Surgery for Parkinson's disease.

Current pharmacological treatments for Parkinson's disease are not entirely adequate. A high proportion of patients chronically treated with levodopa and other dopaminergic drugs develop motor complications (fluctuations and dyskinesiae) and psychiatric complications.1 2 Additionally, some specific motor functions such as gait, balance, speech, deglutition, etc, become less responsive as disease and duration of treatment increase. It seems that both "non-physiological" dopaminergic stimulation and disease progression simultaneously interact to induce such complications.2 Xs a result, newer therapeutic avenues continue to be explored with two major aims: (1) to stop or slow down progression of disease and (2) to treat symptomatically the complications associated with chronic drug therapy. There has been a resurgence of interest in surgical treatments. Current stereotactic surgical techniques for Parkinson's disease include thalamotomy, pallidotomy, chronic intracerebral stimulation, or deep brain stimulation and striatal grafting of dopaminergic fetal tissue. Grafting is still under evaluation4 and is excluded from this review. The recent attention to surgical approaches has occurred as a result of several factors. Firstly, studies using the model of parkinsonism induced by 1-methyl-4-phenyl1, 2, 3, 6-tetrahydropyridine (MPTP), particularly in monkeys, have shown that hyperactivity in the subthalamic nucleus (STN) and medial globus pallidum (GPm) is a hallmark of the parkinsonian state and that lesions of these nuclei can reverse all the signs of experimental parkinsonism.6 Secondly, stereotactic surgery has become more precise and safer due to better stereotactic frames which provide high levels of mechanical accuracy, and to the development of high resolution brain CT and MRI. Finally, more refined electrophysiological techniques have allowed on line intraoperative assessment leading to precise recognition and mapping of the desired target and neighbouring structures-for example, the internal capsule or optic tract.