Mycotic innominate artery pseudoaneurysm presenting as an embolic stroke

Abstract

Clinical Summary A 62-year-old man presenting with hoarseness was diagnosed with a squamous epithelial cell tumor of the soft palate. He underwent soft palate resection with adjuvant localized radiation therapy. After he was free of recurrence during the ensuing 5 years, osteoradionecrosis of the medial left clavicle and a corresponding methicillin-resistant Staphylococcus aureus (MRSA) infection involving the sternoclavicular joint developed. This was successfully treated with intravenous antibiotics, surgical debridement, and coverage with a left pectoralis muscle rotation flap. Four months after being treated for this infection, the patient had an embolic cerebrovascular accident localized to the right middle cerebral artery territory, as determined by magnetic resonance imaging, and this manifested as a left-sided hemiparesis. Incidentally, magnetic resonance imaging also revealed a 3.6 3.4-cm saccular pseudoaneurysm with a narrow 5-mm neck emanating from the anterior base of the innominate artery (Figure 1) and extensive inflammatory soft tissue in the anterior mediastinum extending from the left distal clavicle to the innominate, subclavian, and common carotid arteries. The results of blood cultures were positive for MRSA, and intravenous vancomycin was initiated. Because the results of additional diagnostic studies, including a carotid Duplex ultrasound and cardiac echocardiogram, were unremarkable, the most plausible source of this embolic stroke was ascribed to the pseudoaneurysm. Because of the perceived risk of further embolic stroke and risk of rupture, pseudoaneurysm resection was recommended. Surgical resection was performed 2 weeks after the cerebrovascular accident and after near-complete recovery of left-sided motor function. At the time of the operation, the innominate artery pseudoaneurysm was identified through a standard median sternotomy approach (Figure 2). During the dissection, moderate inflammatory tissues were encountered in the vicinity of the aortic arch in continuity with the left sternoclavicular region, although no gross purulence was noted. Cardiopulmonary bypass was instituted with aortic cannulation of the distal ascending aorta and dual-staged venous cannulation of the right atrium. With the use of deep hypothermic circulatory arrest, the pseudoaneurysm was dissected circumferentially and opened. Substantial thrombus was removed from the saccular component of the pseudoaneurysm, revealing a narrow neck arising approximately 8 mm distal to the origin of the innominate artery. After the pseudoaneurysm was completely resected, the resultant 1-cm defect at the base of the innominate artery was repaired with a patch of autologous pericardium fixed in glutaraldehyde. A 28-minute period of circulatory arrest was required. The results of intraoperative cultures and histologic analyses of the pseudoaneurysm and surrounding mediastinal tissues were negative for active infection or neoplasm. The patient was discharged to home after an unremarkable 7-day postoperative course to complete a 6-week course of MRSAspecific intravenous antibiotics.