S117. Intraoperative detection of posterior circulation transient ischemic attack: Single case study

Abstract

Introduction Intraoperative Neuromonitoring (IONM) has been utilized to aid in the prevention of iatrogenic injury. Studies have described the role IONM may play in predicting post procedural neurological deficits (PPNDs). Here we discuss a unique case study of a patient who underwent stent-assisted embolization of a large basilar tip aneurysm with very specific localizing changes observed by analysis of somatosensory evoked potentials (SSEPs), electroencephalography (EEG), and brainstem auditory evoked potentials (BAEPs). Methods A 66 year old female with past medical history of hypertension and hyperlipidemia presented to the emergency department (ED) with photophobia and a left dilated pupil. MR angiography revealed a large basilar tip aneurysm. Aspirin and Plavix were administered and a stent-assisted coil embolization was performed with complete resolution of symptoms. Follow-up elective repair of the aneurysm was scheduled. Prior to the follow-up elective repair, the patient presented to the ED once again with a new onset headache and anisocoria. MR angiogram was performed which revealed no acute changes. The patient was admitted and underwent further embolization of the aneurysm from the left P1 into the basilar apex. The initial stent was deployed with no complications. During advancement of a second stent, abrupt cortical amplitude decreases of 76% and 79% in the left upper and lower extremity traces, respectively, were observed. All other traces remained stable. Catheter placement was inspected and noted as normal. Signals began to improve and returned to baseline in less than 10 min as the procedure was completed without placement of an additional stent. Results Six days post-operatively, the patient presented to an outside ED complaining of posterior headache and left-sided paresthesia in the trigeminal nerve distribution. She was transferred to the University of Michigan for further evaluation. MR imaging was unremarkable but further workup revealed sub-therapeutic Plavix levels so her dose was increased. Her symptoms resolved within 24 h. Conclusion We hypothesize that both intraoperative electrophysiological changes and PPNDs reflect a specific ischemic event in the P1/P2 deep perforator distribution affecting the right ventral posterolateral and posteromedial nuclei of the thalamus, respectively. This case highlights the potential anatomic specificity of multimodal IONM by the changes seen at the time of manipulation of the perforating branches of the posterior circulation, correlating with subsequent TIA and symptoms attributable to the same vascular distribution. This interpretation must be taken with caution as this does not establish a direct correlation of IONM changes with subsequent TIA. Potential correlation should be studied in a larger population undergoing endovascular intervention in the posterior circulation.