About two thirds of the patients with multiple system atrophy (MSA) do not respond to levodopa treatment. Postmortem pathological studies and one retrospective [¹⁸F]-deoxyglucose positron emission tomography (FDGPET) study attributed such poor response to the striatal degeneration. We prospectively investigated the relationship between levodopa responsiveness and the metabolic activities of the striatum and cerebellum in MSA patients.

In 39 patients with MSA, the UPDRS motor score was assessed and two sets of timed motor tests were perform ed before and after the levodopa treatment. After quantitative FDG PET and baseline evaluation, treatment w as started with 3 tablets of Sinemet^® 25/250 mg a day. Clinical assessments were performed monthly for three months. Metabolic activities of the caudate, anterior putamen, posterior putamen, cerebellar cortex and cerebellar vermis were measured. We compared the measurements with mean percentage changes of motor function. Also, using statistical parametric mapping (SPM) analysis, we tried to find brain areas in which metabolism correlated with the clinical changes.

Mean percentage improvements of UPDRS motor scores w ere correlated with glucose metabolism in the posterior putamen and cerebellar vermis. The mean percentage improvements of performance in Purdue peg board test correlated with the glucose metabolism in the cerebellar cortex and vermis. In SPM analysis, cerebellar glucose metabolism correlated with the improvement of UPDRS motor score and the performance of two timed motor tests.

The integrity of cerebellum, as well as posterior putamen, may be an important factor for showing the response to levodopa.