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Thoracic outlet syndrome (TOS) is a syndrome involving compression at the thoracic inlet, which is known clinically as the superior thoracic outlet resulting from excess pressure placed on a neurovascular bundle passing between the anterior scalene and middle scalene muscles. 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, the subclavian vein. TOS may result from a ''positional'' cause, for example, by abnormal compression from the clavicle (collarbone) and shoulder girdle on arm movement. There are also several ''static'' forms, caused by abnormalities, enlargement, or spasm of the various muscles surrounding the arteries, veins, and/or brachial plexus, a fixation of a first rib, or a cervical 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. 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 etiologies, first rib fixations, scalene muscle spasm, and a cervical rib or fibrous band. ==Signs and symptoms== TOS affects mainly the upper limbs, with signs and symptoms manifesting in the arms and hands. Pain is almost always present and can be sharp, burning, or aching. It can involve only part of the hand (as in the 4th and 5th finger only), all of the hand, or the inner aspect of the forearm and upper arm. Pain can also be in the side of the neck, the pectoral area below the clavicle, the armpit/axillary area, and the upper back (i.e., the trapezius and rhomboid area). Decoloration of the hands, one hand colder than the other hand, weakness of the hand and arm muscles, and tingling are commonly present. TOS is often the underlying cause of refractory upper limb conditions like frozen shoulder and carpal tunnel syndrome that frequently defy standard treatment protocols. TOS can be related to Forward head posture. A painful, swollen and blue arm, particularly when occurring after strenuous physical activity, could be the first sign of a subclavian vein compression related with an unknown TOS and complicated by thrombosis, the so-called Paget–Schroetter syndrome or effort-induced thrombosis. TOS can be related to cerebrovascular arterial insufficiency when affecting the subclavian artery. It also can affect the vertebral artery, in which case it could produce vision disturbances, including transient blindness, and embolic cerebral infarction. TOS can also lead to eye problems and vision loss as a circumstance of vertebral artery compression. Although very rare, if compression of the brain stem is also involved in an individual presentation of TOS, transient blindness may occur while the head is held in certain positions.〔http://www.ncbi.nlm.nih.gov/pubmed/7931599〕 If left untreated, TOS can lead to neurological deficits as a result of the hypoperfusion and hypometabolism of certain areas of the brain and cerebellum. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「thoracic outlet syndrome」の詳細全文を読む スポンサード リンク
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