Thoracic Outlet Syndrome (TOS) is a generalized term to describe a set of clinical problems which are caused by constriction of the blood vessels or nerves in the thoracic outlet. The thoracic outlet is an area in the body that borders the upper arm, the base of the neck, above and behind the clavicle, and the first rib (figure 1). It is like a tunnel for the nerves and blood vessels that supply your arm to travel through. While bony and muscular abnormalities (cervical ribs) certainly can cause symptoms, most often they are absent. A lot of times pre-existing trauma or repetitive motions are a major contributor.
There are three types of TOS: neurogenic, venous and arterial.
Neurogenic TOS (NTOS) is the most frequent form of TOS, with 90 percent of patients being neurogenic. Symptoms include upper extremity pain, tingling and numbness, particularly when asked to perform certain physical exam maneuvers such as elevating the arm or extending the neck. The symptoms of NTOS can be attributed to compression of the brachial plexus (nerves supplying arm) at the scalene triangle (base of neck) and/or sub-coracoid space (by the shoulder). Often, response to muscle blocks is used as a diagnostic tool and helps determine surgical response for those suffering with NTOS. Occasionally, patients have isolated symptoms that may be attributed to compression of the arm nerves by the chest muscle (pectoralis minor syndrome). Due to the difficulty of diagnosis, patients are often misdiagnosed and often see multiple specialists while undergoing many diagnostic tests. While the majority of patients are best served by TOS-specific physical therapy, patients with unrelenting and disabling symptoms may require surgical treatment. Surgery for NTOS includes an incision in the neck from which the muscle (anterior scalene), bone (first rib and other bony anomalies) and scar tissue from nerves (brachial plexus neurolysis) is removed.
Venous TOS (VTOS) is caused by the compression of the major veins of the arm (axillary and subclavian). This can lead to acute swelling of the arm and blood clot formation (effort thrombosis). This condition often affects athletes and active individuals who do frequent upper extremity exercises. VTOS requires urgent diagnosis and treatment. Treatment is often staged. The first stage of treatment includes trying to dissolve the clot and the second stage is geared towards removing the anatomical compression (first rib resection, removal of anterior scalene) of the vein with possible vascular reconstruction.
Arterial TOS (ATOS), the rarest form of TOS, is caused by compression of the major arteries of the arm (axillary and subclavian). This can lead to acute ischemia of the arm, leading to tissue loss (ulcers and gangrene) and nerve damage. Additionally, ATOS may lead to formation of an aneurysm (bulge in the blood vessel) causing small blood clots (thrombus) to shower (embolize) to distal hand arteries.
TOS is a rare medical problem despite its presentation. While the vascular forms are more straightforward to diagnosis, they require prompt medical attention and treatment to prevent further complications. The diagnosis of TOS remains very difficult to figure out and often requires a team approach to formalize a diagnosis and design a treatment plan.