Thoracic outlet syndrome can be subdivided into neurogenic, venous, and arterial types depending on which structures are compressed in the interscalene triangle or costoclavicular space.

Neurogenic thoracic outlet syndrome is the most common (over 90% of patients) and often the most difficult to diagnose and treat effectively. Patients most often present with supraclavicular and anterior chest wall burning pain and with segmental pain and paresthesias of the arm in an ulnar nerve distribution. Weakness of the intrinsic muscles of the hand is not uncommon. Thenar or hypothenar muscle wasting is rare. There is usually a history of whiplash trauma (motor vehicle accident, fall, assault) or repetitive activity of the upper extremity (word processing, filing), particularly overhead activities (lifting). Physical examination will often disclose supraclavicular tenderness and positive brachial plexus tension testing. A positive Adson test (obliteration of the radial pulse on inspiration while turning the head away from the affected side), or a positive Roos test (reproduction of symptoms with rapid opening and closing of the hand with the arm 90 degrees abducted at the shoulder and 90 degrees flexed at the elbow), or a positive Tinel sign (tingling in the distribution of the nerve produced by tapping in the supraclavicular interscalene region) may also be elicited.

Presence of a cervical rib or other bony anomalies should be excluded by chestradiograph. Electrophysiologic testing is usually negative. The cornerstone of treatment is specific physical therapy treatment such as the Edgelow Neurovascular Entrapment Self-Treatment (ENVEST) program, beginning with breathing exercises and attention to posture. Transcutaneous electrical nerve stimulation (TENS) can be helpful. Surgery is indicated in severe refractory cases and involves resection of the hypertrophied anterior and middle scalene muscles, brachial plexus neurolysis, and resection of bony abnormalities. Although in carefully selected patients the initial surgical outcome is excellent, symptoms return within a year in as many as 25%, presumably due to late postoperative scarring around the nerve roots.

Venous thoracic outlet syndrome involves external compression of the subclavian vein by the first rib, anterior scalene muscle, clavicle, and costocoracoid ligament. A history of repetitive upper arm exercises or clavicular fracture is common. Positional venography is essential in the diagnosis of venous thoracic outlet syndrome; external compression of the vein and filling of venous collaterals are demonstrated by abduction of the arm. Thrombosis of the involved vein segment is known as Paget-Schroetter syndrome, or effort thrombosis, and often presents as acute unilateral arm edema, axillary fullness, hand cyanosis, and enlarged shoulder and chest wall collateral veins in an otherwise healthy patient. Evaluation for hypercoagulable state, including plasma levels of antithrombin III, factor V Leiden, cardiolipin antibody, and proteins C and S, is recommended, as an abnormality is detected in 56% of patients presenting with acute axillary-subclavian vein thrombosis. Treatment for symptomatic venous thoracic outlet syndrome involves anterior and middle scalenectomy and first rib resection with venolysis, which can be performed through a supraclavicular, a combined supra- and infraclavicular, or a transaxillary approach. If the vein is thrombosed, multimodality therapy is employed: preoperative thrombolysis followed immediately by surgery with intraoperative angioplasty of any residual venous stenosis. If the vein cannot be recannulated preoperatively, surgical thrombectomy may be required. The prognosis is excellent with appropriate treatment.

Arterial thoracic outlet syndrome is the least common of these disorders and involves compression of the subclavian artery between the anterior and middle scalene muscles. It most often produces subclavian artery stenosis and poststenotic dilation, which result in digital ischemia due to atheroemboli. These lesions can be subtle, often requiring magnified multiplanar views to be shown angiographically. Arm claudication is a less common presentation. The Wylie-Allen test (performed by exsanguinating the arm with elevation, occluding the radial and ulnar arteries at the wrist, and observing capillary refill of the hand when these arteries are released) may reveal occult digital artery occlusions that can be confirmed by angiography. Treatment involves removal of the anterior and middle scalene muscles, first rib resection, and resection of the affected subclavian artery with replacement by a polytetrafluoroethylene interposition graft.

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