Electronystagmography: Frequently overlooked significant findings. (Vestibulology Clinic).

A 48-year-old woman came to the office with an 8-month history of dizziness. The dizziness had begun as a brief rotary vertigo that lasted a few minutes and that was accompanied by numbness on the left side of her face. In time, the patient also had begun to experience light-headedness and numbness in her lower body. She had undergone an evaluation for her condition, which had included a lumbar puncture. Following the puncture, she experienced a 7-day period of rotary vertigo. Afterward, she continued to experience dizziness when changing positions and while in motion. She eventually became confined to bed for 2 weeks, and she later underwent nutritional therapy, chiropractic therapy, and vestibular rehabilitation. But then her symptoms abated to a point where she would experience entire days free of symptoms. However, on days when she woke up with a feeling of unnatural motion, she would be dizzy all day. She felt worst when she was in shopping malls and when she was fatigued. Her dizziness also became exace rbated when she turned to the left while standing and when she turned over in bed.

At the author's office, the patient denied subjective hearing loss. She said that tinnitus had been present around the time of the lumbar puncture. She characterized her tinnitus as a high-pitched humming sound that was present intermittently in either ear, but more frequently in the right. She also noted that intermittent aural fullness had been present for the previous 2 months. Like the tinnitus, it occurred in both ears, but more often in the right. However, the fullness and the tinnitus were not correlated.

A clinical neurotologic examination yielded a few positive findings, including diplacusis with the 2-kHz tuning fork and difficulty performing the sharpened tandem Romberg's test. The patient produced previously performed tests. Although audiometry revealed that the patient's hearing was normal, close examination of the acoustic immittance results showed a borderline shallow tympanometry in both ears and a negative deflection of the ipsilateral acoustic stapedial reflexes on the right. Electronystagmography showed a markedly reduced response to warm stimulus in the right ear, which led to a 37% directional preponderance. Sinusoidal vertical-axis rotation testing elicited normal gains and phases but abnormal symmetry to the right at two frequencies.

Six months later, the patient underwent follow-up testing. While her hearing was still in the normal range, it had declined slightly since her previous examination, more so in the right ear. One finding on tympanometry was a near-shallow or stiff curve on the right. Acoustic stapedial reflexes were absent in both ears at 0.5 kHz. The simultaneous binaural bithermal test elicited a type 1 response.

On metabolic evaluation, the patient's glucose tolerance test results were flat and her serum insulin levels were elevated. Findings on ultrathin computed tomography of the temporal bones were consistent with otosclerosis of the labyrinthine capsule, which was more pronounced on the right. She was placed on a diet to address her metabolic factors and prescribed the bisphosphonate etidronate and calcium to address her otosclerosis.

When the patient returned 3 months later, she reported improvement. Although her dizziness was still present intermittently, its severity and duration were much less pronounced. She reported less tinnitus and less aural fullness. Her regimen was continued.

When the patient returned in 4 months, she reported continued improvement. Her spontaneous spells of dizziness were less common, and periods when she felt no dizziness were more frequent and longer lasting. Her tinnitus and aural fullness were much less pronounced, and the numbness in her face had disappeared. She was switched to a different bisphosphonate (risedronate), and sodium fluoride was added to her regimen.

The patient returned 3 months later and reported that her dizziness was 95% resolved. Her tinnitus occurred very seldomly, and her aural fullness had disappeared. Seven months later, the dizziness was completely gone.

A number of findings in this case should be highlighted. One significant finding was the directional preponderance of the alternate binaural bithermal caloric stimulus in a patient with her history. The second important finding was the abnormal symmetry on sinusoidal vertical-axis rotation testing, which provided additional objective findings consistent with her symptoms. Third, the simultaneous binaural bithermal test played no significant diagnostic role in this case, which is unusual. Fourth, a flat glucose tolerance test result is considered by most endocrinologists to be a variant of normal, but in this patient, the glucose level played a significant role in her symptoms. Finally, the acoustic immittance findings, warm-water caloric response, and clinical symptoms were all consistent with the imaging findings.

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From Neurotologic Associates, P.C., New York City.