Before the advent of l-dopa, there was little treatment for Parkinson’s Disease. Clinicians had recognized that PD patients who developed a stroke in the basal ganglia stroke occasionally had improvements in their Parkinsonian symptoms. Neurosurgeons therefore attempted to induce basal ganglia strokes in PD patients. The results were unpredictable and complications were frequent and severe. Initially the pallidum became the favoured target and the operation, designed to make a small hole in it, was called the pallidotomy. Wycis and Spiegel reported that tremor was reduced in 78 percent of PD patients following pallidoansotomy. Reports of reduced tremor and improved rigidity after pallidotomy followed from the United States, Japan and Sweden. Fewer pallidotomies were performed after the introduction of l-dopa in the 1960s and the realization that thalamotomy was better at tremor reduction than pallidotomy. A Swedish report highlighting their results for PD patients following pallidotomy in the posteroventral pallidum (a slightly different target than the previous standard) was published in 1992. This led to a resurgence of interest in pallidotomy. This new found interest was bolstered by animal models which suggested Parkinson-like symptoms in primates were due to overactivity of the pallidum (inhibiting the motor thalamus) and that lesioning the overactive pallidum improved these symptoms. A number of well design prospective studies on the effects of pallidotomy were published in the 1990s. Pallidotomy was a very common operation in the 1990s (we performed over 250 at Vancouver General Hospital) but has been much less common following the introduction of deep brain stimulation.
Pallidotomy is currently performed at VGH for patients with dyskinesia interfering with their quality of life. A left sided pallidotomy would be expected to reduce dyskinesia on the entire right side of their body by approximately 90%. Following pallidotomy, patients remain on their PD medications to help their bradykinesia. In fact, their medications can be increased (to help their bradykinesia) without causing dyskinesia. There is also some improvement in bradykinesia, PD related pain, sleep and some weight gain after pallidotomy. We have only performed unilateral (one side only) pallidotomy because the risk of complication increases dramatically with bilateral (both sides) procedures.
The risks of pallidotomy include a rare chance of stroke (approximately 1%) and a rare chance of one sided weakness or visual field defect (reduced vision towards one side). Although these complications may be mild for the general public, they can be devastating for an already compromised patient with Parkinson’s disease. If patients have bilateral symptoms, they should consider deep brain stimulation (which can be done bilaterally).