Thoracic Outlet Syndrome

Peter Abaci, MD Los Gatos, California

Patients routinely present to occupational health clinics with complaints of upper-extremity pain, numbness, and weakness. While there are a number of well-established conditions and diagnoses that can present with these symptoms, thoracic outlet syndrome (TOS) is a less common and sometimes controversial diagnosis that also gets considered. But what is thoracic outlet syndrome, and where does it fit in the diagnosis and treatment of upper-extremity injuries?

Thoracic outlet syndrome comprises a varied and diffuse set of disorders that cause compression of what is termed the neurovascular bundle, comprising the brachial plexus, subclavian vein, and subclavian artery, as it exits through the thoracic outlet. The thoracic outlet is the area at the base of the neck between the clavicle and the first rib. It is marked off by the anterior scalene muscle in the front, the middle scalene muscle in the back, and inferiorly by the first rib. The brachial plexus is a network of nerves that carry input from the spinal cord to the arm and hands and that intertwine like the Los Angeles freeway system. Compression of any three of these components can lead to a diagnosis of TOS, but over 90 percent of the cases involve the nerves of the brachial plexus.

Causes