Thoracic Outlet Syndrome - Diagnosis

Diagnosis

Adson's sign and the Costoclavicular maneuver lack specificity and sensitivity, and should comprise only a small part of the mandatory comprehensive history and physical examination undertaken with a patient suspected of having TOS. There is currently no single clinical sign that makes the diagnosis of TOS with any degree of certainty.

However, while there is no "gold standard" to diagnosis TOS Dr. Sheldon E. Jordan and Dr. Herbert I. Machleder published the "Diagnosis of Thoracic Outlet Syndrome Using Electrophysiologically Guided Anterior Scalene Blocks" in 1998. Previously anesthetic blocks of the anterior scalene muscle (AMS) had been used as a means of predicting which patients may benefit from surgical decompression. However the standard technique of using surface landmarks often resulted in inadvertent somatic block and sympathetic block because there is no reliable verification of needle tip localization. Their study was undertaken to determine if needle tip localization could be improved by using electrophysiological guidance. They determined that electrophysiological guidance facilitated accurate needle tip placement in the performance of ASM blocks; the result of these blocks appear to correlate with surgical outcomes. (Ann Vasc Surg 1998;12:260-246.)

Additional maneuvers that may be abnormal in TOS include the "stick em up hand raise" for up to 3–5 minutes, which involves holding both hands at right angles over the head bent at the elbows, with or without opening and closing of the fingers (a positive test occurs when the affected hand quickly becomes paler than the unaffected because of compromised blood supply), and the "compression test", when exerting pressure between the clavicle and medial humeral head causes radiation of pain and/or numbness into the affected arm.

Doppler Arteriography, with probes at the fingertips and arms, tests the force and "smoothness" of the arterial flow through the radial arteries, with and without having the patient perform various arm maneuvers (which causes compression of the subclavian artery at the thoracic outlet). The movements can elicit symptoms of pain and numbness and produce graphs with diminished arterial blood flow to the fingertips, providing strong evidence of impingement of the subclavian artery at the thoracic outlet.

Some physicians advocate the injection of a short-acting anesthetic such as xylocaine or marcaine into the anterior scalene, subclavius, or pectoralis minor muscles as a provocative test to assist in the diagnosis of thoracic outlet syndrome. This is referred to as a 'scalene block' when employing the use of a local anesthetic. This is not considered a "treatment", however, as the relief is expected to wear off within an hour or two at most. Active clinical research continues into the specificity, sensitivity, risks and benefits of this provocative test and other types of neuromuscular blocks, particularly at Johns Hopkins Hospital in Baltimore, Maryland (US)..

High resolution MRI/MRA of the Brachial Plexus.