Thoracic outlet syndrome
||This article possibly contains original research. (November 2009)|
|Thoracic outlet syndrome (TOS)|
The right brachial plexus, viewed from in front. In thoracic outlet syndrome there is compression of the brachial plexus or subclavian vessels in their passage from the cervical and upper thoracic area toward the axilla and proximal arm. The anterior supraclavicular neurosurgical procedure is used to treat certain refractory cases.
|Classification and external resources|
|Patient UK||Thoracic outlet syndrome|
Thoracic outlet syndrome (TOS) is a syndrome involving compression at the thoracic inlet, which is known clinically as the superior thoracic outlet resulting from excess pressure placed on a neurovascular bundle passing between the anterior scalene and middle scalene muscles. It can affect one or more of the nerves that innervate the upper limb and/or blood vessels as they pass between the chest and upper extremity, specifically in the brachial plexus, the subclavian artery, and rarely, the subclavian vein.
TOS may result from a positional cause, for example, by abnormal compression from the clavicle (collarbone) and shoulder girdle on arm movement. There are also several static forms, caused by abnormalities, enlargement, or spasm of the various muscles surrounding the arteries, veins, and/or brachial plexus, a fixation of a first rib, or a cervical rib. A Pancoast tumor (a rare form of lung cancer in the apex of the lung) can lead to thoracic outlet syndrome in the progressive stages of the disease. The most common causes of thoracic outlet syndrome include physical trauma from a car accident, repetitive strain injury from a job such as frequent nonergonomic use of a keyboard, sports-related activities, and anatomical defects such as having an extra rib. In pregnancy, if a narrow superior thoracic outlet exists previously, the patient can have symptoms for the first time. Joints loosen during pregnancy, making it easier to develop bad posture.
Common orthopaedic tests used are the Adson's test, the Costoclavicular Manoeuvre, and the "Hands-Up" test or "EAST" test. Careful examination and X-ray are required to differentially diagnose between the positional and static etiologies, first rib fixations, scalene muscle spasm, and a cervical rib or fibrous band.
Signs and symptoms
TOS affects mainly the upper limbs, with signs and symptoms manifesting in the arms and hands. Pain is almost always present and can be sharp, burning, or aching. It can involve only part of the hand (as in the 4th and 5th finger only), all of the hand, or the inner aspect of the forearm and upper arm. Pain can also be in the side of the neck, the pectoral area below the clavicle, the armpit/axillary area, and the upper back (i.e., the trapezius and rhomboid area). Decoloration of the hands, one hand colder than the other hand, weakness of the hand and arm muscles, and tingling are commonly present.
TOS is often the underlying cause of refractory upper limb conditions like frozen shoulder and carpal tunnel syndrome that frequently defy standard treatment protocols. TOS can be related to Forward head posture.
A painful, swollen and blue arm, particularly when occurring after strenuous physical activity, could be the first sign of a subclavian vein compression related with an unknown TOS and complicated by thrombosis, the so-called Paget–Schroetter syndrome or effort-induced thrombosis.
TOS can be related to cerebrovascular arterial insufficiency when affecting the subclavian artery. It also can affect the vertebral artery, in which case it could produce vision disturbances, including transient blindness, and embolic cerebral infarction.
TOS can also lead to eye problems and vision loss as a circumstance of vertebral artery compression. Although very rare, if compression of the brain stem is also involved in an individual presentation of TOS, transient blindness may occur while the head is held in certain positions.
If left untreated, TOS can lead to neurological deficits as a result of the hypoperfusion and hypometabolism of certain areas of the brain and cerebellum.
Painful TOS can be attributed to one or more of the following factors:
- Congenital abnormalities are frequently found in persons with TOS. These include cervical rib, prolonged transverse process, and muscular abnormalities (e.g., in the scalenus anterior muscle, a sickle-shaped scalenus medius) or fibrous connective tissue anomalies.
- Trauma (e.g., whiplash injuries) or repetitive strain is frequently implicated.
- Rarer acquired causes include tumors, hyperostosis, and osteomyelitis
Adson's sign and the costoclavicular maneuver lack specificity and sensitivity and should comprise only a small part of the mandatory comprehensive history and physical examination undertaken with a patient suspected of having TOS. There is currently no single clinical sign that makes the diagnosis of TOS with any degree of certainty.
Additional maneuvers that may be abnormal in TOS include Wright's Test, which involves hyperabducting the arms over the head with some extension and evaluating for loss of radial pulses or signs of blanching of the skin in the hands indicating a decrease in blood flow with the maneuver. The "compression test" is also used, exerting pressure between the clavicle and medial humeral head causes radiation of pain and/or numbness into the affected arm.
Doppler arteriography, with probes at the fingertips and arms, tests the force and "smoothness" of the blood flow through the radial arteries, with and without having the patient perform various arm maneuvers (which causes compression of the subclavian artery at the thoracic outlet). The movements can elicit symptoms of pain and numbness and produce graphs with diminished arterial blood flow to the fingertips, providing strong evidence of impingement of the subclavian artery at the thoracic outlet. Doppler arteriography does not utilize probes at the fingertips and arms, and in this case is likely being confused with plethysmography, which is a different method that utilizes ultrasound without direct visualization of the affected vessels. It should also be noted that Doppler ultrasound (not really 'arteriography') would not be used at the radial artery in order to make the diagnosis of TOS. Finally, even if a Doppler study of the appropriate artery were to be positive, it would not diagnose neurogenic TOS, by far the most common subtype of TOS. There is plenty of evidence in the medical literature to show that arterial compression does not equate to brachial plexus compression, although they may occur together, in varying degrees. Additionally, arterial compression by itself does not make the diagnosis of arterial TOS (the rarest form of TOS). Lesser degrees of arterial compression have been shown in normal individuals in various arm positions and are thought to be of little significance without the other criteria for arterial TOS.
By structures affected and symptomatology
There are three main types of TOS, named according to the cause of the symptoms; however, these three classifications have been coming into disfavor because TOS can involve all three types of compression to various degrees. The compression can occur in three anatomical structures (arteries, veins and nerves), it can be isolated, or, more commonly, two or three of the structures are compressed to greater or lesser degrees. In addition, the compressive forces can be of different magnitude in each affected structure. Therefore, symptoms can be variable.
- Neurogenic TOS includes disorders produced by compression of components of the brachial plexus nerves. The neurogenic form of TOS accounts for 95% of all cases of TOS.
- Arterial TOS is due to compression of the subclavian artery.
- Venous TOS is due to compression of the subclavian vein.
There are many causes of TOS. The most frequent cause is trauma, either sudden (as in a clavicle fracture caused by a car accident), or repetitive (as in a legal secretary who works with his/her hands, wrists, and arms at a fast paced desk station with non-ergonomic posture for many years). TOS is also found in certain occupations involving lots of lifting of the arms and repetitive use of the wrists and arms.
The two groups of people most likely to develop TOS are those suffering from neck injuries due to traffic accidents and those who use computers in non-ergonomic postures for extended periods of time. TOS is frequently a repetitive stress injury (RSI) caused by certain types of work environments. Other groups which may develop TOS are athletes who frequently raise their arms above the head (such as swimmers, volleyball players, dancers, badminton players, baseball pitchers, and weightlifters), rock climbers, electricians who work long hours with their hands above their heads, and some musicians.
By structure causing constriction
It is also possible to classify TOS by the location of the obstruction:
- Anterior scalene syndrome (compression on brachial plexus and/or subclavian artery caused by muscle growth) – diagnosed by using Adson's sign with patient's head turned outward.
- Cervical rib syndrome (compression on brachial plexus and/or subclavian artery caused by bone growth) – diagnosed by using Adson's sign with patient's head turned inward.
- Costoclavicular syndrome (narrowing between the clavicle and the first rib) – diagnosed with the costoclavicular maneuver.
Some people are born with an extra incomplete and very small rib above their first rib, which protrudes out into the superior thoracic outlet space. This rudimentary rib causes fibrous changes around the brachial plexus nerves, inducing compression and causing the symptoms and signs of TOS. This is called a "cervical rib" because of its attachment to C-7 (the 7th cervical vertebra), and its surgical removal is almost always recommended. The symptoms of TOS can first appear in the early teen years as a child is becoming more athletic.
Evidence for the treatment of thoracic outlet syndrome as of 2014 is poor. Some people respond to conservative measures such as medications, rest, and physical therapy. Surgery is rarely needed.
Stretching and physical therapy are common noninvasive approaches used in the treatment of TOS. The goal of stretching is to relieve compression in the thoracic cavity, reduce blood vessel and nerve impingement, and realign the bones, muscles, ligaments, and/or tendons that are causing the problem.
- One commonly prescribed set of stretches includes moving the shoulders anteriorly (forward – called "hunching"), then back to a neutral position, then extending them posteriorly (backward, called "arching"), then back to neutral, followed by lifting the shoulders up as high as possible, and then back down to neutral, repeated in cycles as tolerated.
- Another set of stretches involves tilting and extending the neck opposite to the side of the injury while keeping the injured arm down or wrapped around the back.
- Physical therapy can include passive or active range of motion exercises, working up to weighted or restricted sets (as tolerated).
- Physical therapy usually consists of mobilization of any or all of the articulations of the shoulder girdle, including the 1st rib, additional myofascial release (MFR) or Active Release Technique (ART) to the connected musculature, and use of passive or active range-of-motion exercises.
- Nerve gliding can be performed by extending the injured arm with fingers directly outwards to the side and tilting the head to both sides. A gentle pulling feeling is generally felt throughout the injured side. Initially, only do this and repeat. Once this exercise has been mastered and no extreme pain is felt, begin stretching your fingers back. Repeat with different variations, tilting your hand up, backwards, or downwards.
TOS is rapidly aggravated by poor posture. Active breathing exercises and ergonomic desk setup and motion practices can help maintain active posture. Often the muscles in the back become weak due to prolonged (years of) "hunching" and other poor postures.
Ice can be used to decrease inflammation of sore or injured muscles. Heat can also aid in relieving sore muscles by improving blood circulation to them. While the whole arm generally feels painful in TOS, some relief can be seen when ice or heat is intermittently applied to the thoracic region (collar bone, armpit, or shoulder blades).
Surgical approaches have also been used successfully in TOS. In cases where the first rib (or a fibrous band extending from the first rib) is compressing a vein, artery, or the nerve bundle, the first rib and scalene muscles and any compressive fibrous tissue can be removed. This procedure is called a First rib resection and scalenectomy and involves going through the underarm area, above the collarbone, or back of the neck area and removing the first rib, scalene muscles, and any compressive fibrous tissue to open the area to allow increased blood flow and/or reduce nerve compression. In some cases there may be a rudimentary rib or a cervical rib that can be causing the compression, which can be removed using the same technique.
Physical therapy is often used before and after the operation to decrease recovery time and improve outcomes. Potential complications include pneumothorax, infection, loss of sensation, motor problems, subclavian vessel damage, and, as in all surgeries, a very small risk of permanent serious injury or death.
Several Major League Baseball players, especially pitchers, have been diagnosed with thoracic outlet syndrome, including St. Louis Cardinals starting pitchers Chris Carpenter and Jaime Garcia, Los Angeles Dodgers SP Josh Beckett, Cleveland Indians SP Shaun Marcum, Texas Rangers SP Matt Harrison, and former Giants SP Noah Lowry. Starting pitcher Chris Young, who previously struggled with shoulder problems, underwent surgery for TOS in 2013 and felt "completely different" post-recovery. Young exceeded expectations on his return to the major leagues at age 35, becoming a valuable member of the 2014 Seattle Mariners' starting rotation.
- May–Thurner syndrome – a similar compressive pathology involving the left common iliac vein
- Backpack palsy – a similar compressive pathology involving the long thoracic nerve, or adjacent brachial plexis nerves
- Thoracic outlet syndrome at the US National Library of Medicine Medical Subject Headings (MeSH)
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