Smooth Pursuit and Reflexive Saccade in Discriminating Multiple-System Atrophy With Predominant Parkinsonism From Parkinson's Disease

Background and Purpose Performing the differential diagnosis of Parkinson's disease (PD) and multiple-system atrophy of parkinsonian type (MSA-P) is challenging. The oculomotor performances of patients with PD and MSA-P were investigated to explore their potential role as a biomarker for this differentiation. Methods Reflexive saccades and smooth pursuit were examined in 56 patients with PD and 34 with MSA-P in the off-medication state. Results Patients with PD and MSA-P had similar oculomotor abnormalities of prolonged and hypometric reflexive saccades. The incidence rates of decreased reflexive saccadic velocity and saccadic smooth pursuit were significantly higher in MSA-P than in PD (p<0.05 for both). Multiple logistic regression analysis indicated that slowed reflexive saccades (odds ratio [OR]=8.14, 95% confidence interval [CI]=1.45-45.5) and saccadic smooth pursuit (OR=5.27, 95% CI=1.24-22.43) were significantly related to MSA-P. Conclusions The distinctive oculomotor abnormalities of saccadic smooth pursuit and slowed reflexive saccades in MSA-P may serve as useful biomarkers for discriminating MSA-P from PD.