Objective: To analyse oculomotor differences among idiopathic PD patients (iPD), LRRK2-G2019S PD patients (LRRK2-G2019S PD), asymptomatic carriers of LRRK2-G2019S mutation (AsG2019S), and controls, evaluated by video-oculography.

Background: Some oculomotor deficits, such as hypometric saccades or antisaccade errors, have been described in the physical examination of PD patients. Video-oculography constitutes a quantitative, highly-sensitive method of characterizing ocular movements. We hypothesize that some oculomotor changes arise in the premotor stage and, therefore, could be useful as early disease biomarkers.

Method: Participants underwent a video-oculographic evaluation that included a fixation test, a prosaccade test, an antisaccade test, and a memory saccade test. We used general linear models to analyse oculomotor differences among groups and linear regression to explore associations between oculomotor parameters and UPDRSIII scores. All results were age and sex adjusted.

Results: The study included 116 subjects: 16 iPD (mean age 66.3 years, 11.1 SD); 14 LRRK2-G2019S PD (69.3 years, 13.6 SD); 23 AsG2019S (61.5 years, 8.4 SD); and 63 controls (63.3 years, 5.9 SD). We did not find significant differences between iPD and LRRK2-G2019S PD. Compared to controls, PD patients displayed widespread oculomotor deficits including hypometric vertical prosaccades (negative error: -1.04° vs -0.29° in controls, p 0.0025), increased latencies in all tests, and lower percentages of correct responses in the antisaccade (p<0.001) and memory saccade tests (p 0.010). In the fixation test, both PD patients and AsG2019S showed larger microsaccades than controls. AsG2019S individuals reached similar percentages of success in the antisaccades and memory saccade tests as controls; however, they showed increased latencies in all tests (prosaccades: 291.5 ms vs 263.0 ms in controls, p 0.0030) and also hypometric vertical prosaccades (negative error -0.57°, p 0.0036). UDRSIII scores were positively correlated with prosaccade and antisaccade latencies and negatively correlated with the percentage of correct responses in the antisaccade test (r -0.52, p<0.001).

Conclusion: iPD and LRRK2-G2019S PD patients do not seem to display a differential oculomotor profile. AsG2019S individuals show several oculomotor changes that could be considered premotor biomarkers.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/oculomotor-changes-in-the-premotor-stage-of-lrrk2-g2019s-associated-parkinsons-disease/