Transcript MAC: Electrophysiology Lecture

Auditory Evoked Potentials:
Selected Measures
Lecture and Lab
Bruce Edwards, Au.D.
University of Michigan Health System
Michigan Audiology Coalition Meeting
E. Lansing, MI
October 17, 2014
Intro to me
• Asst Director of Audiology & Electrophysiology, UMHS
• 35 years of clinical experience evaluating patients with
auditory, vestibular, facial measures, >20 years in IOM
includes training staff, educating students and
colleagues
• As CMU grad student w/ two others, assembled an ABR
device from components in speech lab; recorded my
ABR using huge loudspeaker & a tiny oscilloscope with
lots of manual switches
• Don’t pass up opportunities!
MAC: AEP Lecture [50 - 60 mins]
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Variety and uses of AEP
Effects upon AEP
Quality control measures throughout
Three case studies
Questions
Hands-on /Demo lab – thanks to Audiology
Systems and to Gordon Stowe for bringing
equipment to demo; may need volunteers-
Lab component [60 mins]
• Otometrics CHARTR ep
• IHS Smart EP
• IHS baby simulator
Audiology Systems
• Biologic Nav Pro,
neurodiagnostic twochannel; possibly ASSR
Gordon Stowe
EPs used clinically
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Auditory brainstem response
Electrocochleography
Cochlear microphonic
Otoacoustic emissions, a low-level sound emitted
by the cochlea, so not an AEP…
• Vestibular evoked myogenic potentials
• Middle latency potentials
• Later latency potentials
Quality Measures and AEP Recordings
To achieve replicable and valid clinical measures:
• Improve the SNR / Fsp (single-point F ratio) /
Fmp (multiple-point F ratio)
– Relax patient, patient’s parents
• Have a goal for each encounter
• Calibrate yourself & your methodology
• Be a skillful collaborator (work with patients,
deliver your results, plan next steps in a
patient-centric fashion)
Auditory
Brainstem
Response
Arguably the most
commonly-used form of
AEP in Audiology:
• a far-field potential
recorded from the
ascending auditory
pathway
• Its versatility as a
measure of the
neurologic auditory
system is unmatched by
other measures
http://tx.technion.ac.il/~eplab/EPs/sld002.htm
Generator sites for ABR
Auditory system’s blood supply is crucial,
two important systems
• #1 Vertebrobasilar
distribution:
• Cochlea, CN VIII
• Upper spinal cord
• Medulla
• Cerebellum
• Pons
• Midbrain
• Temporal & occipital
lobes
• OAE, ECoG, ABR
Important systems
• #2 Internal Carotid:
• Most of the anatomical
area rostral to the
brainstem
• Hippocampus (medial
temporal lobe)
• Cerebral hemispheres
• AMLR, Late Responses,
P300, Mismatched
Negativity [MMN]
ECoG
Generation of SP, AP, CM
requires inner and outer
hair cells of basilar
membrane brush or
push against tectorial
membrane, with
eventual release of
neurotransmitters to
spiral ganglion neurons
http://tx.technion.ac.il/~eplab/EPs/sld001.htm
Evoked
Otoacoustic
emissions
-Transient OAE
-Distortion product OAE
-Others are available but
have been taken up by
clinicians given the
relative ease of use and
benefits derived by TE
and DP OAEs
http://www.mimosaacoustics.com
/products/dpoae.html
Vestibular
evoked myogenic
potentials
-A short latency response in
posterior neck muscles, or
the eyes, in response to loud
clicks
- This reflex arc for cVEMP
includes ear, saccule, IVN,
vestibular nuclei,
vestibulospinal tract, CN XI
(accessory n.), SCM
-Used to determine the
function of the utricle and
saccule of the inner ear’s
otolith organ in patients with
-VIII n. lesions that involve
inferior vestibular nerve
(cVEMP)
-suspected superior canal
dehiscence
-Meniere’s disease
P1/13
P2
N1 / 23
www.mayo.edu/mayo-edu-docs/mayo-clinic-audiologyconference-documents/burkard-shepard-handout.pdf
Auditory Middle
Latency
Potentials
Generators include
thalamocortical pathways,
mesencephalic reticular
formation, inferior
colliculus;
Used to calculate lower
freq hearing, objectify
complaints of tinnitus;
response matures in
adolescence,
sleep/sedation effects are
seen in AMLR amplitudes
Note 1) slow negative-10
potential, precedes the
AMLR Na, and 2) possible
influence of PAM on early
AMLR components
www.tinnitusjournal.com/deta
lhe_artigo.asp?id=478
www.audiologyonline.com/articles/goodpractices-in-auditory-brainstem-827
Auditory Latelatency
Potentials
Generators for later
responses include
thalamic projections
into the auditory
cortex, primary
auditory cortex,
supratemporal plane,
tempoparietal
association complex,
lateral frontal cortex
http://tx.technion.ac.il/~eplab/EPs/sld004.htm
Auditory processing
modulated by auditory
experiences
http://en.wikipedia.org/wiki/File:G
ray685.png
http://theluciddreamsite.com/thedorso-lateral-prefrontal-cortexand-lucid-dreaming.html
Selected uses for AEP
• Newborn hearing screening
• Followup infants referred from EHDI
• Preoperative planning for intraoperative
neurophysiologic monitoring
• Confirmation of results of audiologic
assessments
• Screening for VIIIth nerve lesions
• Estimates of nerve conduction in patients with
systemic neurologic disease
Suggestions to maximize quality
opportunities in clinical AEP recordings
• Provide uncomplicated, jargon-free instructions for patients or
parents
• Be a facilitator of the appointment
-use clear, simple instructions and have the patient acknowledge
-be flexible and intuitive
• Consider the best stimulating and recording parameters for the test
that you will conduct; it will vary depending on patient age and your
intentions
• Importantly, have a plan to reach a specific goal for each patient.
Example: “What is the most important outcome for this encounter?”
– Ex.: Averaged responses at intensity levels less than admitted
pure tone levels
– Ex.: Preoperative responses used for IOM (or to confirm lack of
response from affected side)
Suggestions as you work with families
As Mom goes, so goes baby:
• “Nothing will hurt your baby.”
• “I need your help during your baby’s appointment.”
• Parents often want to know if/how they can assist
• Direct families to arrive hungry and sleepy; arrive before
appt if traveling a distance (during which newborn will
sleep)
• Parents should play with baby after arrival
• Complete skin prep of electrode sites before feeding,
sleeping
• If doing bone conduction ABR, use pre-auricular or earlobe
sites for inverting/reference electrode (avoid a mastoid
location)
EP orientation
-Balanced impedances
across leads are crucial
-Active / positive electrode
on vertex (could be
cervical neck to increase
the amplitude of ABR wave
V)
-Reference / negative
electrode placed at ear
level – mastoid, earlobe,
pre-auricular skin (for b/c
ABR studies)
-Ground on forehead or
contralateral ear
Differential amplifier schematic used in
common mode rejection: signals common to
two lines opposite in polarity cancel before
amplification and output
Environmental & drug effects on AEP
• Post-auricular muscle artifact: reduce EMG, get patient
comfortably positioned for ~30-90 min visit
• Electromagnetic energy in electrical lines & outlets transmitted to
instrumentation and/or recording electrode leads
• EKG can average into averaged responses; so
avoid placing ABR leads across patient’s chest;
pacemakers/defibrillators may make recordings challenging
• In operating room (OR) or outpatient clinic (OPC)
– Inhalational anesthetics (ex: isoflurane) cause dose-dependent,
predictable delay in waves III-V of ABR OR
– Conscious sedatives (ex: chloral hydrate) with no known effects
on sensory nerve conduction; sedation is short lasting and
poorly-predicted; core body temp will induce IPL changes OPC
Three case studies of AEP
#1 Hearing Threshold Estimation (Audiology’s
bread & butter)
#2 Preoperative Evaluation of Auditory System
in a patient with large, compressive mass
#3 Intraoperative Neurophysiologic Monitoring:
hearing preservation attempt, vestibular
schwannoma
#1 case study
Hearing Threshold Estimation: “KR”
Indications for Procedure:
• 6 wk female born w/o incident or concerns at U-M Von
Voigtlander Women's Hospital; referred bilaterally for
additional testing in August
• Seen in f/u at the University of Michigan C. S. Mott
Children's Hospital for ABR evaluation of peripheral
hearing sensitivity
• no family history of hearing loss
• startles to loud sounds at home, per parents
• no risk factors for progressive hearing loss
• procedure was described in detail to the mother and
grandmother
Recognize the pattern?
www.google.com/images?hl=en&q=pictures+of+ABR+responses&gws_rd=ssl&sa=X&oi=image_result_group&ei
=6aAtVLbCEZCsyASMroHQBw&ved=0CBQQsAQ
#1 case studyHearing Threshold Estimation: “KR”
POVR: Point Optimum Variance Ratio algorithm; pass > 3.5
#1 case studyHearing Threshold Estimation: “KR”
#1 case studyHearing Threshold Estimation: “KR”
#1 case study
Hearing Threshold Estimation: KR
Results
Test and Findings:
• DPOAE used to assess cochlear outer hair cell function between
2000 and 6000 Hz bilaterally: OAE present bilaterally ruling out
mild sensorineural or neural hearing loss
• ABR: Recording electrodes placed on forehead and ears; insert
earphones used to deliver click and 1 kHz tone-burst stimuli
monaurally at various intensities
• ABR waveforms document near-threshold Wave V responses
replicable down to 20 dBnHL in each ear suggesting normal
peripheral hearing in mid-to-high frequencies
Impression:
• passed follow-up evaluation bilaterally
• results discussed with mother and grandmother, literature provided
re: normal speech, language, hearing development
• hearing should be reevaluated if needed
#2 case study
ABR preop in pt. with large mass lesion
in the right CPA/IAC
• 40-something woman in
1st trimester of her
pregnancy
• Complained of quickonset hearing loss,
tinnitus right ear
• Audiologic assessment
reveals unilateral SNHL
• Note the word rec score!
#2 case study
Pt. “BH” with large mass lesion in the
right CPA/IAC; soon after the delivery:
#2 case study
Pt. BH, large mass lesion in the right
CPA/IAC; soon after the delivery:
#2 case study
Pt. BH with large mass lesion in the right
CPA/IAC; intraop ABRs: examine
waveform at “end”
#2 case study
ABR in pt. BH with large mass lesion
OUTCOME
Preop Hearing
Postop Hearing
#3 case study
Pt. “CG”: vestibular schwannoma,
planned hearing preservation
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1 yr c/o intermittent
lightheadedness, NOS; delayed
surgery for ~ 6 months
Neurologist ordered MRI
Preop audio WNL, ABR I-III, 3.6 msec,
I-V @ 5.6 msec
DP OAE intact bilaterally
Vestibular testing revealed right
peripheral system weakness
#3 case study-patient “CG”
with vestibular schwannoma,
planned hearing preservation
#3 case study-patient “CG”
with vestibular schwannoma,
planned hearing preservation
(note scale differences)
Prior to incision (start of case)
Prior to closing (end of case)
#3 case study patient “CG” with vestibular
schwannoma, undergoing planned hearing
preservation: OUTCOME
• Patient survived the procedure without
neurological complications
• Patient’s mass lesion was completely removed
• Patient’s facial nerve function remained intact,
measured by triggered EMG measures (0.1 mA
threshold) & by patient’s postoperative function
• Patient’s hearing was preserved per ABR
throughout the case and by patient report after
surgery; post-op audio to be done
References
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www.scielosp.org/scielo.php?pid=S1020-49891997001000002&script=sci_arttext
informahealthcare.com/doi/abs/10.3109/00207458108985851
• http://www.audiologyonline.com/articles/good-practices-in-auditorybrainstem-827
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callierlibrary.wordpress.com/2010/02/17/auditory-brainstem-evoked-potentialsin-crack-and-multiple-drugs-addicts/
www.soc.northwestern.edu/brainvolts/documents/Kraus_Nichol_Encyclo_Neuros
ci_AEPs.pdf
tx.technion.ac.il/~eplab/EPSwhat.htm
trialx.com/curebyte/2012/11/14/otoacoustic-emission-photos-and-relatedclinical-trials/
www.mimosaacoustics.com/products/dpoae.html
www.ncbi.nlm.nih.gov/pmc/articles/PMC3342755/
http://www.ohioslha.org/pdf/Convention/2008%20Handouts/SC24-AUDMcCaslin.pdf
http://www.mayo.edu/mayo-edu-docs/mayo-clinic-audiology-conferencedocuments/burkard-shepard-handout.pdf
Kileny PR, Edwards BM, et al. Hearing improvement after resection of CPA
Meningioma….JAAA 9: 251-256, 1998
QUESTIONS?
Time for the demo/hands-on.
Thanks again to Audiology Systems
and to Gordon Stowe for their
support!
West Ann Arbor neighborhood