et al, 2006)

101
Maturation of ASSR in Infancy (Rance, 2008)
50
40
ASSR Threshold (dB HL)
30
20
10
0 2 4
6 52
Chronological Age (Weeks)
102
ASSR Lingering Clinical Questions and Concerns
  • Is test time equivalent for ASSR vs. tone burst
    ABR?
  • Yes … for a skilled clinician the test time for
    tone burst ABR and ASSR are equivalent, or test
    time for ABR is shorter.
  • ASSR requires conservative statistical
    confirmation of the response for a single
    stimulus intensity level
  • ABR detection with visual inspection takes into
    account findings at other intensities, and even
    other stimulus frequencies
  • Replication of ABR waveforms contributes to
    confident identification of the response
  • Noise interferes more with analysis of ASSR than
    ABR

103
ASSR Lingering Clinical Questions
  • Can ASSR be recorded from non-sedated patients,
    and what is the effect of sedation and
    anesthesia?
  • Modest amounts of muscular (myogenic) noise have
    major impact on automated detection of ASSR near
    threshold where response amplitude is small
  • The effect of sleep versus wakefulness on ASSR in
    infants has not been investigated (Cone-Wesson,
    2008)
  • Detection of ASSR in awake versus sleeping
    patients varies depending on the modulation
    frequency (e.g., 40 vs. 80 Hz) and the carrier
    frequency of the stimulus (e.g., 500 Hz versus
    2000 Hz)
  • Sedation and anesthesia suppresses amplitude of
    ASSRs elicited by slow modulation frequency
    (e.g., 40 Hz) generated in thalamo-cortical
    pathways and dependent on gamma rhythms
  • Anesthesia improves SNR in ASSR measurement with
    high modulation frequencies (reduces EEG and any
    myogenic noise)

104
Anatomy Physiology of ASSR Generators Not
Precisely Defined
Slower modulation rates (lt 60 Hz) Cortical
regions Faster modulation rates (gt 60 Hz)
Brainstem
105
ASSR Lingering Clinical Questions
  • Is it possible to elicit an artifactual or
    bogus ASSR?
  • With an early version of the MASTER device,
    artifactual spurious ASSRs were reported for
    stimulus intensity levels of gt 100 dB HL in
    patients with cochlear implants (cochlear
    function) who could not hear the stimuli (Small
    Stapells, 2004 Gorga et al, 2004 Jeng et al,
    2004 )
  • With the same ASSR device, bogus bone conduction
    ASSRs were recorded for stimulus intensity levels
    of 35 to 55 dB HL (Jeng et al, 2004)
  • Measurement errors are attributed to aliasing of
    stimulus artifact with slow analog-to-digital
    conversion rates (e.g., 500 or 1000 Hz) that are
    integral multiples of the carrier frequency (Smal
    Stapells, 2008)
  • With current devices, ASSR can be recorded
    confidently at high intensity levels with
    air-conduction stimuli
  • ASSR can be recorded confidently for modest bone
    conduction stimulus levels, e.g.,
  • 40 dB HL at 500 Hz
  • 50 dB HL at 1000 and 2000 Hz
  • 60 dB HL at 4000 Hz

106
ASSR Lingering Clinical Questions
  • How closely correlated are ASSR and pure tone
    hearing thresholds?
  • The difference between ASSR thresholds and
    behavioral pure tone thresholds is greater for
    normal hearing versus hearing impaired persons.
  • Differences between ASSR versus behavioral
    thresholds are smallest for infants, perhaps due
    to inaccuracy in behavioral measurements.
  • Both correction factors and statistical
    regression equations are used to estimate
    behavioral auditory thresholds from ASSR
    thresholds.
  • Data are lacking on the comparative accuracy of
    behavioral threshold estimation for different
    ASSR devices.

107
Maturation of ASSR in Infancy (Vander Werff,
Johnson Brown, 2008)
Normal hearing adults
25
Hearing-impaired adults
20
Hearing-impaired infants and children
15
Weighted Average ASSR vs. Behavioral Threshold
Difference Across Studies (dB HL)
10
5
500 1000 2000
4000 Stimulus (Carrier) Frequency in Hz

108
Auditory Electrophysiology in Audiology Today
Best and Future Practices
  • Electrocochleography (ECochG) in the diagnosis of
    auditory neuropathy
  • Maximizing efficiency and minimizing test time in
    frequency-specific ABR estimation of auditory
    thresholds in infants
  • Techniques and technology for diagnostic ABR
    assessment without sedation or anesthesia
  • Auditory steady state evoked response (ASSR) in
    pediatric audiologic assessment Pros, cons
    questions
  • Brainstem and cortical auditory evoked responses
    in auditory processing disorders (APD)

109
Auditory Evoked Responses Objective
Site-Specific Indices of Auditory System Function
P300 ALR AMLR ABR ECochG
110
Summary of APD Assessment With AERs Strengths
and Limitations of Different Responses
  • Electrocochleography (ECochG)
  • Limited value in APD assessment
  • Essential in diagnosis of auditory neuropathy
  • Auditory brainstem response (ABR)
  • Can be recorded in infants and young children
  • Conventional click stimulus is simple
    (non-speech)
  • Auditory middle latency response (AMLR) auditory
    late response (ALR)
  • Can be recorded with ABR devices
  • Modify test parameters as needed (e.g., slow
    rate, low HP filter setting)
  • True measures of cortical auditory function
  • Auditory P300 response
  • Considered a cognitive response of high level
    auditory function
  • Can be recorded with speech stimuli
  • Mismatch negativity response (MMN)
  • Doesnt require attention to task
  • Requires sophistical analysis strategy
  • Reliability in individual patient may be problem
  • Not feasible as a clinical technique

111
Auditory Evoked Responses in APD Some Clinical
Indications
  • Infants and young children (less than 7 years)
  • More site-specific information is
    required/desired
  • e.g., risk for neurologic disease or disorder
  • Cognitive and/or attention deficits interfere w/
    audiologic assessment, even with appropriate
    medical management
  • Inconclusive behavioral test findings
  • Incomplete behavioral test findings
  • APD assessment data likely to be used in
    medical-legal or educational-legal proceedings

112
Auditory Evoked Responses in Auditory Processing
Disorders (APD) Clinical experience in
1990s (Hall Johnston, 2007)
113
APD Assessment With ABR Good News and Bad News
  • Advantages
  • Recorded with clinical instrumentation using
    accepted test protocols, procedures, and analysis
    strategies
  • Anatomy/physiology known
  • Highly-reliable in infants and young children
  • Age influences well-defined
  • Not influenced by state of arousal, behavioral
    response to sound (e.g, autism), medications
    (sedation, anesthesia, stimulants, etc.)
  • Recent development of techniques for
    speech-evoked ABR to assess auditory processing
    at brainstem level (e.g., Kraus et al)
  • Disadvantages
  • No information on auditory function rostral to
    brainstem (where dysfunction is often found in
    APD)
  • With click stimuli, mainly dependent on
    synchronous firing of onset neurons
  • Not a test of hearing

114
Speech-Elicited ABR (Northwestern University
Auditory Neuroscience Laboratory)
115
Speech-Elicited ABR (Nina Kraus and Colleagues)
  • Commercially available with Bio Logic BioMark
    device
  • Electrophysiological response that follows or
    mimics the characteristics of the speech signal
    /da/
  • Normative data are available for children between
    ages of 8 to 12 years
  • Test protocol
  • Child sits quietly in chair
  • Quiet subject condition enhanced by watching
    video
  • Test time of about 20 minutes
  • Three trials each averaged for 2000 stimuli
  • Three waveforms are averaged

116
Speech-Elicited ABR Selected Recent Publication
by Nina Kraus and Colleagues (see www.
communication.northwestern.edu/brainvolts )
  • Johnson KL, Nicol T, Kraus N. (2008)
    Developmental plasticity in the human auditory
    brainstem J Neurosci 28(15)4000-4007.
  • Song JH, Banai K, Kraus N. (2008) Brainstem
    timing deficits in children with learning
    impairment may result from corticofugal origins.
    Audiol Neuro-Otol 13335-344.
  • Johnson K, Nicol T, Zecker S, Kraus N. (2007)
    Auditory brainstem correlates of perceptual
    timing deficits. J Cogn Neurosci 19 376 - 385.
  • Banai K, Abrams D, Kraus N. (2007) Speech evoked
    brainstem responses and sensory-based accounts of
    learning disability. Int J Audiol 46524-532
  • Song JH, Banai K, Russo NM, Kraus N (2006) On the
    relationship between speech and nonspeech evoked
    auditory brainstem responses. Audiology and
    Neuro-Otology 11233 - 241.

117
Normative Data for Speech-Evoked ABR are
Appropriate for Children Within Age Range of 5 to
12 Years
118
Speech-Evoked ABR (Bio Logic Bio Map Program)
119
Speech-Elicited ABR (Nina Kraus and Colleagues)
  • ABR analysis
  • With template, identify and calculate latency for
    wave V and wave A
  • Abnormal findings include delayed latency and
    shallow slope
  • Abnormal findings are verified statistically with
    automated program
  • Effective intervention (auditory training) can be
    documented by changes in speech-elicited ABR

120
Characteristics of Normal versus Abnormal
Speech-Evoked ABR
121
Characteristics of Abnormal Speech-Evoked
ABR Reduced Amplitudes for Higher Frequencies
122
Speech-Evoked ABR Normative Criteria for
Automated Analysis After Wave V and A are Marked
123
Auditory Evoked Responses Objective
Site-Specific Indices of Auditory System Function
P300 ALR AMLR ABR ECochG
124
Dan Geisler, Ph.D. Discoverer of Auditory Middle
Latency Response (AMLR) in 1958
125
Auditory Middle Latency Response
(AMLR) Analysis
Pa (22 - 30 ms)
Pb
1 mV
Na
Amplitude (mV)
Nb
PAM
PAM Post-auricular muscle
100 ms
126
(No Transcript)
127
Origins of the Auditory Middle Latency Response
(AMLR) (Photograph adapted from F.E. Musiek)
Primary Auditory Cortex
Thalamus (Medial Geniculate Body)
128
Origins of the Auditory Middle Latency Response
(AMLR) (Photograph adapted from F.E. Musiek)
Primary Auditory Cortex (Superior Temporal
Gyrus)
129
Enhancing Detection of the Elusive Pb Wave Slow
stimulus (lt 1/sec), Low frequency stimulus (500
Hz), Very low high pass filter setting (1
Hz) Nelson, Hall Jacobson, 1997
130
Modification of the AMLR Test Protocol to Record
a Pb Component (ALR P1)
  • Stimulus Parameters
  • Type Tones (not clicks)
  • Frequencies Lower are better
  • Duration
  • rise/fall 5 ms
  • plateau gt 10 ms
  • Rate lt 1 signal/second
  • ISI gt 1 second (up to 5 or 6 seconds)
  • Acquisition Parameters
  • Electrodes Cz (versus Fz)
  • Analysis time gt 100 ms
  • Filters 0.1 - 100 Hz

131
Measurement and Non-Pathologic Factors
Influencing AMLR Recordings
  • Test Parameters
  • Filtering avoid restricted high-pass filter
    setting (e.g., 30 Hz) and use HP setting of lt 1
    Hz to detect Pb component
  • Stimulus intensity level avoid very high levels
    (PAM artifact)
  • Stimulus duration longer (gt 10 ms) is better
    (avoid clicks)
  • Stimulus rate slower rates for children and in
    pathology with very slow rate (lt 1/sec) to detect
    Pb component
  • Subject Factors
  • Age a factor under 10 years old and interacts
    with rate
  • Sleep AMLR more variable during sleep
  • Post-auricular muscle (PAM) artifact Avoid if
    possible
  • Sedation amplitude reduced and variable
  • Anesthesia typically suppresses AMLR activity
    (reticular formation generators)

132
(No Transcript)
133
Sensitivity and Specificity of the AMLR in the
Detection of Auditory CNS Dysfunction
  • Musiek F, Charette L, Kelly T, Lee WW, Musiek R.
    Hit and false-positive rates for middle latency
    response in patients with central nervous system
    involvement. JAAA 10 1999.
  • 26 adult control subjects and 26 patients with
    medically confirmed CANS lesions (mostly CVAs and
    lobectomies)
  • Two groups matched for hearing status and age
  • AMLR measured with hemispheric electrode array
    (C3 and C4)
  • Latency measured for Na and Pa
  • Amplitude measured for Na-Pa
  • ROC curves generated by plotting hit rate by the
    false-positive rate for different criteria, e.g.,
    absolute latency and amplitude, and differences
    in these parameters for ipsi versus contra AMLRs

134
Abnormal Patterns of AMLR with Right Hemisphere
Lesion Electrode Effect
Left Hemisphere C5
Right Hemisphere C6
Pa
Pb
V
V
RE
RE
Na
Na
LE
LE
Right Ear
Left Ear
135
Abnormal Patterns of AMLR with Right Hemisphere
Lesion Ear Effect
Left Hemisphere C5
Right Hemisphere C6
V
RE
V
RE
Na
Na
Pa
Pb
LE
LE
Na
Right Ear
Left Ear
136
Abnormal Patterns for Auditory Middle Latency
Response (AMLR) in Patients with Confirmed
Temporal Lobe Lesions (Musiek et al, 2007)
AMLR Component (Amplitude in
?V) Hemisphere Na-Pa Na Pa Side of
Lesion Mean 0.55 0.20 0.35 (SD)
(0.20) (0.14)
(0.24) Intact Side Mean 0.86 0.28 0.63
SD (0.21) (0. 15)
(0.27)
137
(No Transcript)
138
APD Assessment with AMLR
  • Advantages
  • Accepted test protocols and procedures
  • Primary auditory cortex origins known
  • Measureable in infants and young children (but
    complex interax bet/ age, stimulus rate, duration
  • Not influencd by state of arousal and behavioral
    response to sound (e.g, autism) and some
    medications
  • Disadvantages
  • influenced by sleep and sedatives
  • Requires hemispheric electrodes for
    neurodiagnostic info
  • Analyses strategies not well defined in CAPD
  • Few data on relation bet/ AMLR and behavioral
    CAPD findings

139
Auditory Middle Latency Response (AMLR) Pb
(P50) as Index of Sensory Gating (e.g.,
Boutros et al. Psychiatry Research 57 1995)
Pa
Pb (P50)
1 mV
Conventional AMLR
Pb (P50)
Amplitude (mV)
Habituation (sensory gating)
Pb (P50)
Attention
500 ms
ms
Signal 1
Signal 2
140
Auditory Evoked Responses Objective
Site-Specific Indices of Auditory System Function
P300 ALR AMLR ABR ECochG
141
Auditory Late Responses (ALRs) in APD Assessment
Which responses are feasible for clinical use?
  • Negative waves (obligatory or exogenous
    responses)
  • N1
  • N1b
  • N1c
  • N150
  • N400
  • sustained negativity (for duration of stimulus)
  • Positive waves
  • P2
  • Oddball paradigm (positive and negative waves)
  • processing negativity
  • MMN (mismatch negativity) response
  • P3 (P300)
  • P3a

142
Auditory Late Response (Cortical)
5mV
P2 (180 200 ms)
P1 (50 ms)
Amplitude (mV)
N2 (200 - 400 ms)
N1 (90 - 150 ms)
600 ms
Stimulus
143
Auditory Late Response Generators
P300 N2 P2 N1
144
Auditory Late Responses (ALRs) Test Protocol (1)
  • Stimulus parameters
  • Stimulus tones or speech signals (e.g., phonemes
    /da/ or /ga/)
  • Duration relatively long, e.g.,
  • 10 ms rise/fall
  • 30 ms plateau
  • Rate slow (lt 1/sec) amplitude increases until
    ISI gt 5 sec)
  • Polarity alternating (not important)
  • Intensity moderate (lt 70 dB nHL)
  • Repetitions (averages) lt 200

145
Auditory Late Responses (ALRs) Test Protocol (2)
  • Acquisition parameters
  • Analysis time
  • Total 600 ms
  • Post-stimulus 500 or 600 ms
  • Pre-stimulus 100 ms
  • Electrodes
  • Non-inverting Cz (and/or Fz and other scalp
    locations)
  • Inverting earlobes (linked)
  • Supra-orbital/canthus monitor eyeblink
  • Amplification lt 25,000
  • Filter settings
  • Band-pass 0.1 to 100 Hz
  • Notch off

146
Auditory Late Responses (ALRs) Effects of
Selected Subject Factors
  • Age
  • Developmental changes
  • Maturation through at least 10 to 12 years of age
  • N1 and P2 amplitude decreases, and P3 amplitude
    increases, with development
  • Latency decreases with development
  • Advancing age
  • Gradual latency increase gt 20 years of age for
    all auditory late responses
  • Attention
  • Variable for different ALR components (for P2 and
    P3, not N1)
  • Sleep
  • Stage of sleep affects ALRs
  • Variability in sleep stages 3 and 4
  • Responses in rapid eye movement (REM) sleep
    equivalent to awake state
  • Changes in amplitude and latency can document
    effective intervention for APD (see Kraus and
    others)

147
Effectiveness of A Computer-Based Program for
Development of Auditory Processing Skills
Documentation with the ALR
  • Hayes, Warrier, Nicol, Zecker Kraus. Neural
    plasticity following auditory training in
    children with learning problems. Clinical
    Neurophysiology 114
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