Electronystagmography in a patient with a peripheral vestibular disorder.

A 29-year-old man had a 2-year history of dizziness. It began after he experienced a head cold. When he blew his nose, he felt a pop in his left ear, which was followed by severe dizziness and later nausea. This lasted for 2 or 3 weeks. The dizziness was so severe for a few days that he could not move in any direction, did not know which way was up, and had no equilibrium. When the dizziness was less severe, he felt pressure under both eyes and had a lightheaded feeling. He had experienced occasional lightheadedness for about 2 years before the onset of this dizziness.

When he came to the office, he was wearing a scopolamine patch, which allowed him to function normally. He took 25 mg of meclizine as needed. He had tried hydrochlorothiazide and corticosteroids without benefit. He reported no tinnitus, hearing loss, or aural fullness. His family history included hearing loss in both parents, one of whom had been diagnosed with otosclerosis. He was on a low-salt diet. A contrast-enhanced MRI was negative, and his auditory brainstem response was normal.

On electronystagmography, there was a spontaneous 6[degrees]/sec left-beating nystagmus. This nystagmus was found in all positions (supine, right and left lateral, and neck torsion). There was no evidence of a fistula sign on either electronystagmography or acoustic immittance bridge testing. The tracing was not clear in places, which indicated a possible inadequate electrode coupling. The caloric responses were corrected for the pre-existing nystagmus. The reduced vestibular response was 7%, and the directional preponderance was 20% to the right. The simultaneous binaural bithermal showed a type 2 response, with the pre-existing left-beating nystagmus reduced by 3%/sec of induced right-beating nystagmus. This revealed a reduced vestibular response left.