Tremor control after pallidotomy in patients with Parkinson's disease: correlation with microrecording findings

The goals of this study were to analyze the effect of pallidotomy on parkinsonian tremor and to ascertain whether an association exists between microrecording findings and tremor outcome. Forty-four patients with Parkinson's disease who had drug-induced dyskinesia, bradykinesia, rigidity, and tremor underwent posteroventral pallidotomy. Using a 1-mu-tip tungsten electrode, microrecordings were obtained through one to three tracts, starting 10 mm above the pallidal base. Tremor severity was measured on a patient-rated, 100-mm Visual Analog Scale (VAS), both preoperatively and 3 to 9 months (mean 6 months) postoperatively. Preoperatively, tremor was rated as 50 mm or greater in 24 patients (55%) and as less than 25 mm in 13 patients (30%). Postoperatively, tremor was rated as 50 mm or greater in five patients (11%) and less than 25 mm in 29 patients (66%). The difference was significant (p = 0.0001). Four patients (9%) had no postoperative tremor. Tremor improved by at least 50% in eight (80%) of 10 patients in whom tremor-synchronous cells were recorded (Group A) and in 12 (35%) of 34 patients in whom tremor-synchronous cells were not recorded (Group B). This difference was significant (p = 0.03). Tremor improved by at least 50 mm in all (100%) of the seven Group A patients with severe (> or = 50 mm) preoperative tremor and in nine (53%) of 17 Group B patients with severe preoperative tremor. This difference was also significant (p = 0.05). The authors prefer two conclusions: 1) after pallidotomy, tremor improves by at least 50% in two-thirds of patients with Parkinson's disease who have severe (> or = 50 mm on the VAS) preoperative tremor; and 2) better tremor control is obtained when tremor-synchronous cells are included in the lesion.