Impulsive testing of semicircular canal function.

After acute vestibular loss in humans or animals, eye-movement responses to rapid horizontal ipsilesional head rotations ("head impulses") show that there is severe, permanent impairment of the angular vestibulo-ocular reflex. The basis for this appears to be an inhibitory saturation of ipsilesional vestibular nerve, and perhaps vestibular nucleus afferents, in response to high-acceleration, off-direction stimulation of the sole functioning member of any pair of semicircular canals. For the clinician, impulsive testing is an easy and reliable way to identify severe unilateral as well as bilateral impairment of semicircular canal function.