Surgical treatment of Parkinson's disease.

Improved understanding of the pathophysiologic mechanisms underlying parkinsonian signs and symptoms, as well as refinement of methods and techniques in neurosurgery, neuroradiology and neurophysiology, have stimulated the current interest in and expanded the role of surgical treatment of Parkinson's disease. Pallidotomy and thalamotomy are the stereotactic procedures most commonly performed in patients who fall to obtain satisfactory relief of their symptoms despite optimal medical therapy. Small lesions disrupt the abnormal activity of basal ganglia circuitry. Other options currently being studied include chronic high-frequency stimulation and transplantation of fetal mesencephalic tissue. Chronic thalamic stimulation, involving permanent implantation of a deep brain electrode and a pulse generator, effectively controls contralateral tremor. Fetal nigral transplantation, which is still an experimental procedure, has the potential of restoring lost nigrostriatal pathway. The choice of treatment depends on the severity of the symptoms and their response, or lack of response, to pharmacologic therapy. With appropriate selection criteria, functional and symptomatic improvement can be achieved in most patients with Parkinson's disease who are treated with neurosurgical procedures. The long-term effects of these treatments, however, await the results of longitudinal studies.