Is multiple system atrophy with cerebellar ataxia (MSA-C) like spinocerebellar ataxia and multiple system atrophy with parkinsonism (MSA-P) like Parkinson's disease? - A saccade study on pathophysiology.

OBJECTIVE: Patients with multiple system atrophy (MSA) are classified into those mainly manifesting cerebellar ataxia (MSA-C) and those mainly manifesting parkinsonism (MSA-P). Pathophysiological bases of these subtypes remain unclear. We hypothesized that MSA-C patients would resemble spinocerebellar degeneration patients and MSA-P patients would resemble Parkinson's disease (PD) patients in saccade abnormalities.

METHODS: We recorded visually guided and memory guided saccades (MGS) in 27 MSA-C and 15 MSA-P patients, as well as 50 age-matched normal subjects, 14 spinocerebellar degeneration patients showing pure cerebellar symptoms (SCD) and 61 Parkinson's disease (PD) patients.

RESULTS: Saccade parameters of both tasks showed similar changes with progressing disease in SCD and MSA-C patients, as did those of MSA-C and MSA-P patients, although hypometria was slightly more pronounced in MSA-P. In both subtypes of MSA, latency and success rate of MGS were stable throughout disease stages, whereas they deteriorated progressively with progressing disease in PD.

CONCLUSIONS: Pathophysiology underlying MSA-C and MSA-P is similar as viewed from saccade performance. The MGS performance in MSA was preserved. However, MSA-P patients showed more marked hypometria, suggesting a mixture of basal ganglia pathophysiology.

SIGNIFICANCE: The similarity of saccade performance between MSA-C and MSA-P may reflect common olivopontocerebellar pathology, while the direct pathway of the basal ganglia is relatively spared compared with PD, even in MSA-P.