Saccadic deterioration in spinocerebellar degeneration

Abstract

Two frequent findings in cases of inherited ataxias involving the pons are the severe reduction of saccadic velocities and the presence of saccadic hypometria. The patients described here were initially observed to make frequent, severely hypometria refixations, composed of a sequence of small saccades of normal velocity. The saccadic gain was so low that these refixations appeared clinically to be continuous, slow movements. Over time, the small saccades then became slow but the overall movement remained hypometria. Also present initially but becoming more frequent with time were refixations consisting of a single, extremely slow saccade. This longitudinal study revealed a progressive deterioration in the saccadic system, possibly indicating an early defect in the way in which fast eye movements are programmed, followed by dysfunction in the pathways which actually generate them.