Pseudoaneurysm Formation after Stereoencephalography for Epilepsy

Introduction: Stereoencephalography (SEEG) has emerged as the most common technique for invasive monitoring as part of the preoperative workup for epilepsy surgery. The use of intracranial implants has the potential for vascular injury giving rise to pseudoaneurysm, followed by unpredictable, delayed hemorrhage. Confirmed cases of post-SEEG pseudoaneurysm, as well as suspected cases involving delayed hemorrhage after explanation, are very rare and have not allowed identification of the inciting cause. Case Presentation: A patient was evaluated over the course of two SEEG implantations before the decision to proceed with deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) to treat their drug-resistant epilepsy. Preoperative imaging for DBS revealed a pseudoaneurysm proximal to an SEEG craniostomy site. The lesion was treated with excision and vascular bypass, and the patient ultimately underwent DBS as planned. Retrospective analysis strongly implicated the SEEG implantation in pseudoaneurysmal formation, most likely via arterial collision resulting from entry site deviation from the planned stereotactic trajectory. Conclusion: Pseudoaneurysm may be a more prevalent complication of SEEG than existing literature would suggest, as the delayed formation of these lesions can allow them to escape recognition on routine postoperative imaging. Though likely still uncommon, this may suggest the prudence of additional radiological surveillance. This complication is potentially devastating if unrecognized and untreated, but otherwise does not preclude further surgical therapies for epilepsy.