Pallidotomy: a comparison of responders and nonresponders

We reviewed a prospective series of 32 unilateral, large-volume, microelectrode-guided posteroventral pallidotomies to determine the differences between responsive and nonresponsive patients. Our patients underwent extensive pre- and postoperative evaluations. One year postoperatively, we correlated the outcomes of 25 patients with their histories, physical findings, neuropsychological assessments, and lesion characteristics to further understand the indications, limitations, and pitfalls of unilateral pallidotomy. Our group judged responsiveness by comparing the preoperative total Unified Parkinson's Disease Rating Scale off-state scores with those obtained 1 year postoperatively. A score indicating greater than 20% improvement at 1-year follow-up was rated a good outcome; improvement of greater than 40% was rated an excellent outcome. Although most patients sustained long-term benefits, some demonstrated little or no improvement. Patient and lesion factors influenced outcome. Younger age (70 yr), absence of tremor, increased duration of disease, reduced responsiveness to L-dopa, frontal behavioral changes, prominent apraxic phenomena, and improper lesion placement predicted a poor response. Unilateral, large-volume pallidotomy with precise lesion control provides long-lasting benefits for carefully selected patients.