Effects of unilateral dysfunction of the inferior vestibular nerve system on postural stability.

OBJECTIVE: To investigate whether disorders of the inferior vestibular nerve (IVN) system affect postural stability.

METHOD: Two-legged stance tasks were performed by patients with unilateral peripheral vestibulopathy (n=108) in four conditions: eyes open or eyes closed, with or without foam rubber. We examined six parameters: the velocity of movement of the center of pressure and the envelopment area determined by tracing the movement in the eyes closed/foam rubber condition, Romberg's ratio of velocity and area with foam rubber, and the foam ratios (ratios of a measured parameter with to without the foam rubber) of velocity and area with eyes closed.

RESULTS: The values of all six parameters were significantly higher in patients with unilateral vestibulopathy whose cervical vestibular evoked myogenic potentials (cVEMPs) were abnormal compared with healthy controls (p<0.01). Four of the six parameters showed significantly higher values (p<0.05) in patients with unilateral abnormal cVEMPs in the presence of normal caloric responses compared with the controls.

CONCLUSIONS: Foam posturography is useful for making a preliminary assessment of unilateral vestibulopathy with abnormal cVEMPs. Selective damage of the unilateral IVN system could affect postural stability.

SIGNIFICANCE: We proved the influence of the disorder of the IVN system on postural stability.