title: Mutation of OPA1 gene causes deafness by affecting function of auditory nerve terminals.
abstract: Autosomal dominant optic atrophy (DOA) is a retinal neuronal degenerative disease characterized by a progressive bilateral visual loss. We report on two affected members of a family with dominantly inherited neuropathy of both optic and auditory nerves expressed by impaired visual acuity, moderate pure tone hearing loss, and marked loss of speech perception. We investigated cochlear abnormalities accompanying the hearing loss and the effects of cochlear implantation. We sequenced OPA1 gene and recorded cochlear receptor and neural potentials before cochlear implantation. Genetic analysis identified R445H mutation in OPA1 gene. Audiological studies showed preserved cochlear receptor outer hair cell activities (otoacoustic emissions) and absent or abnormally delayed auditory brainstem responses (ABRs). Trans-tympanic electrocochleography (ECochG) showed prolonged low amplitude negative potentials without auditory nerve compound action potentials. The latency of onset of the cochlear potentials was within the normal range found for inner hair cell summating receptor potentials. The duration of the negative potential was reduced to normal during rapid stimulation consistent with adaptation of neural sources generating prolonged cochlear potentials. Both subjects had cochlear implants placed with restoration of hearing thresholds, speech perception, and synchronous activity in auditory brainstem pathways. The results suggest that deafness accompanying this OPA1 mutation is due to altered function of terminal unmyelinated portions of auditory nerve. Electrical stimulation of the cochlea activated proximal myelinated portions of auditory nerve to restore hearing.
authors.affiliation: Department of Pediatrics, University of California, Irvine, CA, USA.
authors.forename: Taosheng
authors.initials: T
authors.lastname: Huang
authors.forename: Rosamaria
authors.initials: R
authors.lastname: Santarelli
authors.forename: Arnold
authors.initials: A
authors.lastname: Starr
mesh_terms: D000161:Acoustic Stimulation; D000200:Action Potentials / Q000502:physiology; D000328:Adult; D001300:Audiometry, Evoked Response; D001301:Audiometry, Pure-Tone; D001306:Auditory Pathways / Q000503:physiopathology; D001307:Auditory Perception / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology; D002648:Child; D003051:Cochlea / Q000503:physiopathology*; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000503:physiopathology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000235:genetics* / Q000502:physiology; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics*; D005838:Genotype; D034381:Hearing Loss / Q000235:genetics* / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D009901:Optic Nerve Diseases / Q000235:genetics
chemical_list: D020558:GTP Phosphohydrolases; C415198:OPA1 protein, human