BILATERAL IDIOPATHIC LOSS OF PERIPHERAL VESTIBULAR FUNCTION WITH NORMAL-HEARING

From 1982 to 1993, 52 electronystagmograms (ENG) revealed an absent ny stagmic reaction on both caloric (44-30 and 10 degrees C water irrigat ion) and rotatory pendular testing (0.05 Hz/peak velocity 60 degrees/s ), which represents 0.6% of all ENG performed during this period. Amon g these examinations, 14 patients (27%) presented a bilateral idiopath ic loss of vestibular function (BILVF) with normal hearing and without associated neurological symptoms. Two different groups emerged: one g roup with simultaneous onset of BILVF (10 patients), with sudden imbal ance and disequilibrium, worse in darkness, with an absence of bilater al caloric and pendular response. The other group (4 patients) was cha racterized by sequential onset of BILVF. These patients experienced se veral episodes of acute vertigo with persistent imbalance; 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 ep isodically symptomatic, but only 4 patients complained of persistent o scillopsia. Viral infections, systemic diseases (hypertension, hypothy roidism, asthma), immune reactions (vaccination) and toxic factors (he rbicide exposure) may play a role in the etiology of this rare bilater al peripheral vestibulopathy.