Intralabyrinthine schwannoma affecting the low but not high frequency function of the vestibulo-ocular reflex: Implications for the clinical diagnosis of chronic peripheral vestibular deficits

Peripheral vestibular hypofunction can be identified by asymmetric vestibular responses to caloric irrigation of the horizontal semicircular canal or by the head impulse test.1 Whereas the first test investigates the low frequency function of the vestibulo-ocular reflex (VOR) the latter assesses the high frequency function. The high frequency VOR function is usually more persistently impaired in unilateral vestibular lesions (eg, vestibular neuritis) than the low frequency function and thus the more sensitive parameter to detect chronic peripheral vestibular deficits.2

Contrary to this current vestibular knowledge, we present a patient with a chronic peripheral vestibular deficit showing normal high frequency but impaired low frequency VOR function. This unusual lesion pattern was caused by an intralabyrinthine schwannoma.