Intraparenchymal cyst development after deep brain stimulator placement.

Following deep brain stimulation (DBS) surgery, a variety of potential mechanical or functional complications ranging from perioperative events to hardware malfunction may occur. We present 2 patients who developed a unique complication of cyst formation at the tip of the DBS electrode in the absence of infection. One patient had a unilateral ventral intermediate lead placement for essential tremor, and the other had bilateral subthalamic nucleus (STN) placement for Parkinson's disease. After a period of symptom control, at 3 and 8 months after surgery, respectively, both patients developed new neurological deficits and were found to have a cyst at the left DBS lead tip. The right lead in the patient with the bilateral STN implant was without issue. Both affected leads were removed and the problematic symptoms regressed quickly over several days, though the lesion effect on the patients' initial tremor symptoms lasted for months. Bacteriological cultures of the removed electrodes and wounds were negative. We report a rare complication of DBS and show that simply removing the involved lead results in cyst resolution.