Diagnosis edit
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[1] and Dr. Herbert I. Machleder published the "Diagnosis of Thoracic Outlet Syndrome Using Electrophysiologically Guided Anterior Scalene Blocks"[2] 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.) [3] This method of guidance for selective muscle blocks is rarely used today, for two major reasons. First, the accuracy of placement of the needle tip with EMG is controversial; ultrasound, CT or MRI are likely much more accurate. Second, there is no control over the spread of injectate. Any medication or other injectate could leak out of a confined structure such as a muscle and flow to adjoining structures, such as the brachial plexus. Should this occur, direct anesthesia of the brachial plexus could result in decreased symptoms, but without any clinical significance regarding the role of the muscle into which the injection was attempted. Making a judgement about correlation with surgical success is, thus, somewhat perilous. There are a number of publications from the same center as the paper quoted above, and from other centers, regarding selective muscle injections using Botox or other agents in which the subjects had various adverse outcomes, such as long-term paralysis of a vocal cord, that prove the limited control over where injectate flows. For these reasons and others, the quoted paper does not support this method as a "gold standard" for the diagnosis of TOS.
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.[4]
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.[5] It should be noted that Doppler arteriography does not utilize probes at the fingertips and arms, and in this case is likely being confused with plethysmography, which is a different method that utilizes ultrasound without direct visualization of the affected vessels. It should also be noted that Doppler ultrasound (not really 'arteriography') would not be used at the radial artery in order to make the diagnosis of TOS. Finally, even if a Doppler study of the appropriate artery were to be positive, it would not diagnose neurogenic TOS, by far the most common subtype of TOS. There is plenty of evidence in the medical literature to show that arterial compression does not equate to brachial plexus compression, although they may occur together, in varying degrees. Additionally, arterial compression by itself does not make the diagnosis of arterial TOS (the rarest form of TOS). Lesser degrees of arterial compression have been shown in normal individuals in various arm positions, and is thought to be of little significance without the other criteria for arterial TOS.
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). [citation needed].
High resolution MRI/MRA of the Brachial Plexus[citation needed].