Pathology (what can go wrong)
Any narrowing of these tunnels can compress the nerves with certain shoulder positions and produce symptoms. Shoulder movements that normally cause symptoms involve bringing the arm overhead, reaching at shoulder height or behind the body. Symptoms are characterized as numbness, pain, paresthesias (pins and needles) and a feeling of “deadness” in the arm that radiates into the hand. The outside of the hand (opposite the thumb side) is typically affected.
Neck motion can also cause impingement if the nerves are caught in the first tunnel (scalenus anticus and medius). Typically, with this entrapment, turning the head to the symptomatic side can bring on the symptoms. If the symptoms are brought about by looking up (cervical extension) without lifting the shoulder, the disorder more likely than not is from compression of the nerves in the neck (radiculopathy) and not in the shoulder (thoracic outlet syndrome).
Cervical ribs are extra ribs that have formed congenitally (in the womb) and occur in less than one percent of the population. These ribs are typically identified on an X-ray. If cervical ribs are present, these ribs can crowd out the nerves and artery in the first or second tunnels. The presence of these extra ribs does not mean that one will have thoracic outlet syndrome as less than ten percent of patients with these ribs have thoracic outlet symptoms.
It is very rare that motor strength is diminished by thoracic outlet syndrome as the sufferer will stop whatever activity is causing the symptoms and the compression injury to the nerves is short lived. In very severe cases however, muscle weakness can occur.
The symptoms can become so severe that simply holding the arms on a steering wheel can produce pain and numbness. Some patients complain that the arm “goes dead” in this position. Sleeping can be a challenge to some as inadvertently, these individuals sleep with their arm overhead or the shoulder “scrunched up” under the pillow, which then compresses the brachial plexus. These nerve symptoms can cause the patient to awaken in the middle of the night.
The symptoms that occur when the brachial plexus nerves are compressed are very similar to the “funny bone” (ulnar) nerve at the elbow becoming compressed. Everyone has had the experience that resting the inside of their elbow on a hard surface for a long period of time will cause the typical numbness and pins and needles to radiate into the outside of the hand as the hand “falls asleep”. These symptoms occur due to pressure on the ulnar nerve at the elbow. Pressure prevents nerve conduction.
An interesting fact is that this same ulnar nerve (which originates in the shoulder) is also the typical nerve that is most affected with compression in the thoracic outlet. This is due to the fact that the ulnar nerve originates from the lower roots of the brachial plexus. These lower roots are stretched a longer distance with overhead activity (like a cable that runs over a pulley). This is similar to a track star that runs the race on the outside of the track. He or she has to run a longer distance than the runner on the inside of the track if this individual stays in the outside lane.
Diagnosis of Thoracic Outlet Syndrome
Diagnosis is made with a thorough history, physical examination and the use of imaging studies. Differential diagnosis has to consider compression of the nerves in the neck (radiculopathy) as a cause of symptoms.
There are physical examination tests that can indicate the presence of thoracic outlet syndrome. The three main tests are called the “Roos”, “Wright’s” and “Adson’s” tests. Two of the tests “(Wright’s” and “Adson’s”) depend upon loss of the pulse of the brachial artery. This loss of pulse is unfortunately not a great indicator of presence of thoracic outlet syndrome but is helpful in the general diagnosis.
X-rays of the neck and shoulder are taken to make sure there are no cervical ribs and no old healed fractures of the clavicle that could produce a bony compression in the tunnel. An MRI of the neck is performed if there is any evidence of spinal nerve involvement. Occasionally, an MRI of the shoulder is ordered to make sure there are no very rare nerve root tumors or a Pancoast tumor (a tumor at the top of the lung that can also cause this syndrome).
Nerve conduction tests (EMGs and NCVs) are not generally useful in the diagnosis of this disorder as motor strength is very rarely diminished (which will produce negative EMGs) and the nerve bundle cannot be tested for conduction speed across the brachial plexus (the NCV test).
Treatment of Thoracic Outlet Syndrome
Treatment is a physical therapy program or chiropractic treatment that stretches the muscles, mobilizes the clavicle and eliminates the faults in motion of the shoulder. Occasionally, steroid injections can be helpful. Surgery is only called for in severe cases.
For more resources on thoracic outlet syndrome, or to determine your treatment options, please contact the practice of Dr. Donald Corenman, neck doctor and spine specialist serving the communities of Vail, Aspen, Denver and Grand Junction, Colorado.