Auditory Evoked Potential Inconsistency in Sudden Unilateral Hearing Loss with Multiple Sclerosis.

Sudden sensorineural hearing loss is a well-recognized clinical symptom in multiple sclerosis (MS). Acute inflammatory demyelination in the cochlear nerve or more central auditory tracts may cause sudden retrocochlear hearing loss. A 28-year-old male patient who was confirmed as having MS presented with suffering from dizziness as well as ongoing right-side hearing loss. We performed audiological tests, such as pure tone audiometry (PTA), otoacoustic emission, auditory brainstem response (ABR), and auditory steady-state response (ASSR). His clinical and audiological abnormalities disappeared with steroid therapy. However, each test showed different time courses of improvement. Although the results of the PTA and ASSR tests improved in exactly 1 month after the first attack, the results of the ABR reached 3 months to return to normal. To the best of our knowledge, this is the first case report of the time difference of hearing improvement shown in PTA, ASSR, and ABR tests.