Pallidotomy and deep brain stimulation of the pallidum and subthalamic nucleus in advanced Parkinson's disease

There has been a resurgence in the use of neurosurgical procedures for the treatment of Parkinson's disease (PD). Pallidotomy has become a widely performed procedure on the basis of reports which describe marked reduction of levodopa-induced dyskinesias and variable improvement in parkinsonism. Preliminary reports of the effects of globus pallidus internus (GPi) and subthalamic nucleus (STN) deep brain stimulation (DBS) have also been promising. Al 6-month follow up, a cohort of our first 40 patients undergoing pallidotomy demonstrated the following mean improvements when examined after drug withdrawal (off) and under optimal medication (on): total motor off scores-31%; total off activities of daily living scores-30%; and total on dyskinesias-63% (contralateral and ipsilateral dyskinesias improved 82% and 50%, respectively). Although improvements in contralateral dyskinesias and total off parkinsonism were sustained at 2-year follow up (N = 11), benefit for ipsilateral dyskinesias was lost after 1-year follow up (N = 24), and postural stability and gait improvements lasted only 3-6 months. On-period, levodopa-resistant symptoms did not benefit from pallidotomy. Mean improvements in 8 patients undergoing GPi DBS (4 unilateral and 4 bilateral) at 3 months were as follows: total motor off scores-27%; total off activities of daily living scores-26%; and total on dyskinesias-60%. At most recent follow up, 6 patients with STN DBS (5 bilateral and 1 unilateral) showed the following mean improvements: total motor off scores-41%; total motor on scores-27%; total off activities of daily living scores-40%; and total on dyskinesias-41%. Pallidotomy reduces dyskinesias and off disability. GPi DBS may have effects similar to pallidotomy, but might be safer when bilateral procedures are required. Bilateral STN DBS may improve off parkinsonism more than other procedures and might also improve on-period motor function. A randomized trial will be required to determine which procedure is most effective for patients with different clinical features.