Posteroventral medial pallidotomy can provide long term relief from many of the debilitating symptoms of Parkinson's disease, but it does not improve others and is not without side effects, according to a study by physicians at the University of Toronto, Canada (New England Journal of Medicine 2000:342;1708-14).
Pallidotomy is a surgical procedure in which overactive dopaminergic neurons in a portion of the basal ganglia, the globus pallidus, are ablated in an effort to reduce the tremors and dyskinesias of Parkinson's disease.
The procedure was developed in Sweden by Dr Lars Leksell in the 1950s but was abandoned in the 1960s after the introduction of levodopa for treating the disease. However, with the realisation that the response to levodopa in Parkinson's disease tends to wear off and in itself can produce dyskinesias, pallidotomy gained renewed acceptance as a treatment if the disease proved refractory.
Several hundred patients have undergone the procedure and have benefited from short term symptom relief. Few studies, however, have followed patients beyond two years.
The University of Toronto's researchers, led by Dr Jennifer Fine, followed 20 patients who underwent unilateral pallidotomy between 1993 and 1996. The group (15 men and 5 women, with a mean age of 57 (range 45-69) years was followed up for an average of 52 months (range 41-64 months). The patients had had symptoms of Parkinson's disease for an average of 12 years.
Serial postoperative assessments of the patients were taken both while the patients were taking anti-Parkinson's drugs and after an overnight withdrawal of the drugs.
The assessments were performed according to the unified Parkinson's disease rating scale (UPDRS), which scores motor function and abilities to carry out everyday activities.
The researchers found that pallidotomy was effective mainly in relieving contralateral symptoms of dyskinesia, bradykinesia, and tremor and that these improvements were most pronounced after an overnight withdrawal of the drugs. Initial improvements in activities of daily living were not sustained.
They report significant improvements in the UPRDS scores for contralateral tremor (65.4% improvement, P=0.007), rigidity (43.2% P=0.03), and bradykinesia (18.2% P=0.04).
The scores for contralateral dyskinesias for the period when patients were taking anti-Parkinson's drugs were also improved, by 70.6% (P<0.001), but other symptoms during this period were unaffected. The improvements in motor function were sustained for up to 5.5 years.
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Michael J Fox, who has Parkinson”s disease, waits to testify to a Senate committee