Thoracic Outlet Syndrome

The thoracic outlet is the region along the pathway of the brachial plexus from just distal to the nerve roots exiting the intervertebral foramen to the lower border of the axilla.. The outlet is bordered medially by the scalenus anterior, medius, and posterior and the first rib; posteriorly by the upper trapezius and scapula; anteriorly by the clavicle, coracoid, pectoralis minor, and deltopectoral fascia; and laterally by the axilla. The plexus enters the outlet between the scalenus anterior and medius; the subclavian artery runs posterior to the scalenus anterior; and the subclavian vein runs anterior to the scalenus anterior. The blood vessels join the brachial plexus and course together under the clavicle, over the first rib, and under the coracoid process posterior to the pectoralis minor. Vascular and/or upper extremity neurological symptoms that are not consistent with nerve root or peripheral nerve dermatome and myotome patterns should lead the therapist to suspect thoracic outlet problems.

Related Diagnoses

Thoracic outlet syndrome (TOS) encompasses a variety of clinical problems in the shoulder girdle region. The diagnosis itself is controversial because of the clinical complexity and variability in presentation that involve upper extremity neurological and vascular symptoms, including pain, paresthesia, numbness, weakness, discoloration, swelling, loss of pulse, ulceration, gangrene, and in some cases Raynaud’s phenomenon. Patients also complain of headaches, which may be related to posture, tension, or vascular compromise. Diagnoses that have been used to describe TOS include cervical rib, scalenus anticus syndrome, costoclavicular syndrome, subcoracoid-pectoralis minor syndrome, droopy shoulder syndrome, and hyperabduction syndrome. Commonly accepted medical diagnoses include:
• Neurogenic TOS-true TOS. This condition is rare. The patient presents with some anatomical abnormality such as cervical rib or elongated C7 transverse process. The patient describes paresthesias and pain along the medial border of the arm and experiences muscle weakness; there is atrophy in the intrinsic muscles of the hand. There are also positive electromyographic (EMG) findings. The condition is often misdiagnosed as carpal tunnel syndrome.

• Nonspecific “symptomatic” neurogenic TOS. This condition is similar to true TOS, but there are no anatomical abnormalities detected by radiography, no muscle atrophy, and no EMG findings. Often there is a postural component. Most TOS complaints fall into this category.

• Vascular syndromes-arterial. In some cases there is a small incidence of arterial compression. This condition is rare and is usually the result of structural abnormalities such as cervical rib. There is compression of the artery with arm motion, especially overhead usage. If the arm fatigues with overhead usage, the person may have to adapt work habits that avoid risk from repetitive trauma to the artery.

• Vascular syndromes-venous. Compression of the subclavian vein does not typically occur in TOS; venous symptoms would be from some other cause, such as thrombosis. Acute thrombosis (sudden, painful swelling with bluish discoloration of the arm) is usually dealt with medically, but the therapist should always be suspicious of unexplained swelling of the arm. Effort thrombosis could occur from sudden maximal arm use, or there could be insidious onset of swelling with prolonged use. If these occur, the patient’s physician should be contacted.

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