Comparison of cerebral atrophy evaluated by MRI in Parkinson's disease and multiple system atrophy

Cerebral atrophy was evaluated in 31 patients with Parkinson's disease (PD) and 24 patients with clinically probable multiple system atrophy (MSA). Measurements of ventricular and brainstem areas, obtained from axial and sagittal MRI sections, were performed using a computer digitalizing system. Cortical and cerebellar atrophies were subjectively assessed. All measures were stored by one observer who was blind to the diagnosis (BD). Age, sex, levodopa dosage, baseline motor Parkinsonian disability (i.e. without levodopa treatment) and neuropsychological impairment were not significantly different between the two groups of patients. The total brainstem area (p < 0.001), the mesencephalon (p < 0.05) and the pens (p = 0.05) areas were significantly smaller in MSA as were the lobar (p < 0.05) and the vermian (p < 0.01) parts of the cerebellum. In the MSA group, significant correlations were observed between the brainstem area and items from the motor part of the Unified Parkinson's Disease Rating Scale (dysarthria, posture, arising from a chair), and between the cerebellar atrophy and the gait disturbance. A progressive discriminant analysis using radiologic variables correctly classified 79% of patients in their own diagnosis group with a significant difference (p = 0.01). From these results, it appears that MRI could help to differentiate MSA from PD, especially when MRI detects a severe infratentorial atrophy suggestive of MSA. However, brainstem and cerebellum atrophies are not sufficient criteria to differentiate MSA from PD because they lack both specificity and sensitivity.