A familiarity with the anatomy of the neck and the thoracic outlet will help you to understand TOS. The thoracic outlet is the space in the neck through which pass the nerves to the arm (the brachial plexus), the artery to the arm, (subclavian artery) and the vein which drains the arm (the subclavian vein). All of these structures pass over the first rib and under the clavicle (collar bone). The vein is the forward most structure. The artery lies in the middle and the five nerves comprising the brachial plexus lie behind the artery. Between the vein and artery is the anterior scalene muscle. This muscle stretches from the lowest three cervical vertebrae to the front part of the first rib. However, the muscle also attaches to the covering over the top of the lung, around the front of the artery, and to the back of the vein. Additionally, it connects under the vein, artery, and lower most root of the brachial plexus to the middle scalene muscle and back of the rib. The importance of this anatomy will be discussed later. Behind the nerves, the middle scalene muscle connects the same lower 3 vertebrae to the back third of the first rib. Rarely, an additional rib is present. When this does occur, the”cervical rib” grows out of the lowest cervical vertebrae and attaches itself to the first rib. When this rib is present, it pushes the lowermost structures of the brachial plexus and the subclavian artery upward.
Thoracic Outlet Syndrome complaints can be caused by impingement on nerves, artery or vein.
Arterial TOS is the rarest form and is usually manifest by a clot in the arteries of the forearm or hand. The clot originates from the subclavian artery. In this case, a cervical rib has usually pushed on the artery from below resulting in damage and clot formation. If this problem is not corrected, the clots continue to travel downstream and eventually plug up the arteries causing symptoms of pain in the arm and a loss of the pulses in the wrist.
Venous TOS is also uncommon. It presents as a sensation of fullness and swelling in the entire arm .This may be noticed during or after strenuous exercise involving the arm, or a person may awaken with a swollen, bluish arm. The cause of venous TOS is the pinching of the vein at the base of the neck. An abnormally enlarged or mal-positioned muscle as it inserts under the first rib commonly causes the pinching of the vein.
Neurogenic TOS, by far the most common type of Thoracic Outlet Syndrome, is caused by impingement or compression of the nerves to the arm. It is also known as brachial plexus impingement. This type of problem almost always occurs in adults in the third through fifth decade of life. It may begin following injury such as a motor vehicle accident or a fall. It sometimes results from the injury of repetitive work It can begin without obvious cause. A person may complain of aching discomfort in the shoulder with numbness and tingling of the arm, forearm and some or all fingers. The symptoms often begin intermittently and progress to constant discomfort. One may feel clumsiness of the affected arm, dropping objects. Often fatigue of the arm and hand develops with use. Sometimes there is a band-like tightness around the biceps muscle. There may be a feeling as though the hand swells. Both hand and arm may feel cold as though there is decreased circulation. It may be difficult finding a comfortable position in which to sleep. One may awaken during the night with pain, aching, or numbness of the arm. Activities such as computer work, lifting, and driving, heavy housework, washing windows, putting dishes away, or performing repetitive activities can be aggravating. Overuse of the affected arm may result in increased discomfort. These symptoms are sometimes accompanied by headache, neck pain, shoulder and back muscle tightness or chest discomfort.
Besides Thoracic Outlet Syndrome, many other processes can cause neck, shoulder, and arm pain. It is the medical consultant’s task to determine whether there are other causes for the patient’s pain. Besides a detailed history and physical examination, specific tests may help sort out these other causes. Those tests may include but are not limited to x-rays of the neck, chest, and shoulder, scans of the neck, brachial plexus, or shoulder, electro diagnostic studies of the arm, and diagnostic blocks of the plexus or the scalene muscle.
The physical examination focuses on demonstrating that symptoms are caused by compression of one or more of the important thoracic outlet structures. During the physical examination, the patient is placed into positions, which might compress the brachial plexus. The affected arm is moved in order to place tension on individual nerves to determine whether those nerves are compressed.
Many reading this know all too well the symptoms of TOS. You may not, however know the cause of the discomfort. A probable cause of numbness, tingling and pain in the arm is compression and or impingement of the nerves by structures lying adjacent to the nerves, including bone, muscle and connective tissue. The anterior scalene muscle, the middle scalene muscle, or both contract and shorten due to injury or overuse. This muscle shortening narrows the outlet through which the nerves travel through. Muscles, connective tissue and bone now restrict nerve movement and irritate nerve tissue. Other muscles in the shoulder girdle also tighten in an effort to limit irritation of the plexus. But this results in soreness of these muscles of the neck, shoulder, and back. There is tremendous variation in the anatomy of the neck where the nerves exit. There may be fibrous or muscular bands which contribute to the constriction of the nerves. Proper nerve function also requires gliding of peripheral nerves as the arm moves. For example, with arm movement to full extension, the median nerve must elongate 45%. With elbow flexion the median nerve must slacken by 14% of its length. Chronic nerve compression causes fibrosis interfering with this longitudinal gliding.
There are physicians, even specialists who do not consider TOS to be a real diagnosis. We disagree. Those who dispute the existence of neurogenic TOS nevertheless accept that nerve compression and subsequent injury may occur all along the nerve from the cervical spine to the wrist. However, they fail to explain why compression may not occur at the thoracic outlet. There is no dispute that vein and artery in front of the nerves can be compressed. Lastly, these experts agree that nerve compression can be severe enough to cause muscles enervated by those nerves to atrophy. However, they fail to acknowledge that lesser degrees of compression in the thoracic outlet would cause pain and dysfunction without advanced muscle wasting. A final argument favoring the existence of TOS is relief of symptoms and improved function of the arm following successful surgical decompression, an occurrence we have witnessed repeatedly.
Options exist in the management of Thoracic Outlet Syndrome.
For each type of problem- venous, arterial and nerve impingement– there are non-surgical and surgical options.
When the subclavian artery has been injured by the bony and non-bony structures at the thoracic outlet the best treatment is surgery. It is important to decompress the artery removing the first and cervical ribs as well as any constricting connective and muscle tissue. The subclavian artery itself may need to be replaced or repaired so that no further clot forms. It is also necessary to consider removing any clot that has floated into the arm or hand.
When the subclavian vein is compressed it is at risk for thrombosis or clotting. The obstructing clot could break loose and travel to the lung causing a pulmonary embolus. Additionally, blockage of the subclavian vein lessens the channel through which blood returns from the arm to the heart. Just like a dam causes the river above the dam to swell, the blocked vein results in swelling of the arm. Collateral channels (other veins) enlarge over time to help empty the arm, but they are far less efficient than the large caliber subclavian vein. Thus, the arm remains swollen, and swelling worsens with use. With the passage of time, the clot in the vein changes from a Jell-O-like dissolvable substance to dense tissue which adheres to the vein wall and which may cause permanent blockage.
If recognized early, the fresh clot in the vein can be removed or lysed by placing a catheter into the vein and either removing the clot mechanically or chemically dissolving the clot with medicines dripped into the vein. If doctors are successful in opening up the vein, there still remains the extrinsic tissue which caused the compression of the vein in the first place. It has been our experience that surgical removal of the first rib along with muscular and connective tissue which compresses the vein from the outside provides the best chance of returning normal venous drainage to the affected arm. After successfully decompressing the subclavian vein, webs inside the vein caused by the clot or injury of the vein may have to be treated with a balloon to fully open up the inside the vein.
You are an important part of your treatment, and a successful outcome requires hard work on your part. Almost all patients are eager to do whatever they can to help their recovery. Since TOS symptoms begin at a definite point in time, it stands to reason that prior to that time sufficient space existed at the thoracic outlet to allow normal unimpeded nerve movement.
Therefore in the absence of something like a fractured rib or collar bone it may be possible to relax and stretch the muscular structures around the nerves and make the symptoms go away. This is done by physical and occupational therapists. The goal of therapy is:
1) To balance the muscles which pull the shoulder back with those that pull the shoulders forward.
2) To teach the patient ways of moving that do not further injure or strain the injured muscles.
3) To increase “core strength” improving the way one carries the shoulders neck and head.
4) To teach the patient to recognize tight muscles and to learn to relax them.
5) To slowly increase range of motion in a way so as not to irritate the nerves.
Treatment may include, massages by a trained therapist, a TENS unit to block the pain messages from the arm, and medicines to help relax tight muscles, to allow sleep, to combat swelling and inflammation, to lessen pain, and to treat depression. Patients have sought improvement through other means such as: biofeedback, acupuncture, meditation, chiropractic care, yoga, Pilates, and other therapies. We will try to help you find a therapist who is an expert in the treatment of brachial plexus disorders. Not all therapy is beneficial; some therapy can actually worsen symptoms. It should be given a thorough trial of at least 12 solid weeks and should include home exercises. When appropriate therapy has failed and when symptoms are intolerable, surgical decompression of the brachial plexus becomes a reasonable option.
Many surgical approaches to decompress the brachial plexus have been proposed. I will describe the technique used at the Vascular Institute of the Rockies and tell you why we believe it is the optimal surgical approach. We remove the first rib through a transaxillary approach (under the arm pit) as described by Dr. Roos.
If a cervical rib exists, it is also completely removed. We completely detach the anterior scalene muscle from the first rib as well as from the subclavian vein, artery, and attachments to the fascia beneath the subclavian artery, vein and brachial plexus. This allows the anterior scalene muscle to become completely relaxed, like a rubber band taken off stretch.
We believe that this complete dis-insertion of the anterior scalene muscle reduces the likelihood of recurrent symptoms to due scarring of the muscle. This is based on our observation when performing re-operations on patients in whom the muscle was not disconnected. At the back of the rib, we sew the cut end of the middle scalene muscle over the cut end of the first rib. This covers the rib and attaches the middle scalene muscle so it will not grow into the lower nerves of the plexus. We then carefully remove any impinging structures around the lower two or three nerve roots and the lower one or two trunks of the brachial plexus. We make every attempt not to disrupt the smooth surface of the scalene muscles adjacent to the nerves. We recognize that those surfaces facilitate nerve glide, and their dissection may lead to scar formation. We always use a mechanical arm holder so that no stretch injury occurs on the nerve.
Following surgery we emphasize rest and adequate pain control to allow the patient to relax. Gradually, physical therapy is implemented.
Patients are educated as to avoid future injury. Though complications can arise from this surgery, this is a safe and effective procedure when performed by surgeons who are experienced in treating TOS.
In some patients’ improvement is only temporary due to recurrent scar formation, which again entraps the plexus. The surgery is designed to limit scar formation by releasing the anterior and middle scalene muscles while still keeping the smooth surface of those muscles intact thus allowing nerve glide to continue. We believe that leaving the muscles in place while taking them off stretch is vital to achieving the best result from the surgery and makes our surgery different from others. Though few become completely symptom free after our TOS procedure, our goal is to lessen pain and discomfort, improve movement and function so that our patients can return to a productive and satisfying life.