Trajectory of the Aging Cochlea

Transcription

1 Trajectory of the Aging Cochlea Sumitrajit (Sumit) Dhar Professor & Chair Roxelyn & Richard Pepper Department of Communication Sciences and Disorders Fellow, Hugh Knowles Center for Hearing Science Northwestern University Evanston, IL IHS, September 2016

2 Learning Objectives Identify early signs of age-related hearing loss. Select the best tools for diagnosing agerelated hearing loss. Counsel patients about the likely trajectory of age-related hearing loss.

3 Cochlear mechanics and OAEs The life of the inner ear Clinical strategies for data quality Clinical parameters for data acquisition Case studies

4 Cochlear mechanics and OAEs The life of the inner ear Midlife crisis The elderly inner ear

5 Transient/Click Evoked Otoacoustic Emissions (TEOAE) Distortion Product Otoacoustic Emissions (DPOAE) Stimulus Frequency Otoacoustic Emissions (SFOAE) Spontaneous Otoacoustic Emissions (SOAE)

6 SFOAE 40 Level (db SPL) P Total at 40 db SPL P Total at 40 db SPL w/ suppressor Phase (cycles) = PSFOAE P Stimulus P SFOAE = P Total P Stimulus

7 Mechanics, Mechanisms, Modalities

8 Lessons from Kemp, 1978 Random noise recorded when closed cavity is stimulated with a click. Same stimulus in human ear shows response lasting beyond 10 ms TEOAE. We have to wait for the speaker to stop ringing. Continues to be the case; early TEOAE is not recorded. Different delays for responses to tone bursts of different frequencies cochlear origin.

9 Site of Generation Cochlea: observed delay in OAEs; recordings from BM & auditory nerve. Outer Hair Cells: concomitant ablation of OAEs and OHC (e.g., Davis et. al., 2002); loss of OAEs due to other insults associated with OHC damage (salicylate, noise, etc.). But where in the OHC?

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11 Prestin KO Liberman et al., 2004

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13 Verpy et. al., (2008); Nature Liberman et al., 2004

14 Cochlea Outer Hair Cell Stereocilia (transducer) Soma (?amplifier) Olivocochlear efferents Middle ear transmission

15 Frequency/Place Specificity

16 Idealized Spread of Excitation fp Stapes base apex

17 DPOAEs f2 f1 Stapes base apex

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19 SFOAE/CAP-STC IT fs fp fs Stapes base apex Damage

20 IT Experiments

21 Tone Exposure Experiments

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23 Normal Hearing Human Ears Charaziak, Souza, and Siegel, 2013

24 The Good News: SFOAE generation region in the chinchilla is much more localized at and above 3 khz. In humans, OAE generation regions appear to even be more restricted.

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26 DPOAEs f2 f1 2f1-f2 Stapes base apex

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28 65 db SPL 75 db SPL

29 The Good News: DPOAE generation area appears to be narrower in humans as compared to other laboratory animals. Stimulus levels up to 65 db SPL should yield place specific estimates of cochlear health.

30 OAEs are primarily produced by the outer hair cells. DPOAEs are most likely produced by steriociliary nonlinearities. OAE generation is generally frequency (place) specific. OAE generation is more place specific in the apical half of the cochlea. OAE generation appears to be more place specific in humans as compared to other species.

31 Cochlear mechanics and OAEs The life of the inner ear Clinical strategies for data quality Clinical parameters for data acquisition Case studies

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33 Frequency (khz) OAEs are vital signs of the life of the inner ear and allow exquisite monitoring of cochlear health.

34 Age related changes progress from the base to the apex of the cochlea. But when they start and how they progress is not established to our sa:sfac:on.

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36 Stevens et al., 1987

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38 with Jonathan Siegel Steve Zecker David Klodd Vickie Hellyer Rebecca Abel Jungmee Lee Gayla Poling Funding: National Institutes of Health [R01 DC008420]

39 Lee#et#al.,# 12 Ear#&#Hearing Poling# et#al.,# 14 JASA Souza#et#al.,# 14 JASA

40 Data from ongoing project att NU and UI Hospital clinics. Full sample stands at ~1199 individuals (10-65 yrs). 316 otologic normal individuals from phase I. 661 individuals with average thresholds across khz 20 db HL from phase II. Behavioral Thresholds DPOAEs SFOAEs khz; Different calibration in two phases khz; 55/40, 65/55, 75/75 db FPL khz, 40 db FPL

41 Thresholds between and 20 khz. DPOAE: Stereociliary nonlinearity boosted by electromotility. stapes input base apex Evoked OAEs between 0.75 and 20 khz SFOAE: Roughness in the cochlear impedance gradient causing reflection.

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43 *

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45 N=661; At least 35 in each bin yrs yrs 6-12 khz

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48 DPOAE Ear canal Middle ear Cochlea f 1 f 2 DPOAE base 1 f 2 f 1 2f 1 -f 2 2 apex Total DPOAE 1 2

49 Phase I & II: 5-yr bins starting at 10 yrs old; at least 55 in each bin N=997 55/40 db FPL

50 Phase I & II: 5-yr bins starting at 10 yrs old; at least 55 in each bin N=997 65/55 db FPL

51 Phase I & II: 5-yr bins starting at 10 yrs old; at least 55 in each bin N=997 75/75 db FPL

52 N=997; DPOAE Loss;75/75

53 N=997; DPOAE Loss;75/ yrs yrs 4-16 khz

54 55/40 65/55 75/75

55 Change in DPOAE levels with age (75/75 db FPL)

56 Change in DPOAE levels with age (75/75 db FPL)

57 10-14 yrs old 75/75 65/55 55/40

58 10-14 yrs old yrs old 75/75 65/55 55/40

59 40 SFOAE Level (db SPL) P Total at 40 db SPL P Total at 40 db SPL w/ suppressor Phase (cycles) = PSFOAE P Stimulus P SFOAE = P Total P Stimulus

60 Phase I & II: 5-yr bins starting at 10 yrs old; at least 55 in each bin N= db FPL

61 N=997; SFOAE Loss; 40 db FPL

62 N=997; SFOAE Loss; 40 db FPL 40-yr plateau

63 Change in SFOAE levels with age (40 db FPL)

64 SFOAE Total Stimulus Jitter possible source of variability.

65 After mid life changes

66 Funding: National Institutes of Health [R01 DC003552]

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69 Less reflection DP phase accumulation for older age groups.

70 Does this signify broadening cochlear tuning with age?

71 CLUES con ions

72 Behavioral Behavioral thresholds and DPOAEs show clinically significant shift as early as 25 years of age. Loss evident across a wider frequency range in DPOAEs. DPOAEs Largest shift in thresholds and DPOAEs between 30 and 49 years old. These age-related changes are visible slightly above the traditionally measured frequency range (6-12 khz for thresholds, 4-16 khz for DPOAEs).

73 DP Th 1.5 khz In the approximate middle of the cochlea (1.5 khz), DPOAE and behavioral thresholds show signs of decline with age. DP Th 12.5 khz At the cochlear base (>12.5 khz) both behavioral thresholds and DPOAEs show accelerated declines. Th Th DP DP A second faster phase of threshold decline might represent neural loss. Age related changes in DPOAEs are evident at all stimulus levels.

74 SF DP Th Global Observations Age- or life-related decline starts early, perhaps as soon as developmental changes are complete. The central nervous system is able to largely compensate for these peripheral changes for significant portions of our life span.

75 outer & middle ears dominantly cochlear, outer hair cells with others all hell breaks loose

76 Thank You NIH/NIDCD; American Hearing Research Foundation; ASHA Foundation; Deafness Research Foundation.