Bilateral vestibular loss and oscillopsia.

The electronystagmographic (ENG) records of 5,499 patients were reviewed so as to note the level of caloric activity. Bilateral caloric reduction or loss was found in only 1.6%. Although no diagnosis could be made with a high degree of confidence in the majority of patients, bilateral Ménière's disease and exposure to ototoxic drugs were identified most frequently. The degree of caloric reduction or loss did not correlate with the subjective symptom of oscillopsia, oscillopsia test findings or results of low frequency harmonic sinusoidal rotation tests. In a few patients with bilateral caloric loss, no oscillopsia was demonstrated. Many mechanisms other than the vestibulo-ocular reflex exist to provide visual stability, and we assume these become effective in some patients with bilateral caloric reduction or loss.