OPCA is a group of dominant inheritance and sporadic neurological disorders characterized by a chronic, progressive, cerebellar ataxia that begins in middle age. The cerebellum and its connections are the primary sites of the disease in chronic progressive disorders that often occur in familial or hereditary patterns.
Postmortem studies indicate an atrophy of the cerebellum, pons, and inferior olives.
This neuropathological neuronal cell loss permits classification of OPCA as a non-Alzheimer s neurodegenerative illness. Gross postmortem inspection of the brains of patients with OPCA shows marked shrinkage of the ventral half of the pons, and disappearance of the olivary eminence on the ventral surface of the medulla. These brains also exhibit an atrophy of the cerebellum with degeneration of the middle cerebellar peduncles, and to a lesser extent, of the inferior peduncles. Thus, the cerebellum suffers mainly through atrophy of its afferent fibers. The neocerebellum and the olive undergo the primary degeneration.