Possible central vestibular findings in a patient with a peripheral vestibular disorder.

A 51-year-old man presented with a chief complaint of rotary vertigo. His symptoms had begun 1 year earlier, when be first experienced a brief spell of rotary vertigo with diaphoresis. He had gone to an emergency room, where his electrocardiogram was normal. Thereafter, he would experience a similar spell every few months; these spells occurred with a position change and while walking.

One month prior to his visit to the author's office, he said that while driving he felt like he had "fallen into a ditch."On another day he had experienced a brief period of unconsciousness. When he regained consciousness, he said he experienced a floating feeling and lightheadedness for 8 hours. Four days later, he experienced "room spinning" while lying down, then a brief"unbalanced" feeling, and finally a "woozy" feeling for as long as 1 hour. Thereafter, his spells became much more frequent; he had experienced 10 such episodes during the preceding month.

The patient had an 8-year history of hearing loss in the left ear, but his hearing had not become progressively worse and had not fluctuated. The onset of his hearing loss was accompanied by tinnitus in the left ear. The tinnitus had been constant, and its character and loudness had not changed, even during his dizzy spells. He was taking belladonna/phenobarbital and prochlorperazine. Audiology revealed a flat severe sensorineural hearing loss with a speech reception threshold of 70 dB and a speech discrimination score of 12% at 100 dB.

Electronystagmography revealed a spontaneous left-beating nystagmus of 5[degrees]/sec with elements of central dysrhythmia. There was ocular fixation suppression of the nystagmus. The alternate binaural bithermal stimulus identified a 43% reduced vestibular response (RVR) left and a 31% directional preponderance right after correction for the preexisting nystagmus. The simultaneous binaural bithermal stimulus elicited a type 2 response (RVR left) even when corrected for the preexisting nystagmus. The caloric nystagmus occurred in a dysrhythmic pattern, which is associated with central lesions. There was ocular fixation suppression of all calorically induced nystagmus. Findings on magnetic resonance imaging (MRI) with and without contrast were negative for any abnormality.

The elements of the electronystagmographic findings that suggested a possible central origin of the dizziness were (1) the left-beating nystagmus with a left ear origin and (2) the dysrhythmia of the nystagmus on positional testing and to some degree on caloric testing. The elements that argued against a central origin were the hearing loss in the left ear, the RVR left on both alternate and simultaneous binaural bithermal testing, and the negative MRI findings.

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