Incidental Finding of an Asymptomatic Perielectrode Cyst After Deep Brain Stimulation for Parkinson's Disease.

Implanted intracerebral devices can lead to infection, hemorrhage, or the formation of fluid-filled cysts. Formation of a perielectrode cyst after deep brain stimulation (DBS) has been reported in a limited number of patients. Additionally, diverse causes and clinical presentations have been associated with these cysts. We present a case of perielectrode cyst formation three months after implantation of a subthalamic nucleus DBS (STN-DBS) for Parkinson's disease (PD). A 59-year-old woman was diagnosed with PD in 2011. In November 2023, the patient underwent staged placement of an STN-DBS without perioperative complications. Immediate postoperative cerebral CT ruled out acute complications. Postoperatively, the patient showed clear clinical improvement, and a substantial reduction in the levodopa dose was achieved (1,500 mg/24 h vs. 250 mg/24 h). There was a significant change in neurocognitive testing three months postoperatively, with a decrease in the Montreal Cognitive Assessment score from 29/30 to 24/30. Follow-up cerebral MRI showed a perielectrode cystic lesion around the left electrode. The patient's clinical status and electrode impedances remained unchanged during follow-up. Serial imaging demonstrated gradual regression of the cyst. Perielectrode cysts after DBS can occur at different locations and at varying postoperative time points. They may present with diverse clinical manifestations or remain completely asymptomatic. Different putative mechanisms and treatment options have been described; however, the paucity of reported clinical cases makes it difficult to speculate on a primary cause.