Impulse control and related behaviors after bilateral subthalamic stimulation in patients with Parkinson's disease

The effect of subthalamic nucleus deep brain stimulation (STN DBS) on impulse control and related behaviors (ICRB) in patients with Parkinson's disease (PD) is conflicting. We evaluated ICRB before and after bilateral STN DBS in patients with PD. A total of 89 patients with PD treated with bilateral DBS of STN underwent retrospective assessment of ICRB before and after DBS. Of the 89 patients studied, 20 patients (22.5%) had ICRB in the preoperative period. In 13 of those 20 patients (65%), preoperative ICRB improved, including resolution in six patients. Nine patients developed de novo ICRB after DBS, thus 23 patients (25.8%) had ICRB in the postoperative period. There was no demographic difference between the patients with or without ICRB in the preoperative state. In the postoperative state, the patients with ICRB had higher levodopa equivalent daily dose (LEDD) levels and lower Mini-Mental State Examination (MMSE) scores than the patients without ICRB. However, postoperative worsening or de novo ICRB did not correlate with LEDD levels or MMSE scores. Severity of ICRB worsened more after DBS in older patients. Patients with worsened or de novo ICRB after surgery had a greater decrease in Beck Depression Index scores after surgery compared with patients whose ICRB improved. In conclusion, ICRB may resolve or improve, or new ICRB may appear, after bilateral STN DBS. The difference in risk factors for preoperative vs. postoperative ICRB suggests that the pathogenesis of those conditions is different, at least in part.