Disturbed vestibular-neck interaction in cerebellar disease.

Cerebellar dysfunction results in ataxia including postural deficits. Evidence from animal experiments suggests convergence of vestibular and neck-position related inputs in cerebellar midline structures. We investigated 20 ambulatory patients with cerebellar disease for disturbed postural control using posturography during static lateral head turns. Binaural bipolar sine-wave galvanic vestibular stimulation (GVS) was used to evoke specific body movements. The Klockgether clinical score was used to assess the severity of cerebellar dysfunction (4-17 of maximal 35 points). In 12 healthy controls and seven lightly affected patients (score <8), GVS elicited physiologic alternating body sway in the head-frontal plane in seven head-on-trunk positions (0°; 30°, 45° and 60° left and right). Body sway turning with head excursion was progressively attenuated or abolished in more severely affected patients (scores 9-17; r = 0.57, p = 0.008). With most severe impairment, body sway was always in the body-frontal plane irrespective of head turn. A simple clinical test with walking under maximal head turn and closed eyes correlated with posturography data (r = 0.87, p < 0.001) and with Klockgether scores (r = 0.71, p < 0.001). Thus in cerebellar disease, head on trunk position can have a pronounced effect on postural control.