Functional and dysfunctional impulsivities changes after deep brain stimulation of the subthalamic nucleus

We investigated changes of impulsivity after deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) patients, distinguishing functional from dysfunctional impulsivity and their contributing factors. DBS-STN is routinely used to treat motor complications in PD [1] . However, its impact on impulsivity in PD patients is controversial [2] , [3] , [4] . Data of 33 PD patients treated by DBS-STN were studied before and 6 months after surgery: motor impairment, medication (dose and dopaminergic agonists), cognition, mood and occurrence of impulse control disorders. Impulsivity was assessed by the Dickman scale, which distinguishes functional impulsivity (FI), reflecting the potential for reasoning, premeditation and rapid action when the situation requires it, and dysfunctional impulsivity (DFI), reflecting the lack of prior reasoning, even when the situation demands it. The location of DBS leads was studied on postoperative MRI using a deformable histological atlas and by compartmentalization of the STN. After DBS-STN, dysfunctional impulsivity was significantly increased (mean pre- and postoperative DFI scores 1.9 ± 1.6 and 3.5 ± 2.4, P  Our study suggests that DBS-STN may have a different impact on both dimensions of impulsivity, worsening pathological impulsivity without altering physiological impulsivity. The increase in dysfunctional impulsivity may be favoured by the location of the electrode in the ventral, limbic, part of the STN.