Abstract 018: External carotid artery Pseudo aneurysm induced Internal Carotid Artery compression causing acute ischemic stroke
Authors: Kaur Harsimran , Singh Romil , Cerejo Russell 
Published: March 2024

Introduction
Here, we describe a patient in whom ischemic stroke was caused by compression of the Internal Carotid Artery (ICA) by a Pseudoaneurysm (PSA) of the External Carotid Artery (ECA) after Gun Shot injury. Eventually, the PSA of the Internal maxillary artery (IMAX) was embolized, resulting in resolution of the patient's symptoms.

Methods
Case Report

Results
A 75‐year‐old male with a history of atrial fibrillation on Eliquis presented to the emergency department after sustaining a gunshot wound to the left face. He had extensive injuries through the left masticator and submandibular space with an inferior orbital wall fracture. A Computed Tomography Angiography (CTA) neck showed injuries to the left proximal IMAX with a small PSA. As the PSA was asymptomatic it was managed with observation. On HOD day 13, CTA was done for a brief period of unresponsiveness, which showed high‐grade narrowing of left cervical ICA due to extrinsic compression from PSA which was supplied by a branch of the left ECA with distal re‐constitution (image A). The next day, patient developed right sided plegia and aphasia with NIHSS of 17. A CT head showed no acute intracranial abnormality. The patient underwent emergent Digital Subtraction Angiography (DSA), which demonstrated occlusion of the left cervical ICA from compression from a left IMAX PSA which was treated with n‐butyl‐cyanoacrylate TRUFILL embolization with resolution of flow limitation in the left cervical ICA (Image B1,B2). After embolization, the patient was oriented and able to lift right arm and leg anti‐gravity. Magnetic Resonance Imaging (MRI) was contraindicated due to retained bullet fragments. Repeat CT head did not show stroke.

Conclusion
A Pseudo aneurysm is characterized by a rupture of the arterial wall and the formation of an aneurysmal sac by the adjacent structures while the sustaining artery remains intact. The most prevalent causes are penetrating or acute blunt neck trauma, hyperextension injury, and injury to the base of the skull (1). Predisposing factors for PSA include carotid endarterectomy or a late complication of carotid artery dissection, infection, radiotherapy, and malignancy (1‐2). Cox et al. reported 124 patients with significant neck and head penetrating injuries. Eleven patients were found to have thirteen head and neck PSA: two in the ICA, one in the vertebral artery, and ten involving branches of the ECA. Two of seven symptomatic PSAs manifested with episodes of massive hemorrhage (3). There have been case reports describing the consequences of an elongated styloid process causing an ischemic stroke due to subsequent dissection and PSA formation (4).
According to our knowledge, this case report is one of the first to describe acute ischemic symptoms resulting from ECA PSA‐induced ICA compression, with resolution of symptoms following PSA embolization. The educational value of our case lies not only in the rarity of the condition but also in the uniqueness of its presentation. This case is a fundamental addition to the existing literature on rare neuro‐vascular anomalies leading to potential catastrophic outcomes.