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Sarah Creeke sarah.creeke@nhs.net

Severe-Profound Hearing Loss Study Day 12 December 2013. Special considerations How much should we investigate and allow for dead regions and what about frequency compression?. Sarah Creeke sarah.creeke@nhs.net. Overview. What is a “cochlear dead region”? Clinical testing

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Sarah Creeke sarah.creeke@nhs.net

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  1. Severe-Profound Hearing Loss Study Day 12 December 2013 Special considerationsHow much should we investigate and allow for dead regions and what about frequency compression? Sarah Creeke sarah.creeke@nhs.net

  2. Overview • What is a “cochlear dead region”? • Clinical testing • Prevalence of dead regions • Relevance to hearing aid settings • Whom should we test? • Case studies • Frequency compression and dead regions

  3. Cochlear dead region (DR) No functioning IHCs and/or no functioning neurons Described by the range of characteristic frequencies where IHC/neuron function is lost Edge frequency (fe)

  4. Loss of inner hair cells • Less efficient stimulation of the auditory nerve • Elevated thresholds • “Noisy transmission” inner hair cells (IHCs) outer hair cells (OHCs)

  5. Off-frequency listening High level tone within the dead region is detected (less efficiently) by an adjacent area of the cochlea tuned to a different frequency Basilar membrane displacement Threshold fe Cochlear dead region

  6. Why assess for off-frequency listening? • Reason for poor speech discrimination or perceived distortion • counsel expectations • more emphasis on assistive listening devices • May affect • hearing aid settings • decision to aid • choice of aid • May influence decision to refer for cochlear implant (CI) assessment

  7. DRs reduce speech recognition • Listeners with DRs had poorer sentence understanding in noise and poorer subjective hearing aid performance in reverberation or noise than listeners without DRs (Preminger et al., 2005) • In high noise, scores for listeners with DRs plateaued with increasing bandwidth, but matched subjects with no DRs continued to improve (Mackersieet al., 2004) • no difference in quiet and low noise

  8. Threshold Equalising Noise (TEN) test • TEN test is fastest for clinicaldetection of dead regions (DRs) • set-up and instruction • 1 min/frequency/ear • Measures the threshold of a puretone in the presence of a speciallydesigned broadband masking noise (TEN) • abnormally raised threshold gives a positive result • Easiest to use TEN(HL) version (Moore et al., 2004)

  9. Equipment for a TEN test • 2 channel audiometer with TDH 39, 49 or 50 or ER-3A earphones • CD player and TEN(HL) CD (unless built in) • Different CD for ER-3A (Moore et al., 2012)

  10. TEN test: audiometer connections Output Ext A Left CD player External inputs Ext B Right Audiometer Ch1 (Ext B) Ch2 (Ext A)

  11. TEN test: audiometer settings • TEN(HL) CD Left channel: tone Right channel: TEN(HL) • Audiometer settings • both channels on external input • direct both channels to same ear (ipsilateral) • 2 dB step size • Play Track 1 and adjust to 0 dB on both VU meters

  12. TEN test: procedure • Measure not-masked threshold in 2 dB steps using tone from CD (unless TEN test built-in) • Apply ipsilateral TEN • level on dial at least 10 dB above not-masked threshold • reinstruct to ignore masking noise/warn of loudness discomfort • turn up the masker level gradually • measure masked threshold

  13. How to set the TEN level • For frequencies where the hearing loss is less than or equal to 60 dB, set the TEN level to 70 dB. • When the hearing loss is 70 dB or more at a given frequency, set the TEN level 10 dB above the audiometric threshold at that frequency. For example, if the audiometric threshold is 75 dB HL, set the TEN level to 85 dB HL. • If the TEN is found to be unpleasantly loud, or if the maximum TEN level of 90 dB HL is reached, then the TEN level can be set equal to the audiometric threshold. This should still give a definitive result. Moore (2009): White paper for Interacoustics

  14. TEN test: criteria for a dead region • Masked threshold 10 dB or more above level of TEN and • Masked threshold at least 10 dB above not-masked threshold If masked threshold is raised but < 10 dB above TEN, increase level of TEN and retest

  15. * Non-standard methodology/criteria

  16. Severe-profound clinic Bird (2010)

  17. Implications for hearing aid gain • High-frequency DRs tested using low pass filtered stimuli • performance plateaus or worsens as amplification extends into the DR (Vickers, Moore & Baer, 2001; Baer et al., 2002) • listeners with high-frequency DRs can extract useful information up to about one octave inside the DR • High-frequency dead regions • reduce gain > 1.7 x edge frequency

  18. Case study (1): hearing aid gain TEN test results • 500 Hz – normal • 750 Hz – raised thresholds (take as “edge frequency”) • 1 kHz – could not test Hearing aids • 1.7 x 750 Hz = 1.3 kHz • Reduce gain at freqs >1.3kHz • Can fit less powerful, smaller aid

  19. Hearing aid trial with DRs Cox et al.(2012) • Compared NAL-NL1 (NAL) and low-pass filtered (LP) hearing aid settings for mild to moderately severe HL • high frequency reduction not tailored to fe • Fitted unilaterally • Subjects with and without DRs • some “patchy”, not continuous DRs

  20. Hearing aid trial comparing NAL and LP Cox et al.(2012) findings: • Speech recognition in quiet was better for NAL in subjects with DRs and without DRs • Speech recognition in noise was better for NAL for subjects without DRs; performance was equivalent for NAL and LP for subjects with DRs • Both groups rated NAL more highly for subjective speech understanding in daily life • 1/3 subjects preferred LP program • Recommended not reducing gain based on DRs at one or two test frequencies

  21. Low-frequency DRs • Low frequency dead regions • reduce gain < 0.57 x edge frequency (Vinay and Moore, 2007b; Vinay et al., 2008) • But be flexible based on the listener’s preferences!

  22. Whom to test? • Routine in severe-profound hearing loss clinic • Steep slopes • more likely to have DRs, but slope is not a predictor(Aazh and Moore, 2007) • Unexpectedly poor speech discrimination • Complaints of distortion

  23. Severe-profound HL • High prevalence of DRs • Many losses too severe to test • Which results are clinically significant? Counselling Hearing aid gain DRs at ≤ 2 kHz → reduce gain Clear indications of no DRs, indeterminate or patchy DRs → full bandwidth

  24. Which frequencies to test? • Start where off-frequency listening not suspected for practice • Anything that might affect hearing aid settings • Other frequencies for counselling

  25. Potential pathologies in positive results • Cochlear dead regions • Retrocochlear lesions • Ménière’s disease • Auditory neuropathy • (Vinay and Moore, 2007c) • Central auditory system All associated with poor speech discrimination, particularly in noise

  26. Case study (2): distorted hearing History • Aided in L ear Problems • Aware of increasing distortion on L TEN test • L: negative at all test freqs Outcomes • Fine tune with REMs • aiming to provide optimum gain across full aid bandwidth

  27. Case study (3): CI referral Age 79 History • HL and tinnitus for 30 years • Living alone, socially isolated • Bilateral hearing aids Clinical • IHR sentences 4/45 • TEN test R 0.5 – 3kHz L 0.5 – 2kHz Outcomes • Outside NICE guidelines for CI • Implanted after decision on special funding • Can now use a telephone • Tinnitus more troublesome

  28. Case study (4): CI referral No speech recognition. Lip-reading wife TEN test positive for DRs at all test frequencies Successfully implanted

  29. Case study (5): Progression Small drop in thresholds between 2008 and 2013 Complaining of progressive difficulties, especially in noise and on the telephone

  30. Case study (5): Progression 2004 TEN test +ve at freqs above 2 kHz in both ears 2008 TEN test +ve R: 2 kHz L: 3 kHz 2013 TEN test +ve for: R: 2, 4 kHz L: 1.5, 3, 4 kHz (not at 2 kHz) • Management focussing on hearing aid accessories (Bluetooth link to phones, radio mic), counselling and directional settings

  31. Case study (6): frequency compression High frequency dead regions • R: fe = 2 kHz • L: fe = 2.4 kHz Hearing aids • Long history of feedback problems and earmould discomfort Reduce gain above: • R: 3.4 kHz • L: 4.0 kHz Fitted with bilateral Phonak aids • Frequency compression • Open fit

  32. Case study (6): frequency compression Default settings

  33. Frequency lowering in commercial aids Phonak SoundRecover (non-linear) Frequency compression Siemens FCo micon Linear frequency transposition Widex Audibility Extender Spectral envelope warping Starkey Spectral iQ

  34. Frequency lowering and S-P HL • High-frequency gain is often limited by hearing aids • power • feedback • Frequency lowering can improve audibility • May increase distortion • trade-off 0.125 0.25 0.5 1 2 4 8 kHz

  35. Frequency compression (FC) • Phonak – non-linear frequency compression • 1.5 kHz is lowest starting frequency • low frequency speech spectrum unaltered • FC reduces spacing between harmonics, modifies spectral shape • Siemens – freq compression strategy not specified Frequency

  36. Frequency transposition • Widex – linear frequency transposition down 1 octave • filters a band around the dominant high-frequency (HF) spectral peak when intense HF energy is present • moves and overlaps HF band with lower-frequency spectrum • source and target frequencies vary, depending on input Frequency

  37. “Spectral iQ” (spectral envelope warping) • Starkey – additional spectral feature • identifies HF spectral features: /s/, /sh/ • preserves HF spectrum • generates additional spectral cue at low frequency • claims to preserve spectral cues and harmonic relationships Frequency

  38. Research with severe-profound HL • See review of peer-reviewed studies on frequency lowering: • Simpson (2009) • Alexander (2013): summary of modern frequency lowering technologies (majority on frequency compression) • Improvements mainly in recognition of fricatives and affricates • Little evidence for benefit in speech in noise • Wolfe et al.(2011) found children’s sentence recognition in noise improved with non-linear frequency compression at 6 month follow up (but no control for maturation) • Considerable individual variation in outcomes and preferences

  39. Frequency lowering and DRs • Very little published data • Only a few studies have tested for presence of DRs • Robinson, Baer & Moore (2007) tested custom frequency transposition on subjects with HF DRs • a frequency band in the DR (2fe - 2.7fe) was transposed into fe - 1.7fe and overlapped with speech low-pass filtered at 1.7fe • transposition was conditional on the presence of significant energy at HF • improved perception of affricates and /s/, /z/

  40. Hearing aid trials with DRs and frequency lowering • Robinson et al. (2009) tested frequency transposition in a wearable hearing aid • 5 subjects wore aids for 5 weeks • compared transposed and control conditions • no benefit for transposition even after experience • On-going research comparing frequency compression and transposition for listeners with DRs

  41. Conclusions • Targetted testing for cochlear dead regions is • clinically useful • possible, even in a busy clinic • If no definite indications of a dead region, initially aim for full bandwidth amplification • balance audibility against potential distortion • Optimum settings for frequency lowering yet to be determined .........

  42. References (1) • Aazh, H. & Moore, B.C.J. 2007. Dead regions in the cochlea at 4 kHz in elderly adults: relation to absolute threshold, steepness of audiogram, and pure-tone average. J Am AcadAudiol, 18, 97-106. • Baer, T., Moore, B.C.J. & Kluk, K. 2002. Effects of low pass filtering on the intelligibility of speech in noise for people with and without dead regions at high frequencies. J AcoustSoc Am, 112(3) Pt 1, 1133-44. • Bird, J. 2010. Optimisation of Service Provision for Adults with Severe and Profound Hearing Loss. Cochlear Implants International, 11, 37-42. • Cairns, S., Frith, R., Munro, K.J. & Moore, B.C. 2007. Repeatability of the TEN(HL) test for detecting cochlear dead regions. International Journal of Audiology, 46, 575-84. • Cox, R.M., Alexander, G.C., Johnson, J. & Rivera, I. 2011. Cochlear dead regions in typical hearing aid candidates: prevalence and implications for use of high-frequency speech cues. Ear Hear, 32, 339-48.

  43. References (2) • Cox, R.M., Johnson, J.A. & Alexander, G.C. 2012. Implications of high-frequency cochlear dead regions for fitting hearing aids to adults with mild to moderately severe hearing loss. Ear Hear, 33, 573-587. • Mackersie, C.L., Crocker, T.L. & Davis, R.A. 2004. Limiting high-frequency hearing aid gain in listeners with and without suspected cochlear dead regions. J Am AcadAudiol, 15, 498-507. • Moore, B.C.J., Creeke, S., Glasberg, B.R., Stone, M.A. & Sek, A. 2012. A Version of the TEN Test for Use With ER-3A Insert Earphones. Ear Hear, 33, 554-557. • Moore, B.C.J., Glasberg, B.R. & Stone, M.A. 2004. New version of the TEN test with calibrations in dB HL. Ear Hear, 25, 478-87. • Moore, B.C., Killen, T. & Munro, K.J. 2003. Application of the TEN test to hearing-impaired teenagers with severe-to-profound hearing loss. International Journal of Audiology, 42, 465-74. • Moore, B.C.J., & Malicka, A.N. (2013). "Cochlear Dead Regions in Adults and Children: Diagnosis and Clinical Implications," Semin Hear, 34, 037-050.

  44. References (3) • Preminger, J.E., Carpenter, R. & Ziegler, C.H. 2005. A clinical perspective on cochlear dead regions: intelligibility of speech and subjective hearing aid benefit. J Am AcadAudiol, 16, 600-13. • Vickers, D.A., Moore, B.C.J. & Baer, T. 2001. Effects of low-pass filtering on the intelligibility of speech in quiet for people with and without dead regions at high frequencies. J AcoustSoc Am, 110, 1164-75. • Vinay, Baer, T. & Moore, B.C.J. 2008. Speech recognition in noise as a function of highpass-filter cutoff frequency for people with and without low-frequency cochlear dead regions. J AcoustSoc Am, 123, 606-9. • Vinay & Moore, B.C.J. 2007a. Prevalence of dead regions in subjects with sensorineural hearing loss. Ear Hear, 28, 231-41. • Vinay & Moore, B.C.J. 2007b. Speech recognition as a function of high-pass filter cutoff frequency for people with and without low-frequency cochlear dead regions. J AcoustSoc Am, 122, 542-53. • Vinay & Moore, B.C.J. 2007c. TEN(HL)-test results and psychophysical tuning curves for subjects with auditory neuropathy. Int J Audiol, 46, 39-46.

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