Thoracic outlet syndrome: A neurological and vascular disorder.
The term Thoracic Outlet Syndrome (TOS) comprises a set of symptoms due to compression, either neurogenic (nTOS, almost 95% of the cases) or vascular (vTOS) in nature. To date, adequately diagnosing TOS remains difficult because the lack of a gold standard and a wide spectrum of anatomic variations, also present in the asymptomatic population.
Normally, the brachial plexus is situated next to the lateral border of the anterior scalene muscle (ASM), passing underneath the clavicle and over the first rib and eventually running under the pectoralis minor muscle. The left and right subclavian arteries go up into the neck before bending laterally towards the medial margin of the ASM – they run behind this muscle and subsequently descend along with the brachialis plexus towards the arm.
Causative mechanisms include among others the presence of a cervical rib and postural abnormalities. Compression of the neurovascular bundle is generally thought to occur at three sites, that is: 1) the interscalene triangle; 2) the costoclavicular space ; and 3) the pectoralis minor/ subcoracoid space.
Four tests are available to clinically establish the specific diagnosis of TOS: the Adson/ scalene test, the Halstead Maneuver, the Wright hyperabduction maneuver and the Roos test. A positive result on a single test is not reliable. Conservative management through physiotherapy should be aimed at reducing the strain on the neurovascular bundle via postural adjustments. > From: Klaassen et al., Clin Anat (2013) (Epub ahead of print). All rights reserved to Wiley Periodicals, Inc.
The Pubmed summary of the article can be found here.