Reversed Corrective Saccades during Head Impulse Test in Acute Cerebellar Dysfunction

Abstract

Patients with cerebellar lesions may show horizontal (positive)- or downward (perverted)-corrective saccades during horizontal head impulse test (HIT). However, corrective saccades in the direction of head rotation (reversed corrective saccades) have not been reported during HIT. We present two patients who showed reversed corrective saccades during horizontal HIT as an initial sign of acute cerebellitis. In contrast to the corrective saccades mostly observed in peripheral vestibular paresis, this paradoxical response indicates abnormally increased vestibulo-ocular responses due to cerebellar disinhibition over the vestibulo-ocular reflex. This paradoxical response should be considered an additional bedside cerebellar sign.