Neuropsychological consequences of posteroventral pallidotomy for the treatment of Parkinson's disease

Objective: Neuropsychological changes were assessed in patients who had idiopathic PD after unilateral posteroventral pallidotomy. Methods: Posteroventral stereotactic pallidotomies were performed on 42 PD patients (24 right and 18 left hemisphere). All patients were evaluated in the "on state" before the procedure (n = 42) and at intervals of 3 (n = 26), 6 (n = 27), and 12+ (n = 24) months after surgery. Results: Modest improvement in sustained attention and decline in working memory was observed by 6 months after surgery. Left hemisphere lesions led to a loss of verbal learning (-2.2 SD) and verbal fluency (-1.6 SD) in 60% of patients at their first evaluation at 3 or 6 months. No patients returned to baseline on the verbal fluency task and most (71%) did not recover verbal-learning ability by 12 months after surgery. Right hemisphere lesions led to a loss of visuospatial constructional abilities (-3.5 SD), which fully resolved by 12 months for all but one patient. Evidence of further decline of frontal-executive functioning was noted within other tasks but not on a "direct" test (i.e., Conditional Associative Learning). Lastly, behavioral changes of a "frontal nature" were reported in 25% to 30% of patients. These cognitive and emotional costs increased dependence in these domains and negatively affected some patients' relations with caregivers and restricted their ability to function properly at work or in social settings. Caregivers, particularly, and patients who were aware of their resulting changes had difficulty adjusting after surgery. Conclusions: Although patients and caregivers were generally pleased with the clinical neurologic outcome of the procedure, the neurologic benefits of unilateral pallidotomy must be weighed against modest cognitive and behavioral risks.