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auditory neuropathy spectrum disorder


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auditory neuropathy,auditory dys-synchrony

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auditory neuropathy spectrum disorder

  1. 1. AUDITORY NEUROPATHY SPECTRUM DISORDER Dr Anusree A Karun 2nd yr DLO UIORL Madras Medical College Chennai
  2. 2. 27 yr old female presented to our OPD with chief complaints of • Hard of hearing – right side *8 yrs • Vertigo *8 yrs • Tinnitus-right side * 5 yrs
  3. 3. O/E GPE- Normal ,,all pripheral nerves intact –ear –external-normal - eac ,tm- intact Tuning fork tests (R) (L) Rinne - +ve +ve Weber- lateralised to left ABC- reduced not reduced Vestibular funtion tests –normal No cerebellar signs No nystagmus Facial nerve bilateral normal
  4. 4. • PTA-bilateral mild SNHL • Pure tone average • right ear -38.3dB HL • left ear-38.3dB HL
  5. 5. Previous PTA -2015
  6. 6. PTA -2014
  7. 7. • IMPEDENCE – bilateral reflexes were absent no e/o middle ear pathology • Speech audiometry tests- Speech reception threshold- right-50dB HL left-50dB HL Speech discrimination score – right -30% left -35%
  8. 8. • OAE-bilateral OHC functional • BERA - for all five waves peaks could not be obtained at 90dB HL for click stimuli at a repetition rate of 11.1 clicks per seconds -Wave morphology & replicability was poor • CERA -prolonged latency and reduced amplitude -abnormal waves
  9. 9. ….Hearing ,feeling but never truly comprehending • Audiologic evaluation revealed …. • HEARING LOSS AND SPEECH INTELLIGIBILTY SCORES OUT OF PROPORTION TO HER PRESUMED HEARING LOSS Progressive ANSD
  10. 10. • Only treatment options left with us to address her complaints were– SPEECH ENHANCING STRATEGIES COMMUNICATION STRATEGIES ASSERTIVE TRAINING As she was not ideal for a hearing aid or implantation considering her magnitude of hearing loss
  11. 11. AUDITORY NEUROPATHY or AUDITORY DYSSYNCHRONY • Describes a diagnosis with observations of inconsistent measures of hearing, i.e. where hearing sensitivity is better than might have been expected from the acoustic brainstem evoked responses
  12. 12. • Cochlear amplification is preserved in these individuals, but discharges from the auditory nerve is asynchronous • Synchronous firing of auditory nerve fibers is important for extracting complex acoustic features such as spectral peaks and waveform envelopes for speech recognition. • The inability to follow temporal fluctuations is an important cause for poor speech perception in individuals with ANSD
  13. 13. …...characterised by  Normal outer hair cell function evidenced by normal EOAE and / or cochlear microphonics responses coupled with absent or severely abnormal ABR responses Pure tone audiogram may range from normal to profound hearing loss Elevated or absent middle ear reflexes
  14. 14. • Impaired speech discrimination scores and increased speech reception thresholds Rule out central auditory processing disorders • Binaural intergration and seperation • Monoaural low redundacy speech • Temporal resolution measurement gap in noise test amplitude modulation detection test • LLR
  15. 15. PREVALENCE • Overall prevalence rare- 1-3 children per 10,000 births • 40% in neonates with high risk for HL • 2-15% in children with known hearing loss • 1 in 10 children with hearing loss and severely abnormal BERA
  16. 16. PREVALENCE • Our data shows (study conducted in rgggh mmc ISH 2010-2012) prevalence of ANSD among sensory neural hearing impaired is not rare but accounts for 5.06% • Prevalence among children undergoing screening -0.42%
  17. 17. More common in children 50 % of all cases and 92 % of all bilateral cases manifests before 4 yrs of age Late onset ANSD –Rare incidence
  18. 18. RISK FACTORS • Neonatal history of anoxia hyperbilirubinemia mechanical ventilation • Congenital brain abnormalities • Low birth weight • Extreme Prematurity- < 28 wks • Genetic or family history of AN/AD • Also seen in association with Viral diseases , seizure disorders, high grade fever
  19. 19. ETIOLOGY • Abnormality causing AN/AD resides in the lower auditory system- specifically  damaged inner hair cells  abnormal IHC - auditory nerve synapse the spiral ganglion neurons or the axons or dendrites of the auditory nerve itself. Reduced neuronal populations in brainstem
  20. 20. • Mutation in otoferlin-most common genetic cause of non syndromic AN • Otoferlin is a calcium detector for exostosis –required for replenishment of vesicles in active regions • Absence of functional otoferlin protein selectively affects the inner hair cell synapse, resulting in profound deafness with preserved OHC function.
  21. 21. Etiology and associated conditions • A mutation(overexpression) in DIAPH3 causes nonsyndromic dominant AN- defect of inner hair cell stereocilia and loss of synapses results in this phenotype • Syndromic neuropathies– 1.Friederich ataxia(normal wave1 & middle ear auditory symptoms reflexes,indicating brainstem anomaly and not manifests first auditory nerve or IHC) occurs as a part of 2.charcot Marie tooth disease generalised neural 3.Lebers hereditary optic neuropathy deterioration 4.Stevens–johnson syndrome 5.Ehler danlos syndrome.
  22. 22. Etiology and associated conditions • Aplasia or sometimes hypoplasia of the auditory nerve with normal cochlear morphology may also lead to an AN phenotype. • Any neurotoxic environmental insult -including chemotherapeutic agents, hyperbilirubinemia- (damages brainstem cochlear nuclei, auditory nerve, superior olivary complex, lateral lemniscus, trapezoid bodies, inferior colliculus) or anoxia.
  23. 23. Treatment • Hearing normal - Speech pathology SPEECH ENHANCING STRATEGIES COMMUNICATION STRATEGIES ASSERTIVE TRAINING • Hearing aid trial for language learning • Cochlear implant when No improvement seen with HA - - helps in improving speech comprehension and language acquisition -CI provided consistent neural firing and the stimulus promotes neural survival and restore temporal activity. -Those with good temporal residual processing and normal LLR performed well • Brainstem implant-when auditory nerve is aplastic or absent
  24. 24. Our statistics COMPLAINTS PTA SRT SISI ART OAE BERA 21/f L HOH Reduced clarity of speech R Mild low frequency SNHL L moderate low frequency SNHL R-75dB L-80 dB R-18% L-8% B/L I/L &C/L -VE + AbN 2 1/2 /F Not respondng to loud sounds since birth Not done Not done Not done Not done + AbN 22/ m R Mild low frequency SNHL L minimal frequency SNHL R-50dB L-60 dB R-20% L-18% B/L I/L &C/L -VE + AbN
  25. 25. Our statistics COMPLAINTS PTA SRT SISI ART OAE BERA 14/f B/L HOH B/L Severe SNHL R-90dB L-90 dB R-80% L-85% B/L I/L &C/L -VE + AbN 25/ M B/L HOH B/L Moderate SNHL R-85dB L-85 dB R-0% L-0% B/L I/L &C/L -VE + AbN 24/ m B/L HOH R profound SNHL L severe SNHL R-70dB L-65 dB R-0% L-0% B/L I/L &C/L -VE + AbN
  26. 26. • One child benefited with cochlear implant • Majority of the remaining benefited with hearing aid • One pt with severe speech recognition difficulty but with mild hearing loss managed with speech enhancing strategies
  27. 27. • Those with good residual temporal processing particularly amplitude modulation detection seems to be associated with significant benefit from hearing aids / cochlear implant • Late onset ANSD benefits more from hearing aid as they would have had a long period of normal period of normal hearing • Those with normal LLR benefitted well with hearing aid / cochlear implants
  28. 28. • Central auditory deafness –a continuum that includes cortical deafness ,word deafness and auditory agnosia • BERA normal ,CERA abnormal –cortical deafness -primary auditory cortex of brain affected bilaterally –most commonly due to stroke-Pt aware of their deficit ,non verbal sounds identified,defective language comprehension and repition • BERA MLR LLR normal - Auditory agnosia –secondary and tertiary auditory cortex of brain(R hemisphere lesion)-Pt unaware of their deficit –inabilty to recognize non verbal sounds,preserved ability to comprehend speech ,amusia a subtype –inablity to percieve music
  29. 29. ..take home message • Neonatal screening should include BERA and not just OAE especially in high risk cases • Always consider AN/AD as a DD for SNHL in children and adults especially those with speech recognition difficulties • Clearer protocols to locate site of insult in AD/AN is lacking ,,, eg : no tests are available to asses the function of IHC • Need protocols to describe -stable AN/AD -progressive AN/AD- manifests in adolescents or early childhood -reversible AN/AD -maturational defects • Hearing aid or cochlear implant??