Body sway response to experimental unbalance in normal subjects and patients with unilateral vestibular disorders.

The function of maintaining posture during temporary unbalance caused by experimental vestibular asymmetry was studied. Galvanic stimulation to the vestibular nerve causing body deviation to the stimulated ear was given to 31 normal subjects and 16 patients with peripheral vestibular disorders. The velocity of spontaneous body sway and that during body deviation caused by the galvanic stimulation were compared. The spontaneous body sway velocity was significantly higher than that of normal subjects. In normal subjects, the body sway velocity during body deviation remarkably increased, while that in patients did not. It is considered that large body sway in patients might conceal the fine compensatory body sway during the body deviation and that patients with unilateral vestibular dysfunction who have large body sway are always in a dysfunction state similar to that which normal subjects experience during body deviation caused by galvanic stimulation.