The active head-impulse test in unilateral peripheral vestibulopathy.

BACKGROUND The head-impulse test, which is sensitive and specific for detecting severe unilateral peripheral vestibulopathy, is an accepted part of the neurological examination, especially in patients with vertigo and balance disorders. OBJECTIVE To discover if the head-impulse test is just as useful diagnostically when patients are asked to rotate their own heads, the active head-impulse test, rather than when the clinician does so as in the standard passive head-impulse test. METHODS Clinical observation of compensatory saccades and search coil measurement of compensatory eye rotations, during active and passive horizontal head-impulses in 6 patients with total unilateral vestibular deafferentation. RESULTS Clinical observation showed the expected compensatory saccades with rotations toward the side with the lesion with passive head-impulses but not with active head-impulses. Search coil recordings revealed 2 reasons for this. With active head-impulses not only was vestibulo-ocular reflex gain higher, but compensatory saccade latency was shorter resulting in an occult saccade that occurred during, rather than after, head rotation. CONCLUSIONS Passive head-impulses are necessary to detect a severe unilateral peripheral vestibulopathy; active head-impulses will produce a false-negative result.