Predictors of neuropsychological outcome in patients following microelectrode-guided pallidotomy for Parkinson's disease

Object. The authors studied neuropsychological performance following microe lectrode-guided posteroventral pallidotomy in patients with Parkinson's dis ease (PD) and evaluated correlations with presurgical and surgical factors. Methods. Neuropsychological changes 3 months (43 patients) and 12 months (2 7 patients) after microelectrode-guided pallidotomy for PD are reported in a series of 44 consecutive patients with the disease, who improved neurolog ically, 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 semanti c categories (p < 0.001), and the Wisconsin Card Sorting Test (p < 0.01) sh owed 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 fluen cy 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 surge ry (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 signifi cantly contribute to neuropsychological outcome. Conclusions. Neuropsychological changes in a cohort of patients with PD who underwent pallidotomy and experienced excellent clinical benefits and mini mum postoperative complications, emphasize the importance of neuropsycholog ical examinations and further investigation of predictive factors.