Case with both multiple system atrophy and primary progressive multiple sclerosis with discussion of the difficulty in their differential diagnosis.

Multiple system atrophy (MSA) manifests as a relentlessly progressive disor der incorporating varying combinations of autonomic, cerebellar, and pyrami dal dysfunction, and parkinsonism. Primary progressive multiple sclerosis ( MS) may also manifest as a progressive disorder incorporating bladder distu rbance, and cerebellar and pyramidal dysfunction. Parkinsonism has also bee n rarely reported in multiple sclerosis, but whether as a consequence of de myelination or as a result of some other coexistent basal ganglia disease r emains controversial. We here report an unusual instance of the coincidence in one patient. both clinically and neuropathologically, of MSA and primar y progressive MS, and consider the difficulty of differentiating between th em.