The differential diagnostic value of a battery of oculomotor evaluation in Parkinson's Disease and Multiple System Atrophy

Introduction: Clinical diagnosis of Parkinsonism is still challenging, and the diagnostic biomarkers of Multiple System Atrophy (MSA) are scarce. This study aimed to investigate the diagnostic value of the combined eye movement tests in patients with Parkinson's disease (PD) and those with MSA.

Methods: We enrolled 96 PD patients, 33 MSA patients (18 with MSA-P and 15 with MSA-C), and 40 healthy controls who had their horizontal ocular movements measured. The multiple-step pattern of memory-guided saccade (MGS), the hypometria/hypermetria of the reflexive saccade, the abnormal saccade in smooth pursuit movement (SPM), gaze-evoked nystagmus, and square-wave jerks in gaze-holding test were qualitatively analyzed. The reflexive saccadic parameters and gain of SPM were also quantitatively analyzed.

Results: The MGS test showed that patients with either diagnosis had a significantly higher incidence of multiple-step pattern compared with controls (68.6%, 65.2%, and versus. 2.5%, p < .05, in PD, MSA, versus. controls, respectively). The reflexive saccade test showed that MSA patients showing a prominent higher incidence of the abnormal saccade (63.6%, both hypometria and hypermetria) than that of PD patients and controls (33.3%, 7.5%, respectively, hypometria) (p < .05). The SPM test showed PD patients had mildly decreased gain among whom 28.1% presenting "saccade intrusions"; and that MSA patients had the significant decreased gain with 51.5% presenting "catch-up saccades"(p < .05). Only MSA patients showed gaze-evoked nystagmus (24.2%), square-wave jerks (6.1%) in gaze-holding test (p < .05).

Conclusions: A panel of eye movements tests may help to differentiate PD from MSA. The combined presence of hypometria and hypermetria in saccadic eye movement, the impaired gain of smooth pursuit movement with "catch-up saccades," gaze-evoked nystagmus, square-wave jerks in gaze-holding test, and multiple-step pattern in MGS may provide clues to the diagnosis of MSA.