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Parkinsonism--Physiology and Pharmacology

1971; BMJ; Volume: 3; Issue: 5776 Linguagem: Inglês

10.1136/bmj.3.5776.693

0959-8138

D. B. Calne,

Parkinson's Disease Mechanisms and Treatments

and basal ganglia, but the detailed anatomical connexions and physiological role of these areas of the central nervous system are so complex that at present their function in motor control remains uncertain. The term extrapyramidal was coined 70 years ago130 to embrace all motor pathways other than the direct projection from the motor cortex to the spinal cord via the medullary pyramid (the pyramidal or corticospinal pathway). Functional disturbance of the extrapyramidal system, in particular the basal ganglia, was thought to result in a group of clinical disorders characterized by invol untary movements. Probably many features of this simple scheme will prove to be incorrect as neurophysiology develops. Already the concept of an extrapyramidal system is beginning to appear redundant, as one of the important output pathways from the basal ganglia is the pyramidal tract131?and even such simple entities as involuntary movements are proving difficult to define in physiological terms because, for example, Parkinsonian tremor can often be temporarily abolished by conscious effort, while voluntary movement, such as walking, can be executed without conscious effort. If these examples seem contrived, how should such movements as those involved in breathing be classified ? While acknowledging these difficulties, it is still desirable to consider the physiology of the basal ganglia, and its disturbance in Parkinsonism.