Sinusoidal vertical-axis rotation test in a patient with a long history of dizziness. (Vestibulology Clinic).

A 76-year-old man came to the office with a complaint of dizziness, which he had been experiencing for 30 years. He reported four episodes in which he felt as if his head was in rapid motion. These spells were followed by nausea, vomiting, and fatigue. After a few hours of sleep, he would feel perfectly well. His most recent spell of this type had occurred 10 months earlier. During the previous 4 months, he had experienced intermittent dizziness that lasted a few minutes; these spells occurred approximately twice a week. During these episodes, he felt unsteady while walking.

The patient had been wearing a hearing aid in both ears for the previous 3 years. He said his hearing was worse on the left and that during the previous 2 months, he had noted intermittent tinnitus on that side. He was not sure if the tinnitus was associated with his dizziness. He reported no aural fullness.

Electronystagmography revealed a 30% reduced vestibular response on the left and a normal value for directional preponderance. Audiology revealed a moderate flat sensorineural hearing loss on the left; his speech reception threshold was 60 dB, and his speech discrimination score was 20% at 90 dB. On acoustic immittance testing, tympanometry was normal. Acoustic reflex testing revealed a cochlear site (moreso on the left) and no reflex decay.

The sinusoidal vertical-axis rotation test (sinusoidal harmonic acceleration test) revealed the following:

Gain. Gains were low at 0.02 Hz.

Phase. Leads at 0.02 and 0.08 Hz and a lag at 0.5 Hz were consistent with a peripheral vestibular disorder.

Symmetry. Asymmetry was present on the right at 0.01, 0.02, and 0.08 Hz. This abnormality was consistent with an incompletely compensated peripheral vestibular disorder. In approximately 60% of cases, the asymmetry points to the side of the lesion. In this case, it did not.

Fixation suppression. Fixation suppression was present.

These results were consistent with the patient's history and clinical findings. They documented his ongoing inability to compensate for the peripheral vestibular disorder that was identified on electronystagmography, and they were used to monitor the patient's response to medical therapy.

[Graph omitted]

[Graph omitted]

[Graph omitted]

[Graph omitted]

CALCULATIONS

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

* 0.010   60   0.40   -55    R21.4
* 0.020   60   0.34   -41    R29.7
* 0.040   60   0.51   -19     L2.8
* 0.080   60   0.55   -13    R16.5
* 0.160   60   0.60     3     R1.5
* 0.320   60   0.70     8     L5.9
* 0.500   60   0.60    20    L10.3