Objective: This study aims to characterize eye movement (EM) abnormalities in Wilson´s disease (WD) and to assess their relation to clinical severity of WD and to the degree of brainstem atrophy.

Background: WD is an inherited disorder of copper metabolism affecting mainly liver and brain. Cerebral copper accumulation affects the basal ganglia, brainstem, cerebellum, and cerebral cortex. A marked basal ganglia and brainstem atrophy is frequently observed in WD. Movement disorders are the most frequent manifestations in WD. Also, abnormalities of saccadic EM are often found in patients with WD, however EM metrics in WD have not been well described so far.

Methods: Twenty patients (10 males, mean age 46.8, SD 8.9 years) with genetically confirmed neurological WD on stable metalochelate treatment and 20 age and sex matched healthy subjects were examined. EM were evaluated using infrared videooculography (VOG). VOG recordings depicted visually guided reflexive saccades elicited in horizontal and vertical plane (the prosaccade task) and voluntary EM in the direction opposite to the side where a stimulus is presented (the antisaccade task). MRI was performed using 1.5T system and T2-weighted images (resolution 0.5×0.5×1 mm3, TE=233ms, TR=2250ms) were used for the measurement of midbrain and pontine area on mid-sagittal slices. Clinical severity was assessed using the Unified Wilson’s Disease Rating Scale (UWDRS). The WD patients were divided in two subgroups, mild (UWDRS≤10) and severe (UWDRS>10).

Results: Compared to healthy controls, WD patients showed prolonged latencies of horizontal prosaccades and decreased gain (= hypometry) of both horizontal and vertical prosaccades [fig.1]. In the antisaccade task, WD patients showed prolonged latency of both horizontal and vertical antisaccades and increased error rate of vertical antisaccades [fig.2]. More severely affected WD patients presented a higher error rate in the antisaccade task compared to mild WD patients. The pons area inversely correlated with horizontal prosaccade (r = -0.599; p = 0.001) and antisaccade latencies (r = -0.713; p = 0.007). No correlations were found between the midbrain area and any VOG parameter.

Conclusions: Prolonged latencies and hypometry of ocular pro- and antisaccades together with the correlation found between the latency of horizontal pro- and antisaccades and the pons area suggest a specific involvement of the brainstem oculomotor structures in WD. On the other hand, the relationship found between clinical severity of WD and error rate in the antisaccade task may be a rather non-specific reflection of other brain structures involvement.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/eye-movement-abnormalities-correspond-to-pontine-atrophy-in-wilson-disease/