Delay in the absolute latency of auditory brainstem response (ABR) component P1 in acute inflammatory demyelinating disease.

A patient with an acute inflammatory demyelinating disease and bilateral involvement of the peripheral (i.e. extracranial) portion of the VIII n. is described. The diagnosis of VIII n. involvement was made on the basis of grossly prolonged Auditory Brainstem Response (ABR) component P1 latencies which resolved to normal latencies in one year. It is suggested that involvement of the peripheral myelin is not uncommon in central demyelinating disease even in the absence of auditory system complaints.