Dynamic asymmetry of the vestibulo-ocular reflex in unilateral peripheral vestibular and cochleovestibular loss

Objective: Rotatory tests in the horizontal plane have shown various degree s of vestibulo ocular reflex (VOR) asymmetry in patients after surgical dea fferentation of one labyrinth, The purpose of this work was to characterize dynamic horizontal VOR responses among patients presenting with a unilater al peripheral labyrinthine deficit of nonsurgical origin and to compare res ults in isolated vestibular loss versus cochleovestibular loss. Study Desig n: This study included 40 patients who presented with an acute, spontaneous unilateral peripheral labyrinthine lesion. Twenty-two patients had vestibu lar loss alone (without associated hearing impairment) and 18 presented wit h a cochleovestibular deficit (sudden hearing loss with vertigo). The major ity of these patients were part of a long-term protocol to evaluate vestibu lar compensation. Methods: All patients underwent both the clockwise test a nd the counterclockwise rotatory test in the horizontal plane, using brief impulses of moderate intensity. Results mere analyzed by a simplified model of vestibular function, allowing a parametric estimation of the response. Results: A weak and transitory horizontal VOR asymmetry was observed in the 22 patients with vestibular loss. However, the 18 patients with cochleoves tibular loss demonstrated a more severe and persistent asymmetry. Conclusio ns: This study revealed a difference in the dynamic characteristics of the horizontal VOR between patients with vestibular loss and those with cochleo vestibular loss. Our results support the presence of an extensive labyrinth ine lesion in cochleovestibular of this involvement on the central mechanis ms of otolith-canal interaction are discussed.