Subclavian Pseudoaneurysm Mimicking Recurrent Head and Neck Cancer

True and false aneurysms of the subclavian artery are extremely rare and are most often due to penetrating trauma¹ ; however, they have also been associated with thoracic outlet syndrome, congenital abnormalities, cystic medial necrosis, Marfan syndrome, Turner syndrome, and mycotic infections such as syphilis and tuberculosis.^{2 - 3} External beam radiation therapy has been shown to produce early and delayed injury to arterial vessels. The vessels reported to rupture most frequently from radiation-induced damage are the carotid, aorta, and femoral arteries.⁴ The formation of a pseudoaneurysm in the subclavian artery due to radiation therapy alone has not been reported. We present a case of a right subclavian pseudoaneurysm likely caused by radiation injury that mimicked recurrent head and neck carcinoma 4 years after surgical extirpation and radiation treatment for squamous cell carcinoma of the tonsil. In addition, we review the diagnostic evaluation and surgical control of the subclavian artery.

A 50-year-old man underwent a right hemiglossectomy, tonsillectomy, and neck dissection, and required a pectoralis flap for T3 N1 M0 squamous cell carcinoma of the tonsil followed by radiation of 59.4 Gy to the primary field and 50.4 Gy to the neck via opposed lateral ports. The patient was observed without evidence of recurrent disease for 2 years and then was lost to follow-up for 2 years. He subsequently presented to the emergency department because of progressive hoarseness for 2 months, dysphagia for 2 weeks, and paresthesia in his right arm. On examination, the patient was afebrile, orthostatic, cachectic, had a palpable fullness in the right side of the neck without pulsation or bruit, a sluggish right vocal cord, and decreased sensation in the right radial and median nerve distribution despite full strength. The patient's hematocrit level was 0.47. A computed tomographic scan of the neck showed multiple low-density lesions throughout the neck that were suspicious for malignant disease (Figure 1). Findings from an esophagoscopy revealed an extrinsically compressing mass in the cervical esophagus without mucosal involvement. Multiple fine-needle aspirates of the upper aspect of the neck were nondiagnostic, revealing only necrosis. The patient was taken to the operating room for open biopsy. Several frozen-section incisional biopsies were performed, yielding a diagnosis of necrosis with no evidence of malignancy. Another biopsy was then performed to try to determine a diagnosis, but the patient had sudden torrential bleeding, requiring emergency median sternotomy with supraclavicular and infraclavicular approaches when exposure of the carotid artery did not reveal the bleeding source. Control of the innominate, carotid, and vertebral arteries and thyrocervical trunk was accomplished after proximal and distal subclavian control resulted in persistent back bleeding. Ligation of the right subclavian artery was necessary to control the subclavian pseudoaneurysm. Biopsy specimens of all tissue were negative for malignancy, and cultures revealed no organisms. The patient later required an omental free flap with a split-thickness skin graft for vessel coverage. Four years later, the patient is still alive without recurrent local disease or evidence of upper extremity ischemia. His wounds have healed well; however, his brachial plexopathy is permanent.

Subclavian pseudoaneurysms are extremely rare in the absence of penetrating trauma.⁵ Aneurysmal disease of the subclavian artery has also been associated with congenital malformations, thoracic outlet syndrome, atherosclerosis, Marfan syndrome, cystic medial necrosis, and mycotic infections such as syphilis and tuberculosis.^{2 - 3} Typically, pseudoaneurysms in the head and neck will present with a hard sign of vascular injury such as a pulsatile mass, palpable thrill, bruit, or evidence of regional ischemia. However, a review of cases of penetrating trauma to the base of the neck revealed that 32% of patients with vascular injuries in this region presented with no diagnostic signs.⁶ In retrospect, the patient's brachial plexus paresthesia was the only hard physical sign of vascular injury, which was initially attributed to tumor invasion. Close inspection of the computed tomographic scan revealed a small region with a crescent-shaped high signal in the area adjacent to the right subclavian artery that was suspicious for layered, extravasated contrast and false lumen tracking (Figure 2). This sign had not been previously appreciated in light of the multiple other areas of higher-signal ring enhancement throughout the neck. Weissman et al⁷ report 2 cases of thrombosed carotid artery aneurysms mimicking head and neck tumors that demonstrated low attenuated masses with enhancing rims. The proximity of these masses to the carotid artery warranted further evaluation, eventually leading to the diagnosis. In the absence of thrombus, computed tomographic scans often show a region of contrast enhancement in areas of aneurysmal dilation or vascular disruption. Thrombotic or nonthrombotic plaque-filling aneurysmal dilations often have a crescent appearance of varying intensity depending on the composition of the debris. In the event that an aneurysm or pseudoaneurysm is suspected, an evaluation should include angiography to determine the extent of vascular pathologic injury and collateral blood supply. Because a vascular lesion had not been suspected in our patient, direct vascular imaging had not been performed.

Control of torrential bleeding in the head and neck may necessitate proximal control in the mediastinum if exposure and control of the carotid and vertebral arteries are unsuccessful. The chest and femoral regions should be prepared in the event that cardiopulmonary bypass becomes necessary. The innominate vessels, ascending aorta, and right-sided intrathoracic subclavian artery can be approached through a median sternotomy that can be extended into supraclavicular and carotid artery incisions (Figure 3). The subclavian artery can be further exposed with clavicular resection. The left subclavian artery can be accessed through a high anterolateral thoracotomy as well as supraclavicular incisions.⁸ Vessel reconstruction can be attempted to restore distal flow through the injured vessel. A variety of techniques of vessel reconstruction have been described, including primary repair, interposition or aortic arch grafting, as well as extra-anatomical bypass, such as carotid-subclavian transposition and axilloaxillary grafts.⁹ Given our patient's history of irradiation of this area, the large exposed wound requiring delayed flap closure, and the large segment of destroyed vessel, we elected to ligate the subclavian artery. Although isolated cases of upper limb ischemia and gangrene have been reported due to subclavian artery ligation, series of subclavian artery aneurysms treated with ligation have reported only arm claudication as a result of not revascularizing the vessel.¹⁰ In a review of 971 subclavian artery ligations for Blalock-Taussig shunts, only 2 patients developed upper extremity ischemia and gangrene.¹¹

Radiation-induced vascular injury has been well documented, with the carotid, aorta, and femoral arteries reported as those most likely to rupture⁴ ; however, no cases of radiation-induced pseudoaneurysms of the subclavian artery have been reported to date. McCready et al¹² review 20 cases of radiation-induced arterial injuries and note 2 patterns of damage: arterial disruptions are more common in the carotid arteries of patients with head and neck cancer and tend to present early (<20 weeks) relative to the time of radiation, whereas arterial stenosis or occlusion tends to occur later (after months or years). Fonkalsrud et al¹³ analyzed the effect of irradiation on a dog's femoral arteries and noted acute-phase injury (in <48 hours) consisting of endothelial disruption with patchy intimal fibrin deposition. The effects of irradiation, which were not seen in the media or adventitia until several weeks after radiation treatment, included decreasing muscular cellularity and progressive fibrosis, which constricted the vessels, leading to accelerated atherosclerosis. Reported responses to irradiation include intimal thickening with alteration of internal elastic lamina by hyaline swelling, fragmentation, beading, and foam-cell plaques within the subintima.^{14 - 15}

We can only speculate that our patient's lesion was predominantly the result of radiation-induced injury. The influence of the patient's previous surgery and any preexisting atherosclerotic disease cannot be discerned. In a review of 10 patients with major vessel rupture after radiation therapy, Fajardo and Lee⁴ conclude that local factors such as previous surgery, fistula formation, and infection are important in the progression of radiated vascular injury to blowout. Our patient had not shown any clinical signs of fistula formation after his original surgery; however, subclinical infection and contamination of the neck may have played a role in vessel damage. The patient's original tumor did not involve lymph nodes in the base of the neck, making direct tumor extension with weakening of the vessel a less likely source. Iatrogenic pseudoaneurysms of the subclavian artery have been reported as a result of central venous line placement; however, these complications are typically evident at the time of line placement.¹ Because our patient had a pectoralis major flap reconstruction of his pharyngeal defect, no subclavian lines had been placed in this region to account for vessel injury, and none of the patient's fine-needle aspirations were performed in the base of the neck.

Rupture of major head and neck vessels often results in death if prompt intervention is not instituted, and surgery to control the bleeding may result in marked neurologic impairment. Our case was extremely unusual since to our knowledge no previous cases of subclavian pseudoaneurysms induced by radiation therapy have been reported. The patient's history of surgery for head and neck carcinoma, the lack of overt bleeding, and the absence of hard signs of vascular injury and subtle radiographic signs made diagnosis difficult prior to surgery. This diagnostic dilemma led to aggressive emergency surgical care. One must recognize the possibility of uncontrolled bleeding in the neck arising from mediastinal vessels and be aware of surgical approaches to the thoracic inlet.

Accepted for publication June 10, 1998.

We would like to thank Patsy Bryan, MS, for her assistance in preparing the illustrations in this article.