Thoracic Outlet Syndrome (TOS)
What is thoracic outlet syndrome?
Your thoracic outlet is a small space just behind and below your collarbone. The blood vessels and nerves that serve your arm are located in this space. Thoracic outlet syndrome (TOS) is the presence of hand and arm symptoms due to pressure against the nerves or blood vessels in the thoracic outlet area. There are three types of TOS. The type depends on which structure is compressed -- nerve, vein, or artery. Ninety-five percent of cases of TOS are due to compression of the nerves to the arm (called neurogenic TOS). Three to 4 percent are due to obstruction or clotting of the main vein to the arm, the subclavian vein, a condition called venous TOS. The third type, arterial TOS, is the rarest type, occurring in 1 percent of cases, and it is due to disease in the artery leading to the arm, the subclavian artery. Almost all cases of arterial TOS are associated with an extra rib (cervical rib) or an abnormal first rib.
What are the symptoms?
The common symptoms depend on which structure is being compressed. In neurogenic TOS, the symptoms are pain, numbness, tingling, and/or weakness in the arm and hand. Also common is a tired feeling in your arm, which is made worse by working with your arms raised over your head. Neck pain and headaches in the back of your head are also frequent symptoms. Another common occurrence is pain that starts in your shoulder and runs down your arm, as well as pain in your fingertips. Unfortunately, the symptoms of neurogenic TOS can be vague and non-specific. Venous TOS is distinguished by swelling in your entire arm, plus pain and dark discoloration. Arterial TOS presents with pain, coldness, and a pale discoloration of the hand. Cramps occur when using the arm for activity.
What causes thoracic outlet syndrome?
Neurogenic TOS is most often the result of neck trauma such as a whiplash injury. Slipping and falling on floors or ice, or repetitive stress from working on assembly lines or keyboards are the next most common causes. The symptoms are due to scar tissue formation in neck muscles (called scalene muscles).
Venous TOS is commonly due to strenuous use of the arm and shoulder. Its underlying cause is congenital narrowing of the space through which the major arm vein (subclavian vein) passes from the shoulder area into the heart.
Arterial TOS is caused by a narrowing in the main artery to the arm (subclavian artery) which invariably is secondary to a congenital extra rib (cervical rib) which lies at the base of the neck, just above the highest rib in your chest, or it can be secondary to an abnormal first rib. Once the artery has been narrowed, one of two things will happen. The artery may enlarge, forming an aneurysm just beyond the narrowing, and a clot will form in the wall of the aneurysm; or the artery may remain narrowed and a clot will form inside the artery just beyond the narrowing. The danger of the clot is that pieces of it will break off (called emboli) and travel down the arm to block the circulation to your hand. When this occurs, the hand becomes cold, numb, painful, and discolored and you are in danger of losing your hand completely. Treatment to restore circulation is essential.
What tests will I need?
Diagnosing TOS can be complex. It begins by your physician asking you a series of questions to find out your symptoms and how the symptoms began. Depending on your symptoms, your doctor will be able to tell if you might have a nerve, vein, or artery problem which will then lead to an appropriate physical examination.
For neurogenic TOS, your physician will have you perform a number of provocative maneuvers. These consist of putting your neck and arms in different positions of stress to try to reproduce your symptoms. Other physical findings include tenderness in certain places in your neck, chest, or arms.
For venous TOS, physical examination consists primarily of noting swelling in your arm and prominent veins seen just under the skin at the spot where your shoulder joins your chest. In arterial TOS, physical exam often finds the pulse at your wrist is diminished or absent. Your hand may have a pale color compared to your pink, good hand.
To help determine whether or not you have TOS, your physician may order one or more of the following tests:
- Pulse volume recordings
- Computed tomography (CT) scan
- X-rays of the neck or shoulder
- Magnetic resonance imaging (MRI)
- Doppler ultrasound
- Nerve conduction velocity test
How is thoracic outlet syndrome treated?
Your particular treatment will depend on the type of TOS you have, as determined by your symptoms, physical examination and test results.
Neurogenic TOS is initially treated with physical therapy. The basic therapy methods include stretching exercises of your neck, posture correction, learning to avoid specific movements that bring on or aggravate your symptoms, and modifying your work site when appropriate. While some therapists may suggest strengthening exercises, most patients with neurogenic TOS are made worse by strengthening exercises. Treatment with a therapist for a few weeks is usually followed by a home exercise program which you continue on your own for at least several more weeks.
Your physician may also prescribe medications such as muscle relaxants, non-steroidal anti-inflammatory drugs such as aspirin or ibuprofen, pain relievers, or steroids. In addition, some patients get relief by applying moist heat or massaging the affected area.
When treatment begins in the early stages of neurogenic TOS, most patients improve with the measures listed above. However, if your TOS symptoms do not improve with these measures, and if your symptoms are interfering with sleep, work, recreation, or activities of daily living, your physician may consider more aggressive therapy. Your vascular surgeon may recommend TOS decompression surgery that involves removing certain muscles in your neck, removing your first rib, or a combined operation to remove both muscles and rib.
Surgery for thoracic outlet syndrome, however, is not without risks. There are many vital structures in this part of the body that can be injured during TOS decompression surgery. In addition, surgery does not always relieve the symptoms of neurogenic TOS. Larger studies evaluating outcomes from surgery for neurogenic TOS demonstrate that up to 70 percent of patients can have improvement in their symptoms, while 30 percent may feel no better or worse. In addition, approximately 10 to15 percent of patients that do have improvement will have recurrent symptoms within 1 to 2 years. Given these facts, and the often good response to conservative therapy, most surgeons do not recommend surgery as the initial treatment.
Venous TOS is not treated with physical therapy. Rather, the clot in the vein is initially treated with clot dissolving medication (called thrombolysis), with blood thinners (anticoagulants), or sometimes treated by surgically opening the vein and removing the clot. Once the clot has been removed, your surgeon may recommend that the first rib be removed so that the narrow space through which the vein passed can be enlarged to prevent the vein from clotting again. If the vein is badly narrowed, the narrow spot can be widened by having a balloon stretch out the vein, a procedure called an angioplasty. In some instances, the vein will be repaired operatively, at the time of the rib removal, with a patch (made from another vein) or with replacement of the diseased segment of vein.
Arterial TOS is treated in a very different way. If the subclavian artery in your thoracic outlet has become damaged by pressure, your vascular surgeon must repair the artery or replace it with an arterial graft. The replacement graft may be a vein from another part of your body or a plastic artery substitute. In addition to fixing the damaged artery, the abnormal rib must be removed to prevent the artery from being damaged again. Your vascular surgeon can perform all of this in one operation.
What can I do to stay healthy?
You can improve your recovery from TOS by practicing good posture, taking frequent breaks from work to stretch, and losing weight if you are overweight. Also, if you are prone to TOS, it is wise to avoid repetitive lifting of heavy objects over your head.
Images reproduced by kind permission Vascular Web