Arterial Thoracic Outlet Syndrome (TOS)
Affects 2-5% of all patients with TOS.
Arterial TOS is caused by subclavian artery compression within the scalene triangle leading to the development of occlusions or aneurysms. These lesions almost always occur in association with a congenital cervical rib or other bony anomaly.
Ulcerative subclavian artery lesions and aneurysms are often accompanied by mural thrombus formation (a type of blood clot) and are frequently complicated by distal thromboembolism with hand and/or digital ischemia.
Subclavian artery occlusions or aneurysms may be asymptomatic, with occlusions identified by a significant blood pressure differential between arms and aneurysms occasionally presenting as a non-tender mass in the lateral neck.
Patients with arterial TOS may have one or more of the following symptoms:
- A sudden onset of hand pain and weakness
- Numbness and tingling in the hand or fingers
- Cold and pale fingers
- Chronic arm fatigue with use or claudication
- Non-healing wounds or ulcerations in the fingers
The diagnosis is suspected by clinical findings and confirmed by imaging studies, such as Duplex ultrasound imaging and vascular laboratory studies, contrast-enhanced CT or MR angiography, or traditional catheter-based arteriography.
Immediate anticoagulation and urgent surgical treatment is undisputed in patients with acute upper extremity ischemia and may initially involve surgical removal of the blood clot(s), or thromboembolectomy, to improve the distal circulation in the hand.
In all symptomatic patients, definitive surgical treatment also requires thoracic outlet decompression with removal of the cervical and first ribs, and resection and graft reconstruction of the subclavian artery.
In asymptomatic patients, thoracic outlet decompression without arterial reconstruction may be sufficient, accompanied by follow-up imaging studies to monitor any long-term changes in the artery.
Unresolved questions regarding arterial TOS include:
- Best methods to achieve early diagnosis
- Indications for surgical treatment of small subclavian aneurysms
- The role and timing of surgical treatment in patients with cervical ribs and mild-moderate arterial stenosis
- Exact surgical techniques by which to obtain optimal long-term results
- The role of adjunctive therapies for digital vasospasm, post-ischemic neuropathy, and reflex sympathetic dystrophy (complex regional pain syndrome) that may accompany this condition
A second form of arterial TOS is observed almost solely in overhead throwing athletes (e.g., baseball pitchers), which results in occlusive or aneurysmal lesions of the distal axillary artery near the shoulder. These lesions are thought to be caused by repetitive trauma to the vessel during the hyperextension of the arm associated with the throwing motion. During this activity, the axillary artery can be repetitively compressed in its relatively fixed position by forward motion of the head of the humerus. In time, this type of repetitive injury can lead to either reactive thickening of the artery wall (intimal hyperplasia) with surface ulceration, or to aneurysm formation.
The complications of these lesions are similar to those of arterial TOS caused by subclavian artery lesions at the level of the first rib. Immediate anticoagulation and prompt surgical intervention is warranted. The surgery entails a direct axillary artery graft reconstruction (and distal thromboembolectomy when necessary) and is usually effective in restoring arterial flow to the hand. Most patients can expect to successfully return to previous levels of activity.