Thoracic Outlet

What is the thoracic outlet?

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The thoracic outlet refers to the area circumscribed by the first rib, the sternum and the first thoracic vertebra. The volume of this space is dynamic, meaning it changes as you breathe in and out and with any movement of the arm, neck or thorax. The brachial plexus is a nerve trunk extending from the lower four cervical nerves and through the first thoracic nerve and serves the upper and lower arm as well as the hand.

Thoracic Outlet Syndrome occurs when either the brachial plexus or the blood vessels is impinged upon by bony structures. This may cause pain and/or functional deficit. There are three types of TOS, namely neurogenic, atrial and venous. Of these, neurogenic TOS is responsible for 95 percent of all cases.

Causes of Thoracic Outlet Syndrome

What factors can cause bony structures to impinge upon the brachial plexus? Some cases are congenital, resulting from the existence of an extra rib located above the first “normal” rib. This spare rib can crush the nerves and blood vessels. Many cases are caused by trauma. It is possible for someone to be born with an extra rib and not even notice it until they experience an injury from a fall or motor vehicle accident.

Work activities involving carrying shoulder loads for long periods, pulling shoulders back and down or reaching above shoulder level can trigger an episode of TOS. A violent injury may tear the shoulder muscles, leading to a build-up of scar tissue that impinges upon the nerves and blood vessels.

Treatment of Thoracic Outlet Syndrome

In many cases, TOS will resolve on its own without treatment. If your case of TOS involves an extra rib, your surgeon may decide to remove it in order to relieve your symptoms. Drug treatment may involve painkillers, non-steroidal anti-inflammatories, thrombolytics and/or anticoagulants. Your doctor may also refer you for physiotherapy or occupational therapy.