This is a complex part of the nervous system, extending from the cortex to the medulla in the BRAIN, from which emerge descending spinal pathways which inﬂuence voluntary motor activity throughout the body. Although the normal functions of the system are poorly understood, there are characteristic signs of an extrapyramidal LESION. These include disturbance of voluntary movements, notably slowness and ‘poverty’ of movement; disturbance of muscular tone, which may be increased or decreased; and involuntary movements, such as a tremor, irregular jerking movements, or slow writhing movements.
Diseases There are several diseases that result from lesions to the extrapyramidal system, of which the most common is PARKINSONISM. Others include WILSON’S DISEASE, KERNICTERUS, CHOREA and ATHETOSIS.