Thoracic outlet syndrome.

Thoracic outlet syndrome (TOS) is an often misdiagnosed cause of neck, shoulder, and arm disability. Neurovascular compression may be seen in the interscalene triangle, costoclavicular space, or posterior to the pectoralis minor, although any cause of abnormalities of shoulder girdle alignment may cause a localized area of brachial plexus compression. Nerve compression in this way may lead to upper extremity weakness, pain, paresthesias, and numbness. A careful and detailed medical history and physical examination are essential to proper identification of thoracic outlet syndrome, which remains primarily a clinical diagnosis. Diagnostic testing may differentiate other causes of pain or neurologic symptoms of the upper extremity from TOS. Clinical management is often challenging.