Aggressive behavior as a rare side effect of subthalamic stimulation in Parkinson's disease

Although deep brain stimulation (DBS) has a well-established position in the treatment of Parkinson's disease (PD), it may be accompanied by different side effects including behavioral changes. We present a patient with advanced PD after bilateral stimulation of the subthalamic nucleus (STN) who developed attacks of aggressive behavior. The patient with a 12 year history of PD underwent the procedure of DBS with one-stage bilateral stereotactic approach using the Leksel G stereotactic frame. For STN identification microrecording technique was applied (5 microelectrodes). Four weeks after surgery STN stimulation was switched on. With increasing the amplitude of stimulation on the right (active contacts 1 and 2) the patient experienced transient episodes of aggression. Change of stimulation mode led to withdrawal of all side effects. We hypothesize that aggression episodes in the patient were caused by stimulation of limbic circuit probable within STN although we cannot exclude simultaneous stimulation of neighboring structures. Aggression episodes are rare side effect of STN-DBS, nevertheless they may be expected in more posteromedial placement of the electrode within STN. The presented case extends the evidence for non-motor functions of STN and highlights its role as an integrating structure within the basal ganglia system.