Influence of myelography on the developmental curve of auditory brainstem responses and hearing loss.

Auditory threshold and auditory brainstem response studies were conducted in 50 patients before and after myelography. Analysis of amplitudes and latencies of auditory brainstem measurements demonstrated significant disorders of function of the cochlea and auditory pathway. The Jewett I wave showed a prolongation of latency from 1.92 to 1.98 ms using an average of all repetition rates. The Jewett III wave showed prolongation from 4.01 to 4.14 ms and the Jewett V wave prolongation from 6.01 to 6.16 ms. At the same time average amplitudes for Jewett III and V decreased. In most of the patients these disorders of function were found to be subclinical. However, 12 patients had changes ranging from a subjectively slight hearing loss to an audiometrically defined acute hearing loss. The reasons for these disorders could not be clarified. An open cochlear aqueduct through which perilymph can enter the subarachnoid space, leading to secondary endolymphatic hydrops, was suggested as the cause for the losses found. Changes in brainstem audiometry were also explained by changes in osmolality of inner ear fluids, leading to the development of an endolymphatic hydrops.