ABSTRACT
Genetic and auditory studies of 731 children with severe-to-profound hearing loss in US schools for the deaf and 46 additional children receiving clinical services for hearing loss ranging from moderate to profound demonstrated that mutations in the connexin 26 (GJB2) and connexin 30 (GJB6) genes explain at least 12% of those with nonsyndromic sensorineural deafness. Otoacoustic emissions (OAEs) testing to detect functional outer hair cells indicated that 76 of the children had emissions and therefore may have (as yet unconfirmed) auditory neuropathy/dys-synchrony (AN/AD). Five of these children with OAEs were GJB2 homozygotes or compound heterozygotes with the genotypes 35delG/35delG, W77X/W77X, 35delG/360delGAG, 35delG/V95M, and V84M/M34T. In particular, unilateral AN/AD was confirmed in a child with moderate hearing loss and the 35delG/V95M genotype. Detecting OAEs in individuals with GJB2 mutations suggests that lack of functional gap junctions as a result of GJB2 mutations does not necessarily destroy all outer hair cell function.
Subject(s)
Connexins/genetics , Hearing Loss/genetics , Adolescent , Child , Cochlear Nerve/pathology , Connexin 26 , Connexin 30 , Evoked Potentials, Auditory, Brain Stem , Hearing Loss/etiology , Hearing Loss, Sensorineural/genetics , Humans , Otoacoustic Emissions, Spontaneous , Vestibulocochlear Nerve Diseases/complicationsABSTRACT
Auditory brainstem responses (ABRs) and otoacoustic emissions (OAEs) are objective measures of auditory function, but are not hearing tests. Normal OAEs reflect normal cochlear outer hair cell function, and an ABR indicates a synchronous neural response. It is quite possible for a patient to have normal OAEs but absent or grossly abnormal ABR and a behavioral audiogram that is inconsistent with either test. These patients, who may constitute as much as 10% of the diagnosed deaf population, have auditory neuropathy/dys-synchrony (AN/AD). To diagnose AN/AD accurately, ABRs are obtained in response to condensation and rarefaction clicks to distinguish cochlear microphonics (CM) from neural responses. Appropriate management is confounded by variation among patients and changes in auditory function in some patients over time. Recommendations for management include visual language exposure through methods such as American Sign Language (ASL), Cued Speech, or baby signs, and closely following patients.
Subject(s)
Hearing Loss, Sensorineural/diagnosis , Hearing Tests/methods , Vestibulocochlear Nerve Diseases/diagnosis , Acoustic Impedance Tests , Adolescent , Adult , Audiometry, Speech , Brain Stem/physiopathology , Child , Child, Preschool , Cochlear Microphonic Potentials/physiology , Cochlear Nerve/physiopathology , Evoked Potentials, Auditory, Brain Stem/physiology , Follow-Up Studies , Hearing Loss, Sensorineural/physiopathology , Hearing Loss, Sensorineural/rehabilitation , Humans , Infant , Mass Screening , Otoacoustic Emissions, Spontaneous/physiology , Reflex, Abnormal/physiology , Vestibulocochlear Nerve Diseases/physiopathology , Vestibulocochlear Nerve Diseases/rehabilitationABSTRACT
Suppression of transient-evoked otoacoustic emissions was recorded from 29 members of the Louisiana Philharmonic Orchestra and 28 non-musician control subjects matched for age and gender. Binaural broad band noise was used as the suppressor stimulus in a forward masking paradigm. Results showed musicians to have significantly more suppression than non-musicians for both the right and left ears. Two possible explanations for this functional difference between groups are that moderately loud music serves as a sound conditioning stimulus and that music can be a mechanism for strengthening central auditory pathways which may influence the olivocochlear reflex arc. Possible explanations for this are discussed and ear, gender, and age differences within each group are examined. Additionally, middle-ear muscle reflex thresholds were found to be higher in musicians than non-musicians at some frequencies in some conditions.
