Grading of neuropathology in multiple system atrophy: proposal for a novel scale

Multiple system atrophy (MSA), a sporadic progressive synucleinopathy of advanced age, is separated into two clinic opathological subtypes: MSA-P (striatonigral degeneration [SND]) with predominant parkinsonian features and MSA-C (olivopontocerebellar atrophy [OPCA]) with predominant cerebellar ataxia. We propose a novel morphological grading system for both subtypes to compare lesion intensities and their possible clinical validity. Forty-two autopsy cases of MSA were separated into four grades (SND 0-III and OPCA 0-III) based on semiquantitative assessment of neuronal loss, astrogliosis, and presence of alpha-synuclein-positive glial cytoplasmic inclusions (GCI) in striatum, globus pallidus, substantia nigra, pontine basis, cerebellum, and inferior olives. Whereas a recent grading system restricted to SND reflected disease progression and dopa-responsiveness, there was considerable variation in the morphological combination between SND and OPCA, with only around half the cases with OPCA II (moderate) and III (severe) showing comparable grades of both types, whereas OPCA 0 and I (no or little degeneration) was combined with all grades of SND. Twenty-two cases showing OPCA 0 + SND II (n = 3), OPCA I + SND I-II (n = 11), and OPCA I + SND III (n = 8) were classified as pure or predominant SND, consistent with MSA-P. Twenty cases showing OPCA II + SND II/III (n = 7) and OPCA III + SND III (n = 13) were classified as predominant OPCA, consistent with MSA-C. In MSA-P, the mean age of onset was higher than it was in MSA-C (55.1 vs. 50.5 years), but the mean duration of illness was shorter in MSA-P (5.3 vs. 6.7 years). Presenting symptoms in MSA-P were mainly parkinsonism, whereas in MSA-C they were mainly gait disorders (14 vs. 1; P < 0.001). Among clinical key symptoms, parkinsonism was more frequent than were cerebellar signs in MSA-P; in MSA-C it was the reverse (P < 0.01), whereas other symptoms (autonomic/urinary failure) showed no differences. Parkinsonism was infrequent in MSA-C even when OPCA was associated with SND, suggesting a masking effect by cerebellar system involvement. High terminal Hoehn and Yahr stages were more frequent in MSA-P (P < 0.01), some with good-to-moderate initial levodopa (L-dopa) response. Although the proposed morphological grading of both MSA-P and -C correlates well with initial symptoms and clinical key features of both types, further prospective studies are required to validate the clinical utility of the proposed MSA grading scales for future intervention studies.