sciEye movement abnormalities in essential tremor versus tremor dominant Parkinson’s disease

Publication date: Available online 23 February 2019

Source: Clinical Neurophysiology

Author(s): F. Visser, L.J. Bour, Y.X. Lee, T.R. ten Brinke, A.F. van Rootselaar

Abstract

Objective

To show that eye movement abnormalities differ between essential tremor (ET) and tremor dominant Parkinson's disease (PD-T), and that these abnormalities reflect cerebellar dysfunction in ET and basal ganglia pathology in PD-T.

Methods

In this exploratory study, in 23 patients with ET, 21 age-matched patients with PD-T, and 19 age-matched healthy controls (HCs), we investigated visually guided saccades, antisaccades, and smooth pursuit eye movements (SPEM).

Results

While the ET group had a normal gain (saccade amplitude/target amplitude) and latency of saccades, the PD-T group had hypometric visually guided saccades, and a prolonged latency of visually guided saccades and antisaccades. The SPEM gain was similarly low in both ET and PD-T and was significantly lower in both patient groups than in the HC group.

Conclusions

In ET, SPEM gain was reduced in the presence of normal saccades, whereas in PD-T, the reduced SPEM gain was accompanied by delayed saccade initiation and hypometric saccades, in line with cerebellar dysfunction in ET and basal ganglia dysfunction in PD-T.

Significance

These findings support the presumed cerebellar pathology in ET. In addition, the difference in saccade features may contribute to the groundwork for a quantitative diagnostic test to differentiate between these disorders.

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