Routine MRI for the differential diagnosis of Parkinson's disease, MSA, PSP, and CBD.

We assessed the usefulness of routine MRI for the differential diagnosis of Parkinson's disease (PD) with "atypical" parkinsonian syndromes in everyday clinical practice. We studied routinely performed MRI in PD (n = 32), multiple system atrophy (MSA, n = 28), progressive supranuclear palsy (PSP, n = 30), and corticobasal degeneration (CBD, n = 26). From a preliminary analysis of 26 items, 4 independent investigators rated 11 easily recognizable MRI pointers organized as a simple scoring system. The frequency, severity and inter-rater agreement were determined. The total severity score was subdivided into "cortical", "putaminal", "midbrain", and "pontocerebellar" scores. The frequency of putaminal involvement (100%) and vermian cerebellar atrophy (45%) was significantly higher in MSA, but that of cortical atrophy (50%), midbrain atrophy and 3(rd) ventricle enlargement (75%) was higher in PSP and CBD. The median total score fairly differentiated "atypical" parkinsonian syndromes from PD (positive predictive value-PPV-90%). However, the median total score was unable to differentiate atypical parkinsonian syndromes each other. The "cortical" score distinguished CBD and PSP from MSA with a fair PPV (>90%). The PPV of the "putaminal" score was high (70%) for the differential diagnosis of MSA with PSP and CBD. The "midbrain" score was significantly higher in PSP and CBD compared to MSA. These results are in accordance with the underlying pathology found in these disorders and demonstrate that a simple MRI scoring procedure may help the neurologist to differentiate primary causes of parkinsonism in everyday practice.