HORIZONTAL OTOLITH-OCULAR RESPONSES TO LATERAL TRANSLATION IN BENIGN PAROXYSMAL POSITIONAL VERTIGO

Benign paroxysmal positional vertigo (BPPV) is assumed to result from utricular damage, but it is controversial if patients have manifest ut ricular dysfunction. Therefore, we investigated linear vestibule-ocula r reflexes (LVORs) during lateral whole-body translation in 14 patient s with unilateral BPPV. Patients were subjected to linear acceleration steps of 0.24 g along the interaural axis, which were applied randoml y to the left and right, both in the dark and in the light with a visu al target at a distance of 60 cm. The LVOR was measured by EOG from th e slow phase velocity of the averaged and desaccaded compensatory eye movement. In normal cases, maximum asymmetry of LVOR velocity was 13% in the dark and 10% in the light. In patients, LVOR velocities were no rmal in the dark but mildly reduced in the light (p < 0.05). Five pati ents had mild LVOR asymmetries in the dark (range 18-38%) and two in t he light (11 and 13%). but there was no consistent relationship to the affected side. The absence of gross changes of the LVOR may be explai ned either by minor utricular damage that is functionally irrelevant o r by central compensation of a chronic unilateral deficit.