[Optokinetic nystagmus associated with Parkinson's disease]

Optokinetic nystagmus is a complex many-level physiological reaction underlain by the mechanisms of oculomotor reaction and dependent on the correlated regulatory action of the upper parts of CNS. The objective of the present study was to estimate the quantitative parameters of optokinteic nystagmus in the patients presenting with clinically manifest Parkinson's disease (PD) with due regard for the character of optokinetic stimulation. It was shown that PD is associated with a decrease of velocity-related parameters of optokinetic nystagmus correlated with the severity of the disease. The decrease of velocity in the slow phase and the efficacy coefficient of vertical optokinetic nystagmus was more pronounced in comparison with horizontal nystagmus. It was totally absent in certain patients with stage IV of the disease which objectively reflects the overall motor deficiency associated with PD and manifest as the predominant involvement of mechanisms of the vertical oculomotor system.