Head-eye coordination in normals and in patients with vestibular disorders

Oculomotor response in the absence of vision was examined in 8 normal subjects, 11 unilaterally labyrinthectomised patients and 2 patients with suspected bilateral canal paresis. The experiments involved (a) voluntary oscillation of the head, (b) whole body oscillation on a turntable and (c) stimulation of neck afferents by oscillation of the body with the head fixed. In the patients with unilateral lesions there was a directional preponderance of the slow phase eye velocity towards the side of the lesion which differed significantly from that of the normal population. In the patients with bilateral paresis the oculomotor response to whole body oscillation was negligible, whereas the response to voluntary head movement had a mean gain of 0.45 and at high frequency could not be suppressed when viewing a head-fixed image. The saccadic activity during voluntary head movement was similar in all subjects and was correlated with slow phase velocity.