Several clinical maneuvers and tests are used in patients with thoracic outlet syndrome, including Adson’s maneuver, the Wright test, and the Halsted maneuver. Positive test results are due to compression of the arterial system, rather than to compression of the brachial plexus. Sensitivity and specificity of these tests for compression of the brachial plexus is limited (67-69).
Roos’ test reproduces the patient’s symptoms when the patient’s arms are maintained in a position of neural tension and/or compression. The sensitivity and specificity of this test is not verified to date, and the test does not isolate or demonstrate a specific point of nerve compression.
Electromyography and nerve conduction velocity (EMG/NCV) studies have limited utility in the diagnosis of thoracic outlet syndrome. These examinations are limited by the difficulties in placing electrodes over the proximal components of the brachial plexus, by the inability to measure the length of these proximal components to determine velocity, by the small area of nerve damage relative to the length of the nerve, and by the pathophysiology of chronic nerve compression. In chronic nerve compression, smaller sensory nerves are affected earlier and to a greater extent than are the larger motor nerves, and there is a long continuum of progressive nerve damage, from segmental demyelination to complete demyelination to Wallerian degeneration of the axons. There is controversy regarding the point in this continuum at which EMG/NCV will detect an abnormality. Interestingly, there is a small amount of evidence demonstrating abnormal function of the proximal brachial plexus at surgery (38), but these areas are inaccessible to routine clinical EMG/NCV. When EMG/NCV abnormalities are present in patients with TOS, advanced nerve damage is present (due to fibrous bands in the thoracic outlet), with motor abnormalities that are very unlikely to resolve after surgery (38, 70). Therefore, EMG/NCV is used primarily to rule out other peripheral neuropathies, rather than to rule in TOS.
Cervical spine radiographs are frequently utilized in the evaluation of patients with thoracic outlet syndrome, as early descriptions of the syndrome invariably involved patients with cervical ribs. However, as knowledge of TOS progressed, it became apparent that the vast majority of cases of neurogenic TOS are associated with soft tissue abnormalities, without cervical ribs. Currently, cervical spine radiographs have a limited role in the evaluation of these patients. If cervical ribs are present in a patient with the typical presentation of TOS, the diagnosis is easily made. Most of these patients have the arterial form of TOS. If cervical ribs are not present in a patient with the typical presentation of TOS, the diagnosis is vastly more challenging.