Objective: To explore possible different patterns of acute saccadic responses to Levodopa Challenge Test (LCT) in a de novo drug-naïve Parkinson’s Disease (PD) population and possible differences in clinical progression.

Background: Saccadic eye movements abnormalities were described in PD. Few studies with small sample sizes assessed Levodopa (LD) effects on a drug-naïve population through a standardized LCT, providing conflicting evidences. We hypothesized that these inconsistent findings were related at least in part to an intrinsically heterogeneous saccadic LD response in PD. Here we aimed to test this hypothesis in a drug-naïve PD population, exploring possible prognostic implications.

Method: Patients fulfilling MDS criteria for PD were enrolled. Eye movements were recorded by Eyelink 1000 Plus. Visually-guided saccades were assessed at baseline and after 2 hours from the administration of Levodopa/Carbidopa 250/25 mg. Saccadic velocities, latencies and accuracy were assessed. Nonhierarchical cluster analysis using k-means method was performed based on peak-of-dose parameters. Main sequence and saccadic latencies distribution analysis were performed. Patients were clinically followed-up at 2 years.

Results: Thirty-two de novo PD patients were enrolled. Two clusters were identified among PD patients: Cluster A (21 patients) and B (11 patients). No significant differences in demographical characteristics and clinical assessment both at baseline and peak-of-dose were found between clusters. Improved saccadic velocities and accuracy as well as increased latencies were found at peak-of-dose in cluster A. An opposite trend was demonstrated in cluster B. Different main sequence patterns were found between clusters. An increased cumulative frequency of short-latency saccades was found at peak-of-dose in Cluster B. After a 2 years follow-up, Cluster B patients referred more autonomic symptoms and LD side effects as respect to Cluster A patients.

Conclusion: Different patterns of saccadic LD responses were demonstrated among de novo PD. We identified a cluster of patients with worse oculomotor response to LD who prospectively developed more autonomic symptoms and intolerance to dopaminergic treatment, as expression of poorer outcome. Further studies are needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/different-patterns-of-acute-saccadic-responses-to-levodopa-challenge-test-in-de-novo-parkinsons-disease-possibile-prognostic-implications/