Thoracic outlet syndrome is a condition where the neurovascular (nerves, blood) structures that service the arm get compressed outside of the spine (a peripheral neuropathy). The compression can come the collarbone, the scalene muscles at the base of the neck, an apical tumor or other mass. Thoracic outlet syndrome can be unilateral (one side) or bilateral (both sides).
The brachial plexus is a bundle of nerves that eventually form the major nerves of the arm: median, radial, and ulnar. It passes directly underneath the center of the collarbone. The subclavian artery, which becomes the brachial artery, is right next to it and supplies blood to the arm. The collarbone (clavicle) connects your shoulder blade (scapula) to your breastbone (sternum). There is only a few millimeters clearance between the bottom of the collarbone and the ribcage, so proper alignment of these structures is absolutely critical for the nerves and blood vessels to work unobstructed.
Trauma to the shoulder complex, repetitive shoulder movements (like a baseball pitch), a long history of sleeping on your side, and a habit of carrying a heavy bag with a strap over your shoulder, or a history of carrying any other heavy objects on the shoulder such as a 5-gallon water bottle are some of the things that can cause the collarbone to close down on the neurovascular bundle. Symptoms can include numbness down the arm; hand numbness, arm and hand weakness, pins and needles sensation in the fingertips, and poor circulation in the arms (feeling of swelling or fullness).
A cervical rib can predispose one to thoracic outlet syndrome. A cervical rib is a congenital anomaly where a small rib branches from the lower neck vertebrae. A cervical rib can easily obstruct the brachial plexus on that side.
A syringomyelia or syrinx is a slowly expanding fluid filled sac in the spinal cord, usually at the neck level, that places dangerous pressure to the cord; enough to cause muscle atrophy (wasting) of the areas served by the affected neurons. Although syringomyelias are rare, they must be ruled out first.
If you are experiencing upper extremity numbness, see your doctor. You should get referred to an orthopedic specialist who can do some tests to properly diagnose your condition. If thoracic outlet syndrome is suspected, your doctor may order a nerve conduction or needle electromyograph (EMG) study to determine if the nerve is compromised. Typically, physical therapy is prescribed for several weeks. If there is no improvement, surgery may be recommended.
The exercise below can be helpful for some sufferers of thoracic outlet syndrome, especially the type that involves the collarbone pressing down on the neurovascular bundle. It is simple to do, and generally safe. This exercise attempts to lift the collarbone repeatedly off the ribcage, creating more space for the brachial plexus and subclavian artery. Do at least 100 per day for a week; if relief is felt, continue doing as needed. If at any point your symptoms feel worse, stop immediately.