Clinical Features
In cases of suspected TOS, clinicians should take a thorough history and perform a thorough physical examination. The differential diagnosis for unilateral, upper limb pain, numbness, tingling, and/or weakness exacerbated by movement includes shoulder and rotator cuff pathology, cervical spine injury, cervical radiculitis, distal compressive neuropathies (carpal or cubital tunnel syndrome), and neuralgic amyotrophy (Parsonage-Turner syndrome/acute brachial radiculitis).27,28 The clinician should pursue a history of trauma to the shoulder or neck as well as any occupational or recreational activities involving elevation of the upper extremity for extended periods.29 Physical examination must include an evaluation of the contralateral side and may begin with visual inspection to assess for muscle asymmetry, atrophy, color changes, edema, or deformities.18 Next, palpation should be used to assess for any tenderness, texture changes, masses, or vascular pulsations. Attention should be directed at examination of the cervical spine as well as neurologic and vascular assessments of the bilateral upper extremities, including range of motion and strength testing,18 to rule out alternative etiologies.
Four basic maneuvers—the Roos test,30 Adson test,31 Wright test,32 and costoclavicular test—traditionally have been used to diagnose TOS. A positive Roos test involves symptom reproduction with the patient slowly opening and closing the hand for 3 minutes with the arm externally rotated and abducted to 90°.33 However, the false-positive rate of the Roos test is as high as 77% in patients with carpal tunnel syndrome and up to 47% in normal subjects.34 The Adson test is performed by having the patient inhale deeply while the arm is kept in the anatomical position with the head extended and turned toward the involved extremity. The examiner monitors the radial pulse; an absent or diminished radial pulse suggests compression of the subclavian artery. The Adson test is not very reliable, however, because the pulse diminishes even in normal subjects,6,26 with a reported false-positive rate of 13.5%.35 A positive costoclavicular compression test occurs when depressing a patient’s shoulder reproduces symptoms. In one study, the false-positive rate of the costoclavicular compression test was 48% in patients with carpal tunnel syndrome and 16% in normal subjects.34 Last, the Wright test is performed by hyperabducting and externally rotating the affected shoulder. It is positive with a diminished pulse or reproduction of symptoms. One study found that the Wright test had 70% to 90% sensitivity and 29% to 53% specificity.36
Clinically distinguishing between the various forms of TOS may be difficult, and occasionally multiple types exist in a single patient, exacerbating one another and adding to the diagnostic difficulty. For example, arterial insufficiency may lead to disruption of the neural microcirculation, leading to concurrent arterial and neurogenic TOS. Because most cases present with nonspecific symptoms, advanced imaging modalities are often required to establish a definitive diagnosis and to target therapy to the appropriate site of compression.
Imaging Features
Plain Radiography
First, cervical spine and chest radiographs should be obtained to assess for bone abnormalities, including cervical ribs, long transverse processes, rib/clavicle fracture callus, rib anomalies, degenerative spine disease, and neoplasm (Pancoast/apical tumor) (Figure 1).18,25
Ultrasonography
Ultrasonography is useful in evaluating arterial or venous TOS because of its low cost, noninvasive nature, and high specificity for vessel occlusion.37,38 In arterial TOS, ultrasound may demonstrate increased flow velocity through a stenosis or an aneurysmal degeneration distal to the stenosis.7 In venous TOS, duplex ultrasound can identify stasis and thrombus.7 Obtaining duplex ultrasound with the upper extremity in multiple positions allows clinicians to correlate dynamically induced symptoms with ultrasonographic findings of altered blood flow.39-41 Despite the purported benefits of ultrasound, its drawback is that it is operator-dependent,42 with some studies reporting a high false-positive rate24 for diagnosis of venous TOS.
Electrodiagnostic Testing
Ruling out etiologies such as cervical radiculitis (Parsonage-Turner syndrome), cervical radiculopathies, brachial plexus lesions, and other distal compressive neuropathies requires nerve conduction studies and electromyography.18,43-46 In true neurogenic TOS, a combination of decreased sensory nerve action potentials in the ulnar and medial antebrachial cutaneous nerves and decreased compound motor action potentials in the median nerve is often found.18 Specifically, an abnormal ulnar sensory nerve action potential suggests the lesion is situated away from the intraspinal canal, which argues against a diagnosis of radiculopathy or myelopathy.43,44 In the disputed form of neurogenic TOS, the role of electrodiagnostic testing is less clear.18
Conventional Arteriography and Venography
Although CTA has superseded conventional arteriography and venography in most treatment centers, it may still be used in patients with acute symptoms requiring immediate thrombolytic therapy. Catheter angiography and venography with postural maneuvers are often the first invasive treatment modality in cases of thoracic outlet vascular compression.22,24 Presence of intraluminal thrombus, vessel dilatation, and collateral vessels is readily demonstrated (Figure 2A). Recanalization of occluded vessels can be attempted using balloon angioplasty and venoplasty (Figure 2B), but it is usually only temporarily successful if the cause of extrinsic compression is not corrected (Figures 2C, 2D). CTA or conventional angiography, used if sophisticated CTA with 3-dimensional (3-D) reconstruction is unavailable, is the gold standard in diagnosis of TOS.
