Backgrounds: This study aims to characterize eye movement abnormalities in Wilson disease and examine their association with the degree of brainstem atrophy.
Methods: Twenty patients (10 males, mean age 46.8, SD 8.9 years) with genetically confirmed neurological WD on stable anti-copper treatment and 20 age- and sex-matched healthy subjects were examined. Eye movements, including prosaccade and antisaccade tasks, were evaluated using infrared videooculography. MRI was performed using 1.5 T system, and T2-weighted images 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).
Results: Compared to healthy controls, WD patients showed prolonged latencies of horizontal prosaccades and hypometry of both horizontal (p = 0.04) and vertical (p = 0.0046) prosaccades. In the antisaccade task, WD patients showed prolonged latency of both horizontal (p = 0.04) and vertical antisaccades (p = 0.047) and increased error rate of vertical antisaccades (p = 0.04). There is a significant association between midbrain area and horizontal latencies (r = -0.53; p = 0.02) and vertical maximum speed in prosaccades (r = 0.47; p = 0.04). The pons area inversely correlated with horizontal prosaccade and antisaccade latencies (p = 0.007).
Conclusions: We showed impairments of ocular saccades such as prolonged latencies, hypometry, and increased error rate in antisaccades. The strong association between prolonged latencies of prosaccades and the brainstem atrophy suggests that VOG might serve as a sensitive electrophysiological marker of brainstem dysfunction in WD.
Keywords: Brainstem; Eye movement; Wilson disease.