Thoracic outlet syndrome (TOS) consists of a group of distinct disorders that affect the nerves in the brachial plexus (nerves that pass into the arms from the neck) and various nerves and blood vessels between the base of the neck and axilla (armpit). For the most part, these disorders have very little in common except the site of occurrence. The disorders are complex, somewhat confusing, and poorly defined, each with various signs and symptoms of the upper limb. True neurologic TOS is the only type with a clear definition that most scientists agree upon.The disorder is rare and is caused by congenital anomalies (unusual anatomic features present at birth). It generally occurs in middle-aged women and almost always on one side of the body. Symptoms include weakness and wasting of hand muscles, and numbness in the hand.

Treatment for individuals with TOS varies depending on the type. True neurologic TOS is generally effectively treated with surgery. Most other forms need only symptomatic treatment. Common or disputed TOS requires conservative treatment which may include drugs such as analgesics, and physical therapy to increase range of motion of the neck and shoulders, strengthen muscles, and induce better posture. Some cases of disputed TOS may require surgery (although, like the diagnosis, surgery is controversial). Heat, analgesics, and shoulder exercises have been used with limited success in individuals with traumatic TOS. Surgery may be needed in some cases. Vascular TOS often requires surgery.

The prognosis for individuals with TOS varies according to the type. For the majority of individuals who receive treatment the prognosis for recovery is good.

Prepared by the National Institutes of Health