Aneurysms of the innominate, common carotid, and subclavian arteries are rare in comparison to occlusive disease of the same arteries. Kieffer, with the largest great vessel practice in the Western World, treated 27 innominate artery aneurysms over 27-years (one aneurysm per year). At the Massachusetts General Hospital, three innominate artery aneurysms were repaired over 20 years, during which time 71 occlusive lesions of the innominate artery underwent operation. Nineteen carotid artery aneurysms were reported over 7 years at the Mayo Clinic, whereas over that same period, 1,000 carotid endarterectomies were performed. At the Cleveland Clinic the ratio of carotid aneurysmal disease to occlusive disease was 1:250.

Brachiocephalic artery aneurysms are also rare in comparison to arterial aneurysms at other peripheral sites and are estimated to account for 0.4% through 4% of all aneurysms. Surgeons at Baylor-Houston encountered 37 carotid artery aneurysms among 8,500 aneurysms operated upon over 20 years. Subclavian artery aneurysms were found in only 2 of 57 patients with multiple aneurysms treated at the University of Michigan.

If aneurysms of the second and third parts of the subclavian artery, related to thoracic outlet syndrome with osseous, tendinous, or other mechanical obstruction at the thoracic outlet are included, the subclavian artery is the most frequently involved of the great vessels with aneurysmal degeneration, followed in frequency by the common carotid artery and lastly by the innominate artery. If such distal aneurysms are not included, aneurysms of the common carotid artery and the first part of the subclavian artery occur with the same frequency. By either method of inclusion, innominate artery aneurysms are the least commonly encountered of the brachiocephalic aneurysms. A 40-year review from the Mayo Clinic identified 73 great vessel aneurysms. Of those, 41 involved the subclavian artery, 25 involved the carotid artery, and six involved the innominate artery. There was one aneurysm of the vertebral artery. Within that group of 41 subclavian artery aneurysms, three were of aberrant right subclavian arteries. Sixteen of the 38 subclavian artery aneurysms (42%) treated at the Mayo Clinic were related to thoracic outlet compression, and 14 (37%) were related to degeneration.

Atherosclerosis, or degeneration, is the most frequently identified etiology of brachiocephalic aneurysms. Whether that represents a primary or secondary phenomenon is not known. Degeneration is less uniformly implicated for aneurysms of the brachiocephalic vessels than it is for aneurysms in other locations. In the above-mentioned series from the Mayo Clinic, it was felt to be the etiology in two-thirds of the innominate artery aneurysms, one-third of the subclavian artery aneurysms, and only 12% of the carotid artery aneurysms. Multiple other causes are encountered, especially for carotid and subclavian artery aneurysms, but also for innominate artery aneurysms. These include fibromuscular dysplasia, cystic medial necrosis, Ehlers-Danlos syndrome (EDS), traumatic and spontaneous dissection, Takayasu arteritis, syphilis, and infection. Although luetic aneurysms are rarely encountered today, Kieffer reported 5 in his series of 27 patients with innominate artery aneurysms.

Because of the various etiologies of great vessel aneurysms, including thoracic outlet syndrome, and because of the relative infrequency of degeneration as the sole predictable cause, brachiocephalic artery aneurysms are seen in a wide spectrum of young and old patients. In Bower’s review of these aneurysms, the mean age was 50.5 years with a range from 16 to 84 years. The mean age of patients with subclavian artery aneurysms was 51.7 (range from 17 to 82); the mean age of patients with common carotid artery aneurysms was 46.6 (range from 16 to 78); and the mean age of patients with innominate artery aneurysms was 56.8 years (range 34 to 75 years). There was a slight preponderance of men. The male-to-female ratio was 1:1.3 for patients with subclavian artery aneurysms (reflecting the predominance of women with thoracic outlet syndrome), 1.8:1 for patients with carotid artery aneurysms, and 5:1 for those with innominate artery aneurysms. In Ericson and Robb’s review of brachiocephalic artery aneurysms from South Africa, the mean age was 42 years, ranging from 18 to 75 years, and the male-to-female ratio was 1.9:1.

The great majority (67% to 75%) of patients with brachiocephalic artery aneurysms present symptomatically. Symptoms may be related to the aneurysm mass per se with its local effect on adjacent structures. The many structures of the mediastinum, neck, and thoracic outlet are neatly compacted in their confined spaces. Brachiocephalic artery aneurysms are, therefore, prone to present with symptoms related to the mass effect of the aneurysm on these adjacent venous, tracheal, esophageal, and nervous
structures. Such local symptoms are seen much more frequently with brachiocephalic artery aneurysms than with thoracic or abdominal aneurysms or with aneurysms at other peripheral sites. Patients may present with pain syndromes related to inflammation of adjacent somatic or autonomic nerves, seen as Horner syndrome, carotodynia, or other unusual variants of head and neck pain. Venous compression including superior vena cava syndrome has been described. Aberrant subclavian artery aneurysms notoriously present with obstruction of the trachea and/or esophagus, the latter symptoms termed dysphagia lusoria.

In addition to the local symptoms related to these large, intact, otherwise quiescent aneurysms, patients present with symptoms related to the vascular complications from these aneurysms. Thrombosis and embolization may give rise to transient ischemic attacks (TIAs) and strokes in both the carotid and vertebral artery distributions. Micro-embolization, frank gangrene, and tissue loss of the upper extremities are seen, and rupture is a very real risk for these patients, especially those with large or mycotic aneurysms. Aberrant subclavian artery aneurysms, as all embryonic aneurysms, are structurally weak and especially prone to aneurysmal degeneration. These aneurysms may rupture into the esophagus and are the only known cause of primary aorto-esophageal fistulas.

Great vessel aneurysms have an association with other brachiocephalic artery aneurysms and with arteries in other locations. Anywhere between one-fourth to one-half of these patients will have an additional aneurysm, most commonly seen in the thoracic or abdominal aorta and/or the femoral and popliteal arteries. An association is seen least commonly with aneurysms of the visceral arteries. Approximately 5% to 10% of patients presenting with a brachiocephalic aneurysm will have multiple great vessel aneurysms. This is especially true of patients with collagen vascular disorders such as Ehlers-Danlos syndrome. Ehlers-Danlos type IX patients may present with synchronous or metachronous peripheral aneurysms and later with thoracic and abdominal aortic aneurysms.

As is true of most disease states, a detailed history and physical examination are vital. Discovery of a mass in the neck or supraclavicular area with or without symptoms may be indicative of great vessel aneurysmal disease. The sudden appearance of painful, discolored bluish lesions in the hand and fingers could be indicative of brachiocephalic aneurysmal disease. Neurologic symptoms such as TIA or stroke with appropriate findings on physical exam may indicate a brachiocephalic artery aneurysm as the likely source of the problem. Patients presenting with cranial nerve dysfunction; unusual head, neck, or ear pain; carotodynia; Horner syndrome; obstructed breathing; or venous engorgement of the head, neck, or upper extremities should be evaluated for brachiocephalic artery aneurysms. The unusual pain syndromes are seen most commonly with aberrant subclavian artery aneurysms and with carotid artery aneurysms.

Ultrasound may be of some help in screening these patients, especially to differentiate tortuous carotid or subclavian vessels from true aneurysmal disease. Probably the most common brachiocephalic “aneurysms” vascular surgeons are asked to see in these locations are tortuous, ectatic common carotid and subclavian arteries that are easily visible and palpable. These can be diagnosed and differentiated from real aneurysms by ultrasound.

With brachiocephalic artery aneurysms, imaging studies are a necessity for diagnosis and operative planning. In the past, arch and four-vessel arteriography have been the sine qua non of diagnosis of these lesions. Currently, computed tomographic angiography (CTA) is used more and more. In the view of many clinicians, including this one, it is the diagnostic test of choice. CTA allows imaging not only of the flow lumen but also of the aneurysm dimensions and its relationship to adjacent structures in the neck and mediastinum. Magnetic resonance angiography (MRA) may be used for patients with renal insufficiency. Patients presenting with upper-extremity symptoms deserve imaging of the runoff vessels down to and including the digital arteries. Patients with TIA and/or stroke deserve imaging of the intracranial and the extracranial vessels as well as CT or MR of the brain.