Behavioral effects of subthalamic deep brain stimulation in Parkinson's disease.

To date, few studies have utilized standardized measures to assess the neurobehavioral changes that can accompany deep brain stimulation (DBS) of the subthalamic nuclei (STN) for the treatment of Parkinson's disease (PD), yet behavioral changes are the most debated among practitioners. We evaluated behavior with the Frontal Systems Behavior Scale (FrSBe), which includes a large-scale normative sample for self- and collateral ratings and is particularly relevant to PD with subscales assessing Apathy, Disinhibition, and Executive Dysfunction. Data were collected from 16 (11 males) PD patients. All FrSBe subscale scores increased significantly when retrospective preoperative scores and current (postoperative) scores were compared. Self- and collateral FrSBe ratings were not significantly correlated with each other, though for both scores at least half of the group met criteria for a clinically significant level of symptoms postoperatively. No significant correlations were seen for collateral current FrSBE ratings with cognitive or motor variables. Higher self-ratings of behavior characteristic of apathy were related to higher self-ratings of depressive symptoms, and to a smaller decrease in antiparkinsonian medications following surgery. We propose that the standardized assessment of behavioral aspects of executive dysfunction adds information that is largely dissociable from the motor and cognitive assessment of function in PD patients undergoing STN DBS. In future, prospective standardized measurement of behavior may allow for better prediction of which patients will experience significant behavioral issues postoperatively.