A Physician's Guide to Diagnosis of Thoracic Outlet SyndromeWhen a patient presents with symptoms of arm pain, cold limb, swelling in the arm, and/or tenderness in the armpit or above the collar bone, the physician may suspect one of several problems. Sorting through all the symptoms, the patient's history, and conducting a physical exam may help rule out (or rule in) various possible causes. This result of this process (and even the process itself) is called the differential diagnosis.
One of the main causes of symptoms like this is called thoracic outlet syndrome (TOS). Thoracic outlet syndrome (TOS) can cause pain and numbness in the shoulder, arm, and hand. But testing for TOS is difficult. There is no one test to accurately diagnose TOS, and other conditions can have similar symptoms. Patients may need to go through several tests to find out if TOS is actually the cause of the pain. Making the right diagnosis often takes time and can be a cause of frustration, both for the patient and for the doctor.
That's why Dr. Richard M. Braun an orthopedic surgeon from San Diego, California wrote this guide to the diagnosis of TOS for other physicians. By reviewing the typical history and clinical presentation (patient's signs and symptoms), the physician is better able to decide what imaging studies or other diagnostic tests are needed. Understanding the cause of the problem is also important.
The main cause of TOS is that the nerves and blood vessels going to the arm and hand get squeezed near the thoracic outlet. The thoracic outlet is this opening between the scalene (neck) muscles and the rib cage. The nerves and blood vessels then go under the collarbone (also known as the clavicle), through the armpit (the axilla), and down the arm to the hand.
Thoracic outlet syndrome can occur for many reasons. For example, pressure on nerves and vessels can happen in anyone who has fractured the clavicle. It can also happen in people who have an extra first rib, although this doesn't always result in TOS.
Extra muscle or scar tissues in the scalene muscles can put extra pressure on the nerves and arteries. Heavy lifting and carrying can bulk up the scalenus muscles to the point where the nerve and arteries get squeezed. Traumatic injury from a car accident can also cause problems that lead to TOS. In an accident, the shoulder harness of the seat belt can strain or tear the muscles. As they heal, scar tissue can build up, putting pressure on the nerves and blood vessels at the thoracic outlet.
Neck and arm positions used at work and home may contribute to TOS. People who have to hold their neck and shoulders in awkward alignment sometimes develop TOS symptoms. TOS symptoms are also reported by people who tilt the head and neck repeatedly or who have to hold their arms up or out for long periods of time.
That all sounds so easy and straightforward but in fact, the symptoms can be very confusing. This is especially true when more than one anatomical structure is being compressed (e.g., nerves and blood vessels). Surgeons rely on X-rays, MRIs, arteriography and venography (studies of blood vessels), and Doppler studies (tests of blood circulation) to provide additional helpful and diagnostic information.
Circulation problems can also be seen when certain tests are applied. The patient is put in positions that provoke or produce blood loss such as lifting the arms overhead. They hold the position for three minutes and the examiner monitors whether symptoms are aggravated by this approach and how quickly blood supply returns to the arm and hands.
Other tests that can be ordered include electrodiagnostic tests (nerve conduction velocity, electromyography or EMG) and physiologic and functional capacity tests. Muscle blocks can also be done to prevent muscles (like the scalenes) from contracting fully. The injection weakens the scalene muscle enough that it can no longer pull the first rib up against the nerves and blood vessels passing through the thoracic outlet. Such a test helps identify overused muscles that might be a problem.
A special work simulation machine can be used after a muscle block to mimic the type of work patients are doing on-the-job. If the symptoms are reduced or even gone after the injection, then positions used at work are likely contributing to the problem.
The author concludes by suggesting that the examining physician gather all the data needed to identify the cause of symptoms typical of TOS first before doing anything else. This includes the history, results of the physical exam, and results of the additional studies ordered. Once the data is analyzed, it may be clear how the information falls into line and points to a specific diagnosis. An accurate and objective diagnosis is essential to improved treatment outcomes.
Richard M. Braun, MD. Thoracic Outlet Syndrome: A Primer on Objective Methods of Diagnosis. In The Journal of Hand Surgery. September 2010. Vol. 35A. No. 9. Pp. 1539-1541.
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