Impaired oculomotor function in a community-based patient population with newly diagnosed idiopathic parkinsonism

The differential diagnosis of idiopathic parkinsonism can be very challenging, especially early in the course of the disease. Oculomotor function has been reported to differ between the diseases constituting idiopathic parkinsonism. A detailed examination of the oculomotor functions could thus possibly be useful in the early differential diagnostic procedure. Oculomotor function could also differ between subgroups of patients with Parkinson's disease (PD). We examined the oculomotor function in a population-based incidence cohort with newly diagnosed idiopathic parkinsonism and 38 controls. We examined 135 patients with parkinsonism 105 PD, 11 progressive supranuclear palsy (PSP), and 19 multiple system atrophy with predominant parkinsonism (MSA-P)] within 3 months of their first visit to our clinic and before initiation of dopaminergic medication. The oculomotor measurements were repeated after 12 months. The clinical diagnosis was that of the latest clinical follow-up (median follow-up was 3 years). All patients were examined with (123)I-N-(omega)-fluoropropyl-2-β-carbomethoxy-3-β-(4-iodophenyl) nortropane single-photon emission computed tomography (FP-CIT SPECT), and only patients with pathological uptake of the ligand were included. Pathological changes in the oculomotor function were found in all patient groups compared to controls at the baseline examination. In PD, there were correlations between total axial motor scores and vertical saccade velocity and precision, horizontal saccade velocity and precision, and smooth pursuit gain at 20 and 30°/s. Oculomotor test results could not separate the different forms of idiopathic parkinsonism in the early phase from each other. Few changes in the oculomotor functions were observed between the baseline and the 12-month follow-up examinations. No correlations were found between the oculomotor measurements and disease severity or duration.