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Thoracic Outlet Syndrome


The thoracic outlet syndrome (TOS) consists of three separate compartments- the interscalene triangle, the costoclavicular space, and the retropectoralis minor space [1]. Thoracic outlet syndrome occurs secondary to compression of the neurovascular structures crossing the thoracic outlet [1]. It is caused by the impingement of the brachial plexus nerves, subclavian artery, and subclavian vein in the area just above the 1st rib and behind the clavicle [2].

Affected patients are generally 20-40 years in age and there is a female predominance (4:1) [1] although other authors indicate no sex predilection [3]. More than 90% of cases present with neurologic symptoms, whereas fewer than 10% of patients have vascular only or combined neurogenic and vascular symptoms [2]. The symptoms consist of pain, numbness, tingling, and weakness of the upper extremity that is exacerbated by activity requiring elevation or sustained use of the arm [1].The end stage of neurogenic TOS can result in Gilliatt-Sumner hand in which there is atrophy of the hand muscles, as well as hyperesthesia in the ulnar and medial antebrachial cutaneous distributions with normal median nerve sensation [3].

Venous TOS is the second most common form [3]. The typical site of subclavian vein compression is at the level of the costoclavicular space between the first rib, subclavius muscle, and clavicle [3]. Most patients present with spontaneous axillosubclavian thrombosis (Paget-von Schrotter syndrome), although symptoms of intermittent venous compression in the absence of thrombosis is also seen (McCleery syndrome) [3]. Arterial TOS is the rarest form accounting for less than 3% of cases and most affected patients are young and otherwise healthy and report a history of vigorous use of the arm in occupational or recreational activities [3]. Arterial TOS is almost always associated with an underlying bone abnormality (cervical rib or anomalous first rib) [3]. Arterial TOS classically presents with symptoms of distal ischemia including weakness, cold limb, and pain [3]. Patients with vascular symptoms warrant early recognition and treatment to avoid devastating complications such as pulmonary embolism, gangrene of the hand (associated with Paget-von Schrotter syndrome), digital ischemia, or stroke due to emboli originating in the subclavian artery [2]. Stent placement is not recommended as stent placement alone without surgical intervention generally fails and the presence of the stent can limit options for vein reconstruction after stent failure [3].

Antomic variations that can increase the risk for thoracic outlet syndrome include a cervical rib or an elongated transverse process of C7 [1]. Thin women with poor posture and weak muscle support also seem to be predisposed to TOS [1]. Most patients also have a history of trauma (such as a hyper-extension neck injury) or a work related repetitive movement [3].


Cervical ribs occur in up to 6% of individuals and are twice as common in women [3]. Cervical ribs are commonly incomplete (70% of cases) and usually have a thick ligament extending from their tip to the first rib [3]. Complete cervical ribs account for 30% of cases and attach to the normal first rib by fusion or by forming a joint [3]. Most patients with cervical ribs are asymptomatic, but an increased prevalence of cervical ribs has been noted in patients with TOS [3].

An elongated C7 transverse process is more common than a cervical rib (up to 25% of individuals) and is defined as extending laterally beyond the transverse process of T1 [3].

CT angiography can demonstrate vascular compression and the adjacent anatomic structures [1]. Imaging should be performed with the arms alongside the body and then with the arms elevated [1]. Contrast should be injected on the contralateral side [1]. Arterial compression is easily identified, however, venous compression is very difficult to discriminate as it is frequently seen in asymptomatic subjects when the arms are elevated (seen in over 50% of asymptomatic patients) [1,3]. Venous thrombosis, focal fixed subclavian vein stenosis, and collateral circulation are objective evidence for venous TOS [1].

On MR, findings suggestive of neurogenic TOS include edema in the brachial plexus or loss of the fat surrounding the brachial plexus with abduction [3].


(1) Radiographics 2006; Demondion X, et al. Imaging assessment of thoracic outlet syndrome. 26: 1735-1750

(2) AJR 2012; Ersoy H, et al. Vascular thoracic outlet syndrome: protocol design and diagnostic value of contrast-enhanced 3D MR angiography and equilibrium phase imaging on 1.5- and 3-T MRI scanners. 198: 1180-1187

(3) Radiographcis 2016; Raptis CA, et al. Imaging of the patient with thoracic outlet syndrome. 36: 984-1000

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