Bilateral Vestibular Loss, Oscillopsia, and the Cervico‐Ocular Reflex

Abstract

Oscillopsia during head movement occurs in patients with bilateral vestibular loss and may be transient or persistent. To investigate mechanisms underlying recovery we tested the vestibulo-ocular reflex (VOR), visual-vestibular interaction, and the cervico-ocular reflex (COR); we used a pseudorandom oscillatory stimulus with a frequency band width of 0 to 5 Hz in six patients with bilaterally absent caloric responses and in 10 normal controls. Seven control subjects had low-gain COR responses, but these were anticompensatory with respect to the VOR. Three asymptomatic patients with an absent or grossly deficient VOR had increased oculomotor responses at all frequencies when oscillated in light. Compensatory COR responses were detected in these patients but not in patients with persisting oscillopsia. In some patients with bilateral vestibular loss, augmented cervico-ocular and visual reflexes may compensate, at least partially, for an absent VOR.

Recovery of Gaze Disturbance in Bilateral Labyrinthine Loss

“…These find ings suggest that the VOR, equipped with numerous subsystems to meet various re quirements, is a system oriented to gaze sta bilization in the light. Recovery of oscillopsia in patients with bilateral labyrinthine loss may be related to restriction of head move ments [2,4,5], perceptual adaptation [3] and initiation and increase of compensatory eye movement [2][3][4][5]9].…”

“…Even under passive rotation, VOR gain in creased linearly against a logarithmic time scale, although recovery was slower and more limited. Thus, the cervico-ocular reflex [2][3][4][5]9] and/or central preprogramming [2][3][4][5] may play major roles in the recovery of VOR gain. Inputs like proprioception or sounds [2,3,5] as well as central prepro gramming [2][3][4][5] or amplification of the ves tigial inputs [7,8] should be candidates un der passive rotation.…”

“…In man, gaze disturbance in unilateral lesions recovers within 1 year in accordance with a decreased imbalance of vestibulo-ocular reflex (VOR) accomplished mainly by an increase in VOR gain upon rotation to the affected side [7], Although gaze disturbance in bilateral lesions is hard to be compensated, the degree of oscillopsia markedly varies among different subjects [8,9,11] and perceptually becomes less with time [12], Many different strategies have been proposed: cervico-ocular reflex [2][3][4][5]9], central preprogramming [2][3][4][5], substitution by vision [3,9], perceptual ad aptation at the higher cortex [3], plastic change of the VOR [7,8], recalibration of the saccade, and restriction of head move ments [2,4,5],…”

Der beidseitige Vestibularisausfall

“…Kompensationsmechanismen bei fehlender Blickstabilisierung unter schnellen Kopfbewegungen nach Wegfall des VOR angenommen [4,5,9,13].…”

“…sowie zentrale Mechanismen der Unterdrückung bewegter Netzhautabbildungen ("retinal slip") bei denen dann nur während ruhiger, bewegungsarmer Phasen visuelle Informationen an das Gehirn weitergeleitet werden [4,5,9,13]. Möglicherweise sind aber auch erlernte Vermeidungsstrategien mit der Durchführung langsamerer Kopfbewegungen, bei denen die oben genannten Kompensationsmechanismen physiologischerweise besser greifen, von Bedeutung [3,4].…”