出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/10/28 10:32:18」(JST)
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| Thoracic Outlet Syndrome (TOS) | |
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| Classification and external resources | |
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.
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| ICD-10 | G54.0 |
| ICD-9 | 353.0 |
| DiseasesDB | 13039 |
| MedlinePlus | 001434 |
| eMedicine | pmr/136 |
| MeSH | D013901 |
Thoracic outlet syndrome (TOS) is a syndrome involving compression at the superior thoracic outlet[1] resulting from excess pressure placed on a neurovascular bundle passing between the anterior scalene and middle scalene muscles.[2] 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, which does not normally pass through the scalene hiatus.
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.[3]
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 aetiologies, first rib fixations, scalene muscle spasm, and a cervical rib or fibrous band.
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 cerebrovascular arterial insufficiency when affecting the subclavian artery.[4] It also can affect the vertebral artery, in which case it could produce transient blindness,[5] and embolic cerebral infarction.[6]
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.
Painful TOS can be attributed to one or several etiological factors:[7]
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 the "stick em up hand raise" for up to 3–5 minutes, which involves holding both hands at right angles over the head bent at the elbows, with or without opening and closing of the fingers (a positive test occurs when the affected hand quickly becomes paler than the unaffected because of compromised blood supply), and the "compression test", when exerting pressure between the clavicle and medial humeral head causes radiation of pain and/or numbness into the affected arm.[8]
Doppler Arteriography, with probes at the fingertips and arms, tests the force and "smoothness" of the arterial 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.[9] 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.
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 protean.[10] http://www.tos-syndrome.com/old1/newpage12.htm[11]
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.
One cause of arterial compression is trauma, and a recent case involving fracture of the clavicle has been reported[13]
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.[citation needed] 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, shuttlecock players, baseball pitchers, and weightlifters), rock climbers, electricians who work long hours with their hands above their heads, and some musicians.
It is also possible to classify TOS by the location of the obstruction:
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.
Most people respond to conservative measures such as medications, rest, chiropractic, occupational therapy, physical therapy, and massage, and stretching. Only a minority of patients with signs and symptoms of TOS ultimately proceed to surgery.[citation 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.
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).
Cortisone injected into a joint or muscle can help lower inflammation and provide relief.[dubious – discuss] Botox injections bind nerve endings and prevents the release of neurotransmitters that activate muscles. A small amount of Botox injected into the tight or spastic muscles (usually one or all three scalenes) found in TOS sufferers often provides months of relief while the muscle is temporarily paralyzed. This noncosmetic treatment is not covered by most medical insurance plans and costs upwards of $400. The relief of symptoms from a Botox injection generally lasts 3–4 months, at which point the Botox toxin is degraded by the affected muscles. Serious side effects have been reported and are similarly long-lasting, so improved understanding of the mechanism this form of 'scalene block' is vital to determining iks risk/benefit profile. Additionally, many patients in a study done at Johns Hopkins Hospital in Baltimore report no relief of symptoms from Botox or scalene injections, which may indicate that the pain does not stem from the scalene muscle and may not be TOS. Botox can be an effective treatment for neurogenic TOS.[14] It may eliminate pain or reduce it enough for the victim to undergo physical therapy and, hopefully, be able to properly stretch and reduce compression in the affected area.
Surgical approaches have also been used successfully in TOS.[15] In cases where 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 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.
Major League Baseball players such as St. Louis Cardinals Starting Pitcher Chris Carpenter,[16] Dodgers SP Josh Beckett, Mets SP Shaun Marcum,[17] Rangers SP Matt Harrison,[18] and former Giants SP Noah Lowry[19] have recently been diagnosed with thoracic outlet syndrome.
Musician Isaac Hanson suffered a potentially life-threatening pulmonary embolism as a complication of thoracic outlet syndrome.[20]
UFC fighter Matt Serra had a rib removed to alleviate TOS.[21]
Boston Bruins defenseman Adam McQuaid was diagnosed with TOS in September 2012 and as a result was nominated for the Bill Masterton Memorial Trophy.[22]
The Japanese band Maria disbanded in 2010 due to drummer Tattsu's TOS which made it impossible for her to continue playing.[23]
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| リンク元 | 「前斜角筋症候群」「斜角筋症候群」「neurogenic thoracic outlet syndrome」 |
| 関連記事 | 「scalenus」「syndrome」 |
斜角筋の異常による神経や血管の圧迫と腕神経叢絞扼