Stereotaxis in the treatment of parkinsonism.

UNTIL a few years ago the only worth-while operation for Parkinsonism was complete division of the lateral column of the spinal cord at the level of the second cervical segment (Oliver, I950), but arrest of tremor was obtained at the cost of weakness of the arm and leg and some sensory loss on the opposite side and, furthermore, this operation was applicable to unilateral Parkinsonism only (Oliver, I953). The results of this operation were confirmed by other workers (Sj6qvist, I954; Gaches, 1955). Walker (I949) had tried the effect of dividing the pyramidal fibres in the cerebral peduncle; sensory loss was avoided, but there was considerably greater weakness of the arm and leg than after the cervical operation. A revolutionary advance in the surgical treatment of Parkinsonism was fortuitously initiated when Cooper (I953, 1954), while exposing the cerebral peduncle to carry out Walker's pedunculotomy, accidentally damaged the anterior choroidal artery and was obliged 'to coagulate it. (The anterior choroidal artery arises from the internal carotid just above the posterior communicating artery and is adjacent to the cerebral peduncle). The operation was then abandoned, but the patient was nevertheless found to be free from tremor on the opposite side, and none of the anticipated neurological disturbances were produced on this occasion. According to experimental work on the anterior choroidal artery (Abbie, 1933), at least a hemiplegia and homonymous hemianopia were anticipated. As a result of this unexpected experience Cooper continued for a time deliberately to coagulate the anterior choroidal artery for Parkinson's disease. The beneficial effects were attributed to infarction of the globus pallidus as later demonstrated by Mettler, Cooper, Liss, Carpenter and Noback (1954). This operation was, however, soon given up in favour of more certain and less risky methods of attacking the