Efferent Connections of the Human Striatum and Pallidum: A Nauta Degeneration Study

Knowledge of the organization and connections of the basal ganglia has greatly advanced in recent years, and, concurrently, understanding and neurosurgical treatment of movement disorders of basal ganglia origin, primarily Parkinson’s disease, have significantly improved. Models of basal ganglia-thalamo-cortical circuitry have been developed to account for both normal function and motor disorders (DeLong, 1990), but these rely primarily on hodological data extrapolated from experimental animals. Direct investigations of basal ganglia output connections in the human brain are rare and often impeded by lesions encroaching upon the capsule, thus rendering interpretations of the origin of degeneration difficult (Martinez, 1961; Beck and Mignami, 1968; Rye et al., 1995). Moreover, these studies were conducted in the brains of parkinsonian patients already presenting pathological features due to the disease. The present study on the distribution of axonal degeneration resulting from lesions confined to the striatum and pallidum provides additional significant information on the pallidofugal pathways in man, especially on those from the external segment, which may have particular relevance in the physiopathology of movement disorders.