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Alois A. Obwegeser, Ryan J. Uitti, John A. Lucas, Robert J. Witte, Margaret F. Turk and Robert E. Wharen Jr.

Object. The authors studied neuropsychological performance following microelectrode-guided posteroventral pallidotomy in patients with Parkinson's disease (PD) and evaluated correlations with presurgical and surgical factors.

Methods. Neuropsychological changes 3 months (43 patients) and 12 months (27 patients) after microelectrode-guided pallidotomy for PD are reported in a series of 44 consecutive patients with the disease, who improved neurologically, as measured by the Unified Parkinson's Disease Rating Scale (UPDRS) in both the “off” (p < 0.001) and best “on” (p < 0.001) states.

Findings of the vocabulary subtest of the Wechsler Adult Intelligence Scale—Revised (p < 0.01), Letter Fluency (p < 0.001), Verbal Fluency for semantic categories (p < 0.001), and the Wisconsin Card Sorting Test (p < 0.01) showed a significant decline in neuropsychological performance in patients 3 months after undergoing left-sided pallidotomy. Impairment in the language domain (semantic fluency) persisted at the 12-month follow-up examination (p < 0.01). Visual memory improved after right-sided pallidotomies (p < 0.01 after 3 months), with a nonsignificant trend toward persistent improvement 1 year postsurgery (p < 0.02 after 12 months). Preoperative semantic fluency was influenced by patient age (p < 0.001) and by the width of the third ventricle (p < 0.05), as measured by magnetic resonance imaging.

A regression model revealed that semantic fluency 3 months postoperatively was significantly affected by the baseline score (p < 0.001), side of surgery (p < 0.001), handedness (p < 0.01), and patient age (p < 0.05). However, postoperative lesion volume, lesion location, number of tracks, number of lesions, distance from anatomical landmarks, or UPDRS score did not significantly contribute to neuropsychological outcome.

Conclusions. Neuropsychological changes in a cohort of patients with PD who underwent pallidotomy and experienced excellent clinical benefits and minimum postoperative complications, emphasize the importance of neuropsychological examinations and further investigation of predictive factors.

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Jerzy L. Slowinski, John D. Putzke, Ryan J. Uitti, John A. Lucas, Margaret F. Turk, Bruce A. Kall and Robert E. Wharen


The object of this study was to assess the results of unilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) for management of advanced Parkinson disease (PD).


A clinical series of 24 patients (mean age 71 years, range 56–80 years) with medically intractable PD, who were undergoing unilateral magnetic resonance imaging–targeted, electrophysiologically guided STN DBS, completed a battery of qualitative and quantitative outcome measures preoperatively (baseline) and postoperatively, using a modified Core Assessment Program for Intracerebral Transplantations protocol.

The mean follow-up period was 9 months. Statistically significant improvement was observed in the Unified Parkinson's Disease Rating Scale (UPDRS) Part II score (18%), the total UPDRS PART III score (31%), the contralateral UPDRS Part III score (63%), and scores for axial motor features (19%), contralateral tremor (88%), rigidity (60%), bradykinesia (54%), and dyskinesia (69%), as well as the Parkinson's Disease Quality of Life questionnaire score (15%) in the on-stimulation state compared with baseline. Ipsilateral symptoms improved by approximately 15% or less. Performance on the Purdue pegboard test improved in the contralateral hand in the on-stimulation state compared with the off-stimulation state (38%, p < 0.05). The daily levodopa-equivalent dose was reduced by 21% (p = 0.018). Neuropsychological tests revealed an improvement in mental flexibility and a trend toward reduced letter fluency. There were no permanent surgical complications. Of the 16 participants with symmetrical disease, five required implantation of the DBS unit on the second side.


Unilateral STN DBS is an effective and safe treatment for selected patients with advanced PD. Unilateral STN DBS provides improvement of contralateral motor symptoms of PD as well as quality of life, reduces requirements for medication, and possibly enhances mental flexibility. This method of surgical treatment may be associated with a reduced risk and may provide an alternative to bilateral STN DBS for PD, especially in older patients or patients with asymmetry of parkinsonism.