Definition: A sporadic neurodegenerative disease with onset in middle-age characterized clinically by Parkinsonian features (e.g., MUSCLE RIGIDITY; HYPOKINESIA; stooped posture) and HYPOTENSION. This condition is considered a clinical variant of MULTIPLE SYSTEM ATROPHY. Pathologic features include a prominent loss of neurons in the zona compacta of the SUBSTANTIA NIGRA and PUTAMEN. (From Adams et al., Principles of Neurology, 6th ed, p1075-6)
