DIAGNOSIS OF TOS
How is TOS diagnosis made?
Careful history and physical examination are essential keys to suspect thoracic outlet syndrome. Throughout examination with provocative tests is essential part of patient evaluation. Clinical examination may reveal pain and tenderness in the supraclavicular area. Neurological examination of the arm and hand is of paramount importance and may demonstrate hypesthesia (numbness) as well as muscle paresis (weakness) and even atrophy (wasting). The presence of muscle weakness is particularly important since it is an indicator of disease severity.
Provocative testing is essential part of clinical examination. The purpose of these tests is to elicit TOS symptoms using specific clinical maneuvers in order to establish diagnosis. Elevated arm stress test (EAST or Roos test), upper limb tension tests (ULTT’s) and Adson tests are most commonly used.
Radiographic examination plays an important role in diagnosing TOS. X-ray, CT scan, MRI, Doppler USG are commonly used radiological tools.
X-ray is a very good tool to visualize bone structures. If an accessory cervical rib is present it is visible on plain X-ray. It is also helpful to differentiate advanced cervical degenerative disc disease from TOS.
CT scan is also an excellent tool to visualize bone as well as soft tissue. CT angiography (CTA) is a superb tool to demonstrate subclavian vessels in a non-invasive way. 3 dimensional CT and/or CTA reconstructions can be particularly helpful for preoperative assessment.
Doppler ultrasonography or Duplex scan is a non-invasive method to evaluate blood flow in the vessels. It is particularly useful in vascular TOS cases. It can demonstrate the presence of subclavian vein thrombosis. High resolution USG of brachial plexus is relatively new method to visualize brachial plexus and can directly demonstrate the site of compression.
MRI is the most effective tool to demonstrate soft tissue. It can differentiate TOS from cervical disc disease. MRI neurography visualizes brachial plexus itself with high accuracy. Diffusion tensor imaging (DTI) can demonstrate nerve fiber orientation in the brachial plexus and show potential compression sites.
Above, there is 3-dimensional CT angiographic reconstruction from a patient with TOS. Note that subclavian artery narrows as it passes over accessory rib. The accessory rib makes an abnormal joint with the first rib (white circle).
Nerve conduction studies like EMG and ENG may be helpful, but in the majority of cases do not provide definitive diagnosis. Thus, the diagnosis is mainly made by careful clinical examination.