Vestibular compensation after hemilabyrinthectomy: effects of trigeminal neurotomy.

The unilateral section of the trigeminal trunk was performed in 25 guinea pigs after compensation from right hemilabyrinthectomy. To avoid lesion of the cerebral cortex the trigeminal nerve was approached ventrally through the foramina lacerum and ovale which are fused in the guinea pig. Complete section of a trigeminal nerve induced reappearance of already compensated hemilabyrinthectomy symptoms: head and trunk torsion to the right, extension of left forelimb, eye nystagmus to the left, circling and rolling movements to the right, and impairment of body and head righting reflexes from lateral decubitus. These symptoms persisted for 6–8 hr after trigeminal neurotomy. Thus sensory trigeminal afferents seem to contribute to the mechanism of vestibular compensation.