SACCADE VELOCITY IN IDIOPATHIC AND AUTOSOMAL-DOMINANT CEREBELLAR-ATAXIA

Slow saccades are often found in degenerative ataxia. Experimental stu dies have shown that horizontal saccades are generated in the paramedi an pontine reticular formation and that lesions in this area produce s low saccades. Based on these findings, saccade slowing should be a fre quent feature of olivopontocerebellar atrophy, a type of cerebellar de generation with prominent involvement of the pens. To test this hypoth esis, saccade velocity was measured in 31 patients with autosomal domi nant cerebellar ataxia (ADCA) and 17 patients with idiopathic cerebell ar ataxia (IDAC). Saccade velocity was reduced in most patients with A DCA whereas it was normal in IDCA although olivopontocerebellar atroph y occurred in both groups. Saccade velocities correlated with pontine size in ADCA but not in IDCA. The data disprove the hypothesis that sa ccadic slowing is a clinical hallmark of olivopontocerebellar atrophy. Instead, only patients with ADCA and morphological features of olivop ontocerebellar atrophy have slow saccades.