Otoacoustic Emissions Textbook Overview of otoacoustic emissions - PowerPoint PPT Presentation

still from Avan & Bonfils (2004) Thd DPOAE TEOAE (in 11 ears)

Recreational Exposure • 21 participants listened to 1 hour of music from personal music players. Repeated six times. • No change in DPOAE or hearing thresholds even in those listening at > 75% of volume setting (97 – 102 dBA). • TEOAE show statistically significant shift in these listeners of -0.47 dB at 2 kHz and -0.70 dB at 2.8 kHz.

338 volunteers (US Navy) evaluated before and after 6-month training where they were noise exposed.

On average hearing thresholds did not change in a group of 75 volunteers.

Significant (-0.66 dB) change in TEOAE amplitude.

Significant (-1.28 dB) change in DPOAE amplitude. Greatest change at lowest stimulus level.

In 18 ears with PTS, the likelihood of PTS increased with decreasing OAE amplitude.

Hair cell response returns to normal; Long term synaptic loss and loss of neural amplitude; Loss of ganglion cells is delayed even more.

Six Reasons Why OAEs Will Never Replace the Audiogram nor Accurately Estimate Hearing Loss (1-3)  OAEs measurement is dependent on inward and outward propagation of energy through the middle ear (e.g., abnormal OAEs with normal hearing sensitivity )  OAEs are more sensitive to cochlear dysfunction than the audiogram (e.g., abnormal OAEs with normal hearing sensitivity)  OAEs are electrophysiologic measures while the audiogram is behavioral (e.g., normal OAEs with abnormal audiogram)

Six Reasons Why OAEs Will Never Replace the Audiogram nor Accurately Estimate Hearing Loss (4-6)  OAEs are produced by OHCs, whereas the audiogram is dependent on IHCs (e.g., normal OAEs with abnormal audiogram)  OAEs are pre-neural, whereas the audiogram is dependent on retrocochlear pathways (e.g., normal OAEs with abnormal hearing sensitivity )  OAEs reflect OHC integrity, whereas the audiogram measure hearing (e.g., normal OAEs with abnormal audiogram)

Otoacoustic Emissions in Audiology Today: Limitations in use of OAEs by clinical audiologists  Over reliance on screening protocols, e.g.,  Recording within a limited frequency region  Simple “ pass ” versus “ fail ” outcome  Questionable techniques for measurement and analysis, e.g.,  Single trial or run (remember … “ If your OAEs do not repeat, your test is not complete! ”  Failure to achieve lowest possible noise levels (< 95%ile for adult normal subjects)  Analysis limited to “ present ” or “ absent ”  Not applied in a variety of patient populations  Only used as a screening technique for newborn infants  Not applied routinely in the initial diagnostic audiologic assessment of most patients (children and adult)  False assumption  OAEs will provide the same information that is available from the audiogram … “I know the patient has a sensorineural hearing loss … why should I perform OAEs? …

Update on Otoacoustic Emissions: Basic Science to Clnical Application Morning Session  Introductions  Historical evolution of OAEs  Cochlear physiology and OAEs  Prospects of clinical applications  Break  OAE types and taxonomy  Mechanisms of OAE generation  Complex generation of DPOAEs  DPOAEs and hearing thresholds  OAEs as early indicators of cochlear pathology

But That ’ s Not the Entire Story (See Chapter 3 of Dhar & Hall, 2012)

Phase is a Factor in the Generation of OAEs Shera, 2009

Regular Spacing of Spontaneous OAEs

Coherent Reflection Filtering Zweig, Shera (1995 on) input Incoming signal is “ reflected ” stapes randomly by outer hair cells; base apex some reflections are coherent and contribute to the outward- traveling energy. Coherent reflectors near the peak region of the traveling wave have enough magnitude to contribute significantly to ear-canal OAE.

Inhibition (Suppression) of Otoacoustic Emissions: Role of the Efferent Auditory System (See Chapter 9 of Dhar & Hall, 2012)

Classification STIMULUS Without stimulation Spontaneous Stimulated Transient,Distortion product,Stimulus frequency MECHANISM Distortion Reflection Spontaneous Mixed DPOAEs TEOAEs SFOAEs

Types of OAEs: Conventional Classification Type Stimulus Prevalence Spontaneous none < 70% Evoked transient click or tone burst > 99% distortion product two pure tones > 99% stimulus frequency continuous tone ?? %

Transient Otoacoustic Emissions (TEOAE)

Distortion Product Otoacoustic Emissions (DPOAEs)

Update on Otoacoustic Emissions: Basic Science to Clnical Application Morning Session  Introductions  Historical evolution of OAEs  Cochlear physiology and OAEs  Prospects of clinical applications  Break  OAE types and taxonomy  Mechanisms of OAE generation  Complex generation of DPOAEs  DPOAEs and hearing thresholds  OAEs as early indicators of cochlear pathology

Update on Otoacoustic Emissions: Basic Science to Clnical Application Morning Session  Introductions  Historical evolution of OAEs  Cochlear physiology and OAEs  Prospects of clinical applications  Break  OAE types and taxonomy  Mechanisms of OAE generation  Complex generation of DPOAEs  DPOAEs and hearing thresholds  OAEs as early indicators of cochlear pathology

Update on Otoacoustic Emissions: Basic Science to Clnical Application Morning Session  Introductions  Historical evolution of OAEs  Cochlear physiology and OAEs  Prospects of clinical applications  Break  OAE types and taxonomy  Mechanisms of OAE generation  Complex generation of DPOAEs  DPOAEs and hearing thresholds  OAEs as early indicators of cochlear pathology

Mixed DPOAEs f 1 f 2 middle ear outer ear f 2 f 1

middle ear outer ear f 2 f 1 composite reflection nonlinear Talmadge, Long, Tubis & Dhar (1999); JASA model

Talmadge, Long, Tubis & Dhar (1999); JASA

Relation Between OAE Amplitude and Hearing Loss DPOAE 65/55 dB SPL TEOAE 80 dB SPL WNL OAE (Amplitude > 95%ile) Amplitude Normal Present but not normal No OAE No OAE (OAE – NF < 6 dB) -10 0 10 20 30 40 50 60 Hearing Level in dB HL

Best bet for threshold prediction: Input/Output Functions

Improving Predictions Using I/O Functions  Plot DPOAE pressure (in Pascals not dB SPL).  Fit linear function to first few points reliably above the noise floor.  Threshold is the stimulus level that yields 0 Pa DPOAE amplitude per the fitted line. (Boege & Janssen, 2002)  Two slope method (Neely et al., 2009) leads to further improvement. Neely et al., 2009

Prediting thresholds from DPOAE levels has not been successful. Categorization of ears works to some extent. Screening works the best. Gorga et al., 1997

Gorga et al., 1997

Gorga et al., 1997

OAEs: Abnormal OHCs and loudness recruitment “ The phenomenon of loudness recruitment appears to be the psychoacoustic expression of the loss of a large component of outer hair cells and the concurrent preservation of a large component of inner hair cells and type I cochlear neurons. ” Schuknecht HF. Pathology of the Ear (2nd ed). 1993, p. 91

Diagnostic Application of OAEs: Findings for multiple frequencies vs. normal region Screening = pass (DP – NF = > 6 dB) Diagnostic = abnormal Normal region Noise floor

Analysis of DPOAE Amplitude: Diagnostic Applications Present but No Normal Abnormal OAE

Steps in Analysis of DPOAE Findings  Perform analysis at all test frequencies  Verify adequately low noise floor (< 90% normal limits)  Verify replicability of DPOAE amplitude (+/- 2 dB) from at least two runs  Is DP - NF difference > 6 dB?  Yes? DPOAEs are present  No? There is no evidence of DPOAEs  Is DP amplitude within normal limits?  Yes? DPOAEs are normal  No? DPAOEs are abnormal (but present)

EAR CANAL FACTORS INFLUENCING OAE MEASUREMENT  Non-pathologic  probe tip placement, size, or condition  probe insertion depth  standing waves  cerumen or debris  vernix casseous (healthy newborn infants)  Pathologic  stenosis  external otitis

CLINICAL APPLICATION OF OTOACOUSTIC EMISSIONS (OAE): Trouble-shooting  Minimizing the effects of noise on OAE recordings  eliminate extraneous noise sources in test room  close door to test room  insert probe deeply  secure probe cord  instruct patient to remain quiet and still (if feasible)  position test ear away from equipment  modify protocol (to frequencies > 2000 Hz)

VENTILATION TUBES and OAEs  Daya et al. (1966). Otoacoustic emissions: Assessment of hearing after tympanostomy tube insertion. Clin Otolaryngol 21: 492-494.  Owens, McCoy, Lonsbury-Martin, Martin. (1993). Otoacoustic emissions in children with normal ears, middle ear dysfunction, and ventilating tubes. Amer J Otol 14: 34-40.  Tilanus. Stenis, Snik.(1995). Otoacoustic emission measurements in evaluation of the effect of ventilation tube insertion in children. Annals of ORL 104: 297-300.  Richardson, Elliott, Hill. (1996). The feasibility of recording transiently evoked otoacoustic emissions immediately following grommet insertion. Clin Otolaryngol 21: 445-448.  Cullington, Kumar, Flood. (1998). Feasibility of otoacoustic emissions as a hearing screen following grommet insertion. Brit J Audio 32: 57-62.

AUDIOGRAM & DPOAEs: Pre-ventilation tubes (5 y.o. girl) Right Ear KHz Left Ear .50 1K 2K 3K 4K 6K 8K .50 1K 2K 3K 4K 6K 8K 0 0 dB HL 20 20 40 40 ST = 20 60 60 ST = 40 80 80 AC BC

AUDIOGRAM & DPOAEs: Ventilation tubes (4 mos. later before APD eval.) Right Ear KHz Left Ear .50 1K 2K 3K 4K 6K 8K .50 1K 2K 3K 4K 6K 8K 0 0 dB HL 20 20 40 40 ST = 15 ST = 15 60 60 80 80 AC BC

Non-factors in OAE Interpretation  Non-Factors  diurnal effects (time of day)  genetics  body temperature  body position  anesthetic agents (w/ normal middle ear status)  state of arousal (attention to stimulus)

Relation Between OAE Amplitude and Hearing Loss DPOAE 65/55 dB SPL TEOAE 80 dB SPL WNL OAE (Amplitude > 90%ile) Amplitude Normal Present but not normal No OAE No OAE (OAE – NF < 6 dB) -10 0 10 20 30 40 50 60 Hearing Level in dB HL

Diagnostic Application of OAEs: Findings for multiple frequencies vs. normal region Screening = pass (DP – NF = > 6 dB) Diagnostic = abnormal Normal region Noise floor

Analysis of DPOAE Amplitude: Diagnostic Application Present but No Normal Abnormal OAE