Directional Asymmetries of Saccadic Hypometria in Patients with Early Parkinson’s Disease and Unilateral Symptoms

Abstract

Background: Saccade may be abnormal in Parkinson’s disease (PD), but there have been no systematic studies on directional asymmetries of horizontal saccades in early PD. The aims of this study were to determine the saccadic abnormalities and their directional asymmetries. Methods: We recorded visually guided horizontal prosaccades with random (random amplitudes and irregular time intervals) and regular (fixed amplitude and regular time interval) paradigms using video-oculography in 44 patients with unilateral symptoms and signs from early PD and in 26 controls. Results: PD patients showed decreased saccadic amplitude compared to the controls, especially during regular paradigm while the saccadic latency did not differ between the groups. Patients with unilateral PD tended to show more severe saccadic hypometria toward the symptomatic side during the regu- lar paradigm, compared to normal control. Conclusion: Even in early PD patients, saccadic accuracy may be abnormal. Asymmetries in saccadic hypometria are more likely to be detected during the anticipatable saccadic paradigm, which could be a useful adjunct in the diagnosis of early-stage PD.