Otology Seminar--Auditory neuropathy R3 陳俊男 95/08/08 1. History: Davis and Hirsh (1979), Worthington and Peters (1980), Lenhardt (1981), Hildesheimer et al (1985): paradoxical absence of ABR and only a slight impairment of hearing but in whom cochlear microphonic or OAE had not been recorded. Incidence: Davis and Hirsh (1979): 1/200 (0.5%) Kraus et al (1984): 1.8% Hildesheimer et al (1985): 1.9% Berlin et al (2001): 10% of diagnosed deaf patient Until 2001, 70 case reports were listed as table 1. Symptoms: Difficulty understanding speech, particularly in the presence of noise Normal or near-normal hearing sensitivity but with reduced auditory perceptual or speech processing skills Synonym: Auditory neuropathy (AN), auditory dyssynchrony (AD) Etiology: 1. Genetic: mutations in several genes (MPZ, NDRG1, and PMP22) critical for periphaeral nerve myelination and axonal survival (Chapon et al. 1999; De 2. 3. 4. 5. Jonghe et al. 19999; Kalaydjieva et al. 2000; Maier et al. 2003) Infectious (measles, mumps) Metabolic (diabetes, hypoxia) Congenital (atresia) Neoplastic (tumors) 2. Diagnostic criteria: Starr (1996): A group of patients with hearing deficits who had preserved OAE and severely abnormal ABR…, complained of difficulty understanding speech, particularly in the presence of noise… 1. Understanding of speech worse than predicted from the degree of hearing loss on their behavioral audiograms 2. Recordable otoacoustic emissions and/or cochlear microphonic, 3. Absent or atypical auditory brain stem response 4. Hearing loss of variable severity and configuration Primary auditory neuropathy (13): auditory dysfunction without no concomitant neurological deficit on a detailed examination. Familial auditory neuropathy (3): Nonsyndromic heterditary AN, X-linked recessive and autosomal recessive hereditary pattern Associated with peripheral neurologic lesions: up to 80% Adult Friedreich’s cerebellar ataxia: genetic disorder characterised by a progressive degeneration of the spino-cerebellar system due to an abnormality of a gene on chromosome 9 (called Frataxin). Charcot-Marie-Tooth disease: hereditary motor and sensory neuropathy (HMSN) or peroneal muscular atrophy, comprises a group of disorders caused by mutations in genes that affect the normal function of the peripheral nerves. Type 1, which affects the myelin sheath Type 2, which affects the nerve fibers (also called axons) themselves Neonatal Hyperbilirubinemia 3. Auditory pathway: Inner hair cell Type I spiral ganglia cells cochlear nucleus (ponto-medullary junction) Most, contralateral superior olivary nucleus (upper pons) Inferior colliculus (midbrain) Medial geniculate ganglia (thalamus) Cortex (temporal lobe) Superior olive (efferent olivo-cochlear bundle, OCB) Outer hair cells of both cochleas, larger contralateral than ipsilateral projection (Suppress OHCs activity) Spiral ganglion ipsilateral and contra-lateral facial nuclei stapedius muscle (middle ear muscle reflex, MEMR) Tactile MEMR: tensor tympani response, via trigeminal nerve 4. Specific locations of dysfunction: 5. Mechanism of “Neuropathy” 1. Demyelinating neuropathies Hallmark: slowed or blocked nerve conduction produces motor or sensory (or both) symptoms distal to the site of demyelination 1. Segmental (localized) demyelination: ex. Nerve compression (acoustic neuroma) 2. Autoimmune: ex. Guillain-Barre syndrome) 2. Axonal neuropathies Hallmark: dying back of the most distal portion of peripheral nerves because of inadequate axonal transport, in one or both directions, of subcellular organelles and critical metabolic substrates and growth factors between the neuronal cell body and distal portion of its axon 3. Mixed neuropathies 6. Perceptual consequences of disrupted of disrupted auditory nerve activity Character of AN: 1. No significant difficulty in performing pure-tone intensity discrimination 2. Impairment in pitch discrimination at low frequencies (<4000 Hz) but not at high frequencies (>4000 Hz) 3. Temporal processing a. b. c. d. Difficulty detecting short sounds but not long sounds Difficulty in gap detection even at comfortable loudness levels Difficulty in detecting both slow and fast temporal modulations Cannot effectively separate sounds occurring successively e. f. g. h. Difficulty in detecting signals in noise Can use the interaural level difference cue to localize sound Cannot use the interaural time difference cue to localize sound Can follow slow temporal fluctuation (3 Hz) to perceive monaural beats but cannot follow fast fluctuation (500 and 503 Hz) to perceive binaural beats 4. Possible models of AN 7. Management: 1. Audiologic (incorporation of screening ABR) and medical monitoring of infants considered to be at risk for “auditory neuropathy”—intensive neonatal care, family history of hearing loss, hyperbilirubinemia 2. Spontaneous recovery or no obvious symptoms of an absent ABR 7-10% of the AN/AD patients we have seen have had no observable symptoms other than an absent ABR, or have developed normal speech and language with only complaints of mild difficulty in language learning or poor hearing in noise. Not to manage the child as deaf until those tests show absent emissions of absent reflexes 3. Amplification Patient with AN have cochlear functionHearing aids are not recommended Powerful hearing aids may destroy outer hair cell function and preventable high frequency sensory loss 4. FM system in classroom 5. Sign language: ex. American Sign Language (ASL) 6. Cochlear implantation: All children with hearing loss in the severe-to-profound range who do not benefit from conventional amplification can be considered candidates for a CI Other indication: OAEs, CM and ABR are absent and electrical stimulation of the promontory elicits a CAP (Spiral ganglion cells are alive) Pre-CI Post-CI Comparison post-CT benefit between AN and cochlear hearing loss: 1. Ling Six Sounds Test (Ling, 1978): Assess patient’s ability to either detect or discriminate the phonemes/a, u, I, s, sh, m/ when presented auditory only (i.e., no visual cues) # correct/30 2. Early Speech Perception (ESP) test (Moog and Geers, 1990): Assess speech perception ability 1=no pattern perception, 2=pattern perception, 3=some word identification, 4=consistent word identification 3. Test of Auditory Comprehension (TAC) (Trammell and Owens, 1977): suprasegmental discrimination, memory-sequencing abilities for up to four critical elements, auditory comprehension, and auditory figure-ground abilities . 8. Further study: 1. Definite pathological site of AN 2. More sensitive screening protocol for neonatal babies, especially high risk 3. Vestibular neuropathy? 4. Effective treatment? Cochlear implantation? 9. Reference: 1. Starr A, Picton TW, Sininger Y, Hood LJ, Berlin CI., Auditory neuropathy. Brain. 1996 Jun;119 ( Pt 3):741-53. 2. Berlin CI, Morlet T, Hood LJ., Auditory neuropathy/dyssynchrony: its diagnosis and management. Pediatr Clin North Am. 2003 Apr;50(2):331-40, vii-viii. 3. Wang Q, Gu R, Han D, Yang W. Familial auditory neuropathy. Laryngoscope. 2003 Sep;113(9):1623-9. "Auditory neuropathy": physiologic and pathologic evidence calls for more diagnostic specificity. Int J Pediatr Otorhinolaryngol. 2003 Jul;67(7):707-28. 4. Rapin I, Gravel J. Review. 5. Katada A, Nonaka S, Harabuchi Y. Cochlear implantation in an adult patient with auditory neuropathy. Eur Arch Otorhinolaryngol. 2005 Jun;262(6):449-52. Epub 2004 Nov 12. 6. Loundon N, Marcolla A, Roux I, Rouillon I, Denoyelle F, Feldmann D, Marlin S, Garabedian EN. Auditory neuropathy or endocochlear hearing loss? Otol Neurotol. 2005 Jul;26(4):748-54. 7. Zeng FG, Kong YY, Michalewski HJ, Starr A. Perceptual consequences of disrupted auditory nerve activity. J Neurophysiol. 2005 Jun;93(6):3050-63. Epub 2004 Dec 22. 8. Berlin CI, Hood L, Morlet T, Rose K, Brashears S. Auditory neuropathy/dys-synchrony: diagnosis and management. Ment Retard Dev Disabil Res Rev. 2003;9(4):225-31. 9. Mason JC, De Michele A, Stevens C, Ruth RA, Hashisaki GT. Cochlear implantation in patients with auditory neuropathy of varied etiologies. Laryngoscope. 2003 Jan;113(1):45-9. 10. Sheykholeslami K, Schmerber S, Habiby Kermany M, Kaga K. Sacculo-collic pathway dysfunction accompanying auditory neuropathy. Acta Otolaryngol. 2005 Jul;125(7):786-91. 11. Trautwein PG, Sininger YS, Nelson R. Cochlear implantation of auditory neuropathy. J Am Acad Audiol. 2000 Jun;11(6):309-15. 12. Starr A, Sininger Y, Nguyen T, Michalewski HJ, Oba S, Abdala C. Cochlear receptor (microphonic and summating potentials, otoacoustic emissions) and auditory pathway (auditory brain stem potentials) activity in auditory neuropathy. Ear Hear. 2001 Apr;22(2):91-9. 13. Shivashankar N, Satishchandra P, Shashikala HR, Gore M. Primary auditory neuropathy - an enigma. Acta Neurol Scand. 2003 Aug;108(2):130-5. 14. Brown DK, Dort JC. Auditory neuropathy: when test results conflict. J Otolaryngol. 2001 Feb;30(1):46-51.