Neuropathologic Changes of Multiple System Atrophy and Diffuse Lewy Body Disease

The accumulation of fibrillar a-synuclein protein is the pathological hallmark occurring in both multiple system atrophy (MSA) and diffuse Lewy body disease (DLBD). The oligodendrocytes are especially involved in MSA, while subtypes of neurons are the targets in DLBD. In both instances, the changes are widespread within the central nervous system, but with distinct and topistic vulnerability. Two diagnostic subtypes of MSA are currently applied: multiple system atrophy-cerebellar (MSA-C), formerly designated olivopontocerebellar atrophy, and multiple system atrophy-parkinsonian (MSA-P), formerly called striatonigral degeneration. However, overlaps exist between them, notably during the late stages of the illness. The brainstem and cerebellum are especially vulnerable and dysfunctional in MSA-C, but the striatum and mesencephalon in MSA-P, wherein parkinsonism usually prevails. In DLBD, Lewy-body-containing neurons (LBCN) involve the cerebral cortex in addition to the sites affected in Parkinson disease (PD). Thus, dementia and parkinsonism occur, often without brain atrophy. Then, two main pathological subtypes are used: the limbic or the cortical type. Possibly, DLBD, either the limbic or cortical-type, is the ultimate stage of PD, which corresponds to the brainstem type. The epidemiologic and genetic traits causing sporadic MSA and sporadic DLBD are not known.