Sinusoidal vertical-axis rotation test in a patient with a long history of vestibular complaints.

A 38-year-old man came to the office for evaluation of a new series of episodes of dizziness. He had been a patient for 14 years, and he had an 18-year history of intermittent vestibular complaints, including disabling rotary vertigo with nausea.

The patient said he felt well "ninety percent of the time." He said he usually became dizzy when he heard loud music or rode in an elevator. He had been taking sodium fluoride and calcium carbonate; whenever he stopped taking these agents, his symptoms would return.

He had earlier been diagnosed with hypercholesterolemia and was prescribed niacin. However, the niacin also appeared to trigger dizziness; 2 weeks after he stopped taking niacin, his dizziness disappeared. He also had a 1-year history of panic attacks, during which he became nervous and anxious and felt the need to leave whatever room he was in at the time. He reported no tinnitus, hearing loss, or aural fullness. He did have a lifelong history of monocular nystagmus with either eye open.

A review of systems and the patient's personal and family history shed no light on the cause of his latest episodes. The clinical neurotologic examination revealed that the man had difficulty performing the sharpened Romberg test. He also exhibited left nuchal tenderness along with the monocular nystagmus with either eye open.

Previous electronystagmography had revealed a very brisk left-beating nystagmus in the supine and right lateral positions and an equally brisk right-beating nystagmus in the left lateral position. Earlier alternate binaural bithermal stimulation had prompted hyperactive responses to all stimuli, and the simultaneous binaural bithermal stimulation had induced a strong type 3 left-beating nystagmus.

At this latest office visit, the patient underwent the sinusoidal vertical-axis rotation test. Based on the results (figure), the patient was diagnosed with an incomplete neurologically compensated peripheral vestibular disorder.

[Graph omitted]

CALCULATIONS

Freq.  Vol.  Gain  Phase  Symmet.
 Hz    d/s         (deg)     %

0.010   60   0.49   -40    R73.6
0.020   60   0.77   -32    R61.7
0.040   60   0.83   -13    R68.5
0.080   60   0.80     4    R53.7
0.100  100   0.67    -5    R38.7
0.160   60   0.78     2    R32.1
0.320   60   0.73     5    R47.6
0.500   60   0.77    13    R31.5