NEURO-OTOLOGIC FUNCTION IN X-LINKED HEARING-LOSS - A MULTIPEDIGREE ASSESSMENT AND CORRELATION WITH OTHER CLINICAL-PARAMETERS

Auditory and vestibular investigations were carried out in 19 affected men and 13 obligate female carriers of 7 pedigrees with nonsyndromic hearing loss segregating as an X-linked trait. In addition, high resol ution computerised tomographic scanning was carried out in 24 affected males and 12 obligate female carriers. The neuro-otological results c onfirm that non syndromic X-linked hearing loss is a clinically hetero geneous condition, but radiological assessment of the cochlea revealed two distinct groups: a normal group, and an abnormal group characteri sed by a bulbous internal auditory meatus, a dilated facial nerve cana l and incomplete separation of the basal coil of the cochlea from the internal auditory meatus. Within a given pedigree there was marked con sistency of the presence or absence of the CT scan abnormality in the affected males. One third of the obligate female carriers of the radio logically abnormal pedigrees were shown to have a similar abnormal fin ding, but as two thirds were normal, cardiological examination did not predict carrier status. In the affected men, pure tone audiometric da ta did not correlate with the radiological abnormality, whereas vestib ular function was strikingly correlated, being normal in all but one c ase in pedigrees with normal radiology and absent, or grossly impaired , in the pedigrees with abnormal radiology. Neuro-otological abnormali ties were documented in approximately two thirds of the obligate femal e carriers, but were insufficiently frequent in occurrence or specific in type to be of predictive value.