Clinical applications of otoacoustic emissions in Industry. Prof. Dr. B. Vinck, MSc, PhD University of Ghent, Belgium

Transcription

1 Clinical applications of otoacoustic emissions in Industry Prof. Dr. B. Vinck, MSc, PhD University of Ghent, Belgium

2 The 25th anniversary of the discovery of otoacoustic emissions (OAEs) [sounds that can be measured in the external ear canal following the presentation of an acoustic stimulus] was celebrated in 2003.

3 The past Cochlea is a passive system GEORG VON BEKESY

4 The past. Kemp s discovery that the ear makes sound while listening to sound had difficulty getting published Nature rejected his manuscript on the grounds that otoacoustic emissons would doubtless prove of little interest outside the community of clinicians concerned with the diagnosis of hearing impairment. The discovery of otoacoustic emissions (OAEs) sparked a revolution in our understanding of the physical basis of hearing. Ironically, it has been precisely in the area of clinical utility that the full potential of OAEs has yet to be realized.

5 Otoacoustic emissions Where are we today?

6 4 types of OAEs were described Otoacoustic Emissions Spontaneous OAE Evoked Otoacoustic Emissions (EOAE) Poststimulatory OAE Perstimulatory OAE Transient OAE SFOAE DPOAE

7 existing models of cochlear function were modified significantly to acknowledge the reality of active processing several studies tried to relate OAEs to several neural and psychoacoustical phenomena. emitted responses were described in a number of experimental species commonly used as research models of hearing impairment

8 OAE generation Exactly how OAEs arise and how they are propagated in the cochlea is still in debate Experimental and theoretical evidence demonstrates two different mechanisms of generation

9 Mechanism based taxonomy of OAEs Otoacoustic Emissions OAEs that arise by Linear Reflection OAEs that arise by Non-linear distortion Reflection Emissions due to coherent reflection from random impedance perturbations Distortion Emissions due to nonlinearities acting as sources of traveling waves SOAEs Due to standing waves caused by coherent reflection Evoked Emissions mechanisms Shera, 2004 A mixture of both mechanisms

10 OAE generation Exactly how OAEs arise and how they are propagated in the cochlea is still in debate Experimental and theoretical evidence demonstrates two different mechanisms of generation OAEs are generated as a by-product of the electromotile vibrations of the OHCs Presence of OAEs demonstrates that the cochlea act as a cochlear amplifier that enhances the sensitivity and frequency tuning of the vibration of the cochlear partition

11

12 Clinical applications From the beginning : three major applications of OAE testing in clinical settings became apparent : differential diagnosis of hearing loss hearing screening in difficult-to-test patients such as newborns serial monitoring of progressive hearingimpairment conditions

13 AUDITORY SCREENING Auditieve screening

14 AUDITORY NEUROPATHY

15 Since this recognition of the major clinical applications of OAEs, other uses have emerged : resolving the legitimacy of medico-legal claims involving compensatory payments for hearing loss based on the sensitivity of OAEs to the intactness of the OHC system and its susceptibility to noise-induced damage the use of emissions to measure the functional intactness of the descending auditory nervous system.

16 Since this recognition of the major clinical applications of OAEs, other uses have emerged : resolving the legitimacy of medico-legal claims involving compensatory payments for hearing loss based on the sensitivity of OAEs to the intactness of the OHC system and its susceptibility to noise-induced damage the use of emissions to measure the functional intactness of the descending auditory nervous system.

17 Relationship noise and OHC damage

18 IHC ROW 3 ROW 2 ROW 1 Evolution damage

19 Literature data Hall & Lutman (1999) : the various OAE measures have the potential to distinguish small changes in cochlear function from measurement uncertainty, and hence show promise for monitoring cochlear function in ears exposed to noise or other hazards.

20 Study : TTS : Growth & Recovery pattern assessed by OAE Protocol Vinck et al, 1999 Pre-stimulatory evaluation 60 minutes exposure 60 min. postobservation interval Post evaluation Audiometry Oto-admittance evaluation TEOAE s DPOAE s (DP-GRAM Every 10 minutes TEOAEs DPOAES Every 4 minutes TEOAEs DPOAES

21 Study : TTS : Growth & Recovery pattern assessed by OAE Results Transient OAE s Repro :: Globaal 90 Repro : 4 Khz No difference PER POST

22 Study : TTS : Growth & Recovery pattern assessed by OAE Results DPOAE s DP-GRAM 1538 Hz DP-GRAM Hz 4004 Hz 4358 Hz 4761 Hz DP-GRAM 4358 Hz DP-GRAM 4761 Hz DPOAE response levels : TTS growth and recovery DP-GRAM 5188 Hz Hz

23 Literature data Plinkert (1999) : The results suggest that TEOAE provides a more sensitive and more objective method of detecting a subtle noise-induced disturbance of cochlear function than do PTA.

24 Literature data Konopkwa (2000) : The purpose of this study was evaluation of the click evoked otoacoustic emission (TEOAE) and distortion-product otoacoustic emission (DPOAE) before and after shooting and comparison with conventional pure tone audiometry. Emissions seem to be more sensitive for monitoring early cochlear changes after shooting than pure tone audiometry.

25 Literature data Sliwinska et al. (2002) : The results of the study suggest that OAEs, are likely to become a valuable method for assessing early hearing damage caused by exposure to noise.

26 Literature data Lapsey-Miller (2004) : otoacoustic emissions show promise in detecting noise-induced inner ear changes

27 AUDIOMETRY OTOTACOUSTIC EMISSIONS Measures Hearing threshold Measures OHC damage Both are fruit!!!

28 60% Damage 1 ROW UHC No damage AUDIOGRAM Altschuler, 1992

29 Follow-up OAE study in industry (Vinck et al., submitted for publication, 2006)

30 Study population 626 employees (571 males, 71 females) Mean age : 43.3 yrs (SD = 9.4 yrs)

31 AGE DISTRIBUTION NOISE POPULATION 16% n = % n = 571 n = 55 er e Number of employees % 12% 11% 10% 7% 2% 1% 0% 0% % 3% 1 % 1% 1% 1% 0% 0% 0% 0% 0% Sex : Male Age (years) Sex : Female

32 Study population : A. Test population 626 employees (571 males, 71 females) Mean age : 43.3 yrs (SD = 9.4 yrs) Mean exposure duration : 15 yrs (SD= 11.4 yrs)

33 Number of employees Number of employee < 30 years years years Exposure duration (in years) years

34 Study population 626 employees (571 males, 71 females) Mean age : 43.3 yrs (SD = 9.4 yrs) Mean exposure duration : 15 yrs (SD= 11.4 yrs) Mean exposure level : 83.3 dba (SD = 9) [60-93 dba]

35 Study population : B. Control population 3500 Males and 440 Females Mean age : 44.2 years (SD = 8.3 years) Not exposed to industrial noise Used as a reference population for OAEs

36 Methods Dosimetry Pure-tone audiometry (2006 only) Otoacoustic Emissions (2005 and 2006) transient OAE & Distortion Product OAE

37

38 OAE - gram Reference population was used to construct an OAE gram, based on TEOAE and DPOAE measurements Reproducibility % are used as key parameter

39 Results 1. Influence of age

40 Pure-tone audiometry OAE-gram Hearing loss (db HL) yrs < 30 yrs yrs yrs yrs Repro loss in % (re: controls) < 30 yrs yrs yrs yrs yrs Hz 500 Hz 1000Hz 2000Hz 4000Hz 8000Hz 0 1.0Khz 2.0Khz 3.0Khz 4.0Khz 5.0Khz 6.0Khz 1.5Khz 2.5Khz 3.5Khz 4.5Khz 5.5Khz 6.5Khz Age Frequency in Hz

41 Pure-tone audiometry OAE-gram Hearing loss (db HL) yrs < 30 yrs yrs yrs yrs Repro loss in % (re: controls) < 30 yrs yrs yrs yrs yrs Hz 500 Hz 1000Hz 2000Hz 4000Hz 8000Hz 0 1.0Khz 2.0Khz 3.0Khz 4.0Khz 5.0Khz 6.0Khz 1.5Khz 2.5Khz 3.5Khz 4.5Khz 5.5Khz 6.5Khz Age Frequency in Hz

42 20 15 DP-GRAM < 30 yrs yrs yrs yrs yrs Hz 1189Hz 1682Hz 2378Hz 3364Hz 4757Hz 6727Hz 1000Hz 1414Hz 2000Hz 2828Hz 4000Hz 5657Hz 8000Hz

43 TEOAE Band repro < 30 yrs Repro in % yrs yrs Same tendency for SNR & Response levels REPRO1K REPRO1.5K REPRO2K REPRO3K REPRO4K yrs +60 yrs

44 Results 1. Influence of age 2. Influence of exposure duration (corrected for age)

45 AUDIO Hearing Loss in db (HL) at 4 khz (1) (2) (3) (4) (5) < 5 yrs 5-10 yrs yrs yrs yrs 10 5 Exposure time e xpcode

46 OAE-GRAM Repro loss in % (re: Control) at 4 khz (1) (2) (3) (4) < 5 yrs 5-10 yrs yrs yrs 10 (5) yrs e xpcode

47 Pure-tone audiometry OAE-gram Hearing loss (db HL) < 5 yrs 5-10 yrs yrs yrs yrs A250Hz A500Hz A10 00H z A2000 Hz A4000H z A80 00H z Repro loss in % (re: controls) Khz 2.0Khz 3.0Khz 4.0Khz 5.0Khz 6.0Khz 1.5Khz 2.5Khz 3.5Khz 4.5Khz 5.5Khz 6.5Khz Exposure time Frequency in Hz

48 Results 1. Influence of age 2. Influence of exposure duration (corrected for age) 3. Influence of exposure level

49 Influence of exposure level No significant difference on OAEs and Audiometry

50 Results 1. Influence of age 2. Influence of exposure duration (corrected for age) 3. Influence of exposure level 4. Follow-up

51 Repro loss in % (re: controls) p < Deterioration of 3-10 % esp. Low-Mid frequencies OAE-gram Khz 2.0Khz 3.0Khz 4.0Khz 5.0Khz 6.0Khz 1.5Khz 2.5Khz 3.5Khz 4.5Khz 5.5Khz 6.5Khz

52 Results 1. Influence of age 2. Influence of exposure duration (corrected for age) 3. Influence of exposure level 4. Follow-up Relation audiometry - OAE

53 1kHz 2kHz 4kHz 8kHz 1kHz -0,56* 2kHz -0,59* 4kHz -0,61* 8kHz -0,58* * Significant at p < 0.05 level

54 Conclusions OAEs have proven useful in monitoring the effects of agents, such as loud sounds on cochlear function There is accumulating evidence that it is possible to detect such adverse effects of noise on OHC function using OAEs before a related hearing loss can be detected by pure-tone audiometry. OAEs supply unique information about cochlear function in the presence of hearing problems It is this capability that make this technique valuable to use in a hearing conservation program for the early detection and as a complementary technique to the audiometric-test battery