Fluctuations in tremor at rest and saccadic eye movements in subjects with Parkinsons disease.

Overview

This study investigates the possible relationships between fluctuations in finger tremor amplitude and the performance of visual saccades. Saccadic eye movements were analyzed in five subjects with Parkinson's disease (PD) and five age-matched controls. Tremor was recorded by using a position laser system, and eye movements were recorded with an infrared reflectometry technique (Ober2). Tremor amplitude (root mean square) was significantly larger in the group of subjects with PD (2.87 +/- 4.37 mm) than in the control group (0.017 +/- 0.005 mm, U = 0, p < 0.01). In addition, subjects with PD showed more fluctuations in their tremor at rest (0.52 +/- 0.98 mm versus 0.003 +/- 0.006 mm, U = 1, p < 0.05). Latency, saccade error and percentage of predictive saccades were not significantly different between subjects with PD and control subjects. Average saccade amplitude was smaller in the group of subjects with PD (16.1 +/- 2.31 degrees ) than in the control group (18.49 +/- 3.62 degrees , U = 1, p < 0.05). Spearman's rank correlation coefficient showed no direct relationship between saccade amplitude and changes in tremor amplitude at the time of each saccade but, in general, subjects with PD who had more fluctuations in their tremor at rest had also more fluctuations in their saccade error (Rho = 0.9). These results suggest that the mechanisms causing short-term fluctuations in tremor at rest do not directly influence the visual saccadic system.