Thoracic outlet syndrome or TOS is an uncommon group of disorders that cause pain or weakness in the arm and shoulder. The condition can affect anyone but is diagnosed more often in women, those between the ages of 20 and 50, and athletes or people in jobs that require repetitive motions. TOS is not a life-threatening disorder, but it can be difficult to diagnose because the symptoms mimic those of several other conditions.
The Definition of Thoracic Outlet Syndrome
The cause of thoracic outlet syndrome is compression, injury, or irritation of the nerves and blood vessels in the upper chest, below the neck, and between the collarbone and the first rib. The thoracic outlet is the rigid, narrow space between the lower neck and upper chest. The subclavian artery, subclavian vein, and brachial plexus nerve bundle pass through this space. If the collarbone slips down and forward, the thoracic outlet narrows and puts pressure on these nerves and blood vessels, leading to the symptoms of TOS.
Types of TOS
There are three types of thoracic outlet syndrome, but all three consist of a narrowed thoracic outlet space and scar formation.
- Neurogenic TOS is the most common, occurring in about 90% of cases. It develops when there is compression of the nerves in the neck that lead to the arm.
- Venous TOS happens when a vein is compressed and causes a blood clot in the upper body. Only about five percent of cases receive this diagnosis.
- Arterial TOS is the rarest type of TOS. It is caused by the compression of an artery.
- Sometimes, venous and arterial TOS occur together, causing vascular thoracic outlet syndrome.
Injuries and Conditions that Cause TOS
Most cases of thoracic outlet syndrome are due to poor posture or injury. Individuals who experience physical trauma from a car or motorcycle accident may develop the condition, and whiplash can lead to late-onset TOS symptoms after the immediate whiplash issues heal. A first rib or collarbone injury can also cause TOS, as can excessive weight gain and obesity, which increase fatty tissue in the neck, compress the nerves or subclavian vessels, and put pressure on the joints. Women who experienced mild TOS may notice their symptoms increase if they become pregnant. In rare cases, a tumor in the neck or enlarged lymph nodes in the upper chest or underarm areas can cause compression.
Work-Related Causes of TOS
Activities that include repetitive overhead motions, or lifting, carrying, or pulling heavy objects can lead to thoracic outlet syndrome. These motions cause inflammation or swelling, which puts pressure on the nerves and blood vessels. Hairdressers, dental hygienists, painters, and auto mechanics often develop the condition. Shelf stockers, factory line workers, and those who spend their days typing are also more susceptible. Anyone who maintains an awkward or prolonged posture to perform their work duties is at risk.
Sports-Related Causes of TOS
Volleyball, baseball, swimming, wrestling, dancing, and golf require repetitive movements, which can lead to overuse and TOS. Individuals who participate in weightlifting and bodybuilding are also more likely to develop the syndrome. The muscles in bodybuilders’ necks increase in size to the point where they can compress the nerves or subclavian vessels. Weightlifters repeatedly lift heavy objects. Sports medicine experts advise against suddenly increasing the intensity of workouts — such abrupt enhancements can lead to injuries and TOS.
Congenital Causes of TOS
Congenital abnormalities can also cause TOS and are the most serious, but only a small number of people develop the condition for this reason. These abnormalities generally occur in the womb and may not be noticeable until years later. About one in 500 people develop an extra rib just above the first rib on either side or both sides of the body. This is a cervical rib or neck rib. The cervical rib can compress or irritate the subclavian artery and cause TOS. Additionally, some individuals are born with another muscle in their necks or abnormal collarbones that make them more susceptible to TOS.
Symptoms of TOS
The signs and symptoms of thoracic outlet syndrome vary, depending on the type of disorder.
- Those with neurogenic TOS experience hand numbness or weakness and a reduction in the size of their hand muscles. This usually occurs on one side of the body. They may feel pain, tingling, numbness, or weakness in the chest, neck, and arms as well.
- Venous TOS usually causes a sudden onset of symptoms soon after a tiring exercise. People experience swelling of the hands, fingers, and arms. The veins in the front chest wall may also swell.
- Arterial TOS is the most serious and is usually due to congenital abnormalities or a blood clot in the subclavian artery. Symptoms include poor blood circulation, numbness, and coldness in the arms, hands, and fingers. Individuals sometimes develop finger sores as well.
Other Conditions With Similar Symptoms
Rotator cuff injuries, fibromyalgia, spinal cord tumors, multiple sclerosis, and cervical disc disorders, to name only a few, present with many of the same symptoms as TOS. Some people mistake chest pain symptoms of TOS with angina or chest pain due to heart issues. However, TOS chest discomfort does not increase with movement, while angina often does. TOS occurs only in about eight percent of the population.
Diagnosis of TOS
There is a wide controversy within the medical community concerning the diagnosis of TOS, primarily because its symptoms are so similar to other conditions and disorders. Doctors reach a diagnosis through a process of elimination. They will usually discuss the individual’s medical history first. Then, to determine if there are any movement issues, they perform stress maneuver testing and try to cause the symptoms the individual is reporting. The physician usually performs an ultrasound, MRI, or chest X-ray. If they suspect neurogenic TOS, they may perform a brachial plexus block, which requires injecting a local anesthetic into the neck muscles. If the pain goes away, the individual is likely experiencing TOS.
The primary treatment for neurogenic TOS is physical therapy. The goal is to help the individual regain their range of motion, improve their posture, and strengthen muscles. For those who continue to feel pain, the physician will usually recommend over-the-counter pain medications before prescribing pharmaceuticals such as muscle relaxants. Neurogenic TOS may require surgery if physical therapy is ineffective. Doctors prescribe blood thinners for venous TOS, and these patients may also require surgery to correct the narrowing and compression of the veins. Arterial TOS usually requires surgery to remove the neck rib and repair any structural issues with the artery.