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Michigan Audiology Coalition Meeting E. Lansing, MI October 17, 2014

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Presentation on theme: "Michigan Audiology Coalition Meeting E. Lansing, MI October 17, 2014"— Presentation transcript:

1 Michigan Audiology Coalition Meeting E. Lansing, MI October 17, 2014
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

2 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!

3 MAC: AEP Lecture [50 - 60 mins]
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-

4 Lab component [60 mins] Otometrics CHARTR ep IHS Smart EP
IHS baby simulator Biologic Nav Pro, neurodiagnostic two- channel; possibly ASSR  Audiology Systems Gordon Stowe

5 EPs used clinically 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

6 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)

7 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

8 Generator sites for ABR

9 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

10 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]

11 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

12 Evoked Otoacoustic emissions
ILO 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

13 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

14 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

15 Auditory Late-latency Potentials
Generators for later responses include thalamic projections into the auditory cortex, primary auditory cortex, supratemporal plane, tempoparietal association complex, lateral frontal cortex Auditory processing modulated by auditory experiences

16 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

17 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)

18 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)

19 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

20 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

21 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

22 #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

23 Recognize the pattern?

24 #1 case study- Hearing Threshold Estimation: “KR”
POVR: Point Optimum Variance Ratio algorithm; pass > 3.5

25 #1 case study- Hearing Threshold Estimation: “KR”

26 #1 case study- Hearing Threshold Estimation: “KR”

27 #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

28 #2 case study ABR preop in pt
#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 quick-onset hearing loss, tinnitus right ear Audiologic assessment reveals unilateral SNHL Note the word rec score!

29 #2 case study Pt. “BH” with large mass lesion in the right CPA/IAC; soon after the delivery:

30 #2 case study Pt. BH, large mass lesion in the right CPA/IAC; soon after the delivery:

31 #2 case study Pt. BH with large mass lesion in the right CPA/IAC; intraop ABRs: examine waveform at “end”

32 #2 case study ABR in pt. BH with large mass lesion OUTCOME
Preop Hearing Postop Hearing

33 #3 case study Pt. “CG”: vestibular schwannoma, planned hearing preservation
1 yr c/o intermittent lightheadedness, NOS; delayed surgery for ~ 6 months Neurologist ordered MRI Preop audio WNL, ABR I-III, 3.6 msec, 5.6 msec DP OAE intact bilaterally Vestibular testing revealed right peripheral system weakness

34 #3 case study-patient “CG” with vestibular schwannoma, planned hearing preservation

35 #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)

36 #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

37 References / Kileny PR, Edwards BM, et al. Hearing improvement after resection of CPA Meningioma….JAAA 9: , 1998


39 Time for the demo/hands-on
Time for the demo/hands-on. Thanks again to Audiology Systems and to Gordon Stowe for their support!

40 West Ann Arbor neighborhood

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