Thoracic outlet syndrome

Thoracic outlet syndrome (TOS) is a syndrome involving compression at the superior thoracic outlet[1] resulting from excess pressure placed on a neurovascular bundle passing between the anterior scalene and middle scalenemuscles.[2] It can affect one or more of the nerves that innervate the upper limb and/or blood vessels as they pass between the chest and upper extremity, specifically in the brachial plexus, the subclavian artery, and, rarely, thesubclavian vein.

TOS may result from a positional cause, for example, by abnormal compression from the clavicle (collarbone) andshoulder girdle on arm movement. There are also several static forms, caused by abnormalities, enlargement, or spasm of the various muscles surrounding the arteriesveins, and/or brachial plexus, a fixation of a first rib, or acervical rib. A Pancoast tumor (a rare form of lung cancer in the apex of the lung) can lead to thoracic outlet syndrome in the progressive stages of the disease. The most common causes of thoracic outlet syndrome include physical trauma from a car accident, repetitive strain injury from a job such as frequent nonergonomic use of a keyboard, sports-related activities, and anatomical defects such as having an extra rib. In pregnancy, if a narrow superior thoracic outlet exists previously, the patient can have symptoms for the first time. Joints loosen during pregnancy, making it easier to develop bad posture.[3]

Common orthopaedic tests used are the Adson's test, the Costoclavicular Manoeuvre, and the "Hands-Up" test or "EAST" test. Careful examination and X-ray are required to differentially diagnose between the positional and static aetiologies, first rib fixations, scalene muscle spasm, and a cervical rib or fibrous band.

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