Thoracic Outlet Syndrome

Thoracic outlet syndrome (TOS) consists of a group of distinct disorders involving compression at the superior thoracic outlet that affect the brachial plexus (nerves that pass into the arms from the neck), and/or the subclavian artery or vein (blood vessels that pass between the chest and upper extremity).

The compression may be positional (caused by movement of the clavicle (collarbone) and shoulder girdle on arm movement) or static (caused by abnormalities or enlargement of the various muscles surrounding the arteries, veins, and brachial plexus).

Types

There are three main types of TOS, named according to the cause of the symptoms:

• neurogenic TOS or NTOS, disorders produced by compression of the components of the brachial plexus nerves.
• arterial TOS, caused by compression of the subclavian artery.
• venous TOS, caused by compression of the subclavian vein.

The neurogenic form of TOS accounts for 95% of all cases of TOS.

It is known from pathological studies of cadavers, and from surgical studies of patients with TOS, that there are numerous anomalies of the scalene muscles and other muscles that surround the arteries, veins and brachial plexus. TOS may result from these anomalies, or also from enlargement (hypertrophy) of the scalene muscles. One common cause of hypertrophy is trauma, which may occur in traffic collisions.

The two groups of people most likely to develop TOS are those suffering from neck injuries from traffic collisions and those who use computers in non-ergonomic postures for extended periods of time. Other groups which may develop TOS, but significantly less frequently, are athletes who frequently raise their arms above the head (such as swimmers, volleyball players, baseball pitchers, and weightlifters), and also some musicians.

Classification

The following taxonomy of TOS is used in ICD-9-CM and older sources:

• Scalenus anticus 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.

A more modern system of classification is provided on the website of the National Institute of Neurological Disorders and Stroke (NINDS).

Diagnosis

Adson's sign and the costoclavicular maneuver are notoriously inaccurate, and may be a small part of a comprehensive history and physical examination of a patient with TOS. There is currently no single clinical sign that makes the diagnosis of TOS with certainty. Arteriography, while only rarely used to evaluate thoracic outlet syndrome, may be used if a surgery is being planned to correct an arterial TOS. Additional maneuvers that may be abnormal are the "hand raise" (holding both hands over head, the affected hand will often be paler than the unaffected because of compromised blood supply) and the "compression test" (pressure between the clavicle and medial humeral head causes radiation of pain / numbness into the affected arm).

Treatment

Continued and active postural changes along with acupuncture, physiotherapy or massage therapy may suffice. The recovery process however is long term, and a few days of poor posture can often set one back.

About 10 to 15% of patients undergo surgical decompression following an appropriate trial of conservative therapy, most often specific physical therapy directed towards the treatment of thoracic outlet syndrome, and usually lasting between 6 and 12 months. Surgical treatment may include removal of anomalous muscles, removal of the native anterior and/or middle scalene muscles, removal of the first rib or, if present, a cervical rib, or neurolysis (removal of fibrous tissue from the brachial plexus).

Noninvasive

Stretching

• The goal of self stretching is to relieve compression in the thoracic cavity, reduce blood vessel and nerve impingement, and realign the bones, muscles, ligaments, and tendons causing the problem.
• Moving shoulders forward (hunching) then back to neutral, followed by extending them back (arching) then back to neutral, followed by lifting shoulders then back to neutral.
• Tilting and extending neck opposite to the side of injury while keeping the injured arm down or wrapped around the back.

Nerve Gliding

• This syndrome causes a compression of a large cluster of nerves, resulting in the impairment of nerves throughout the arm. By performing nerve gliding exercises one can stretch and mobilize the nerve fibers. Chronic and intermittent nerve compression has been studied in animal models, and has a well-described pathophysiology, as described by Susan Mackinnon, MD, currently at Washington University in St. Louis. Nerve gliding exercises have been studied by several authorities, including David Butler in Australia.
• Extend your injured arm with fingers directly outwards to the side. Tilt your head to the otherside, and/or turn your head to the other side. 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.

Posture

• TOS is rapidly aggravated by poor posture. Active breathing exercises and ergonomic desk setup can both help maintain active posture. Often the muscles in the back become weak due to prolonged (years) hunching.

Ice/Heat

• Ice can be used to decrease inflammation of sore or injured muscles. Heat can also aid in relieving sore muscles by improving circulation to them. While the whole arm generally feels painful, some relief can be seen when ice/heat is applied to the thoracic region (collar bone, armpit, or shoulder blades).

Invasive

Cortisone

• Injected into a joint or muscle, cortisone can help relief and lower inflammation.

Botox injections

• Short for Botulinum Toxin A, Botox binds 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 unfortunately not covered by most medical 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 of a 'scalene block' is vital to determining the benefit and risk of using Botox.

Surgical approaches have also been used.

• Some physicians advocate the injection of a short-acting anesthetic such as xylocaine into the anterior scalene, subclavius, or pectoralis minor muscles as a provocative test to assist in the diagnosis of thoracic outlet syndrome. This is referred to as a 'scalene block'. However, this is not considered a 'treatment', as the relief is expected to wear off within an hour or two, at a maximum. Active research continues into the accuracy and risks of this provocative test.