Bilateral idiopathic loss of peripheral vestibular function with normal hearing

From 1982 to 1993, 52 electronystagmograms (FNG) revealed an absent nystagmic reaction on both caloric (44 30 and 10 degrees C water irrigation) and rotatory pendular testing (0.05 Hz/peak velocity 60 degrees/s), which represents 0.6% of all FNG performed during this period. Among these examinations, 14 patients (27%) presented a bilateral idiopathic loss of vestibular function (BILVF) with normal hearing and without associated neurological symptoms. Two different groups emerged: one group with simultaneous onset of BILVF ( 10 patients), with sudden imbalance and disequilibrium, worse in darkness, with an absence of bilateral caloric and pendular response. The other group (4 patients) was characterized by sequential onset of BILVF. These patients experienced several episodes of acute vertigo with persistent imbalances caloric and pendular responses showed unilateral, then contralateral loss with or without recovery of function. Eleven were controlled with a follow-up from 1 to 7 years. Patients of both groups remained permanently or episodically symptomatic, but only 4 patients complained of persistent oscillopsia. Viral infections, systemic diseases (hypertension, hypothyroidism, asthma), immune reactions (vaccination) and toxic factors (herbicide exposure) may play a role in the etiology of this rare bilateral peripheral vestibulopathy.