Thoracic Outlet Syndrome (TOS)

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What is thoracic outlet syndrome?

Thoracic outlet syndrome (TOS) is a term applied to several conditions that share a common feature: compression of neurovascular structures in the thoracic outlet. The term “thoracic outlet” refers to the area above and behind the clavicle (collarbone) that extends from the neck to the shoulder and forms an "outlet" through which blood vessels and nerves pass before they enter the upper extremities. Symptoms can include pain, weakness, fatigue, cold feeling in the arm, shoulder, or hands, as well as numbness or tingling in the fingers.

What are the different types of thoracic outlet syndrome?

Not all doctors agree on all of the various types, except for true neurogenic thoracic outlet syndrome. Others are more controversial.

1. True neurogenic thoracic outlet syndrome usually presents with one-sided symptoms, often initiated by pain, numbness and painful paresthesias (sensations in the skin that have no obvious external cause, such as a tingling or burning feeling). Patients typically have weaknesses in intrinsic hand muscles (muscles in the hand itself, rather than those in the wrist or forearm which also control hand movement), which can result in loss of dexterity and eventually muscle atrophy. This type of TOS has clear and well recognized clinical and electrophysiologic features that can be objectively identified by your doctor with the use of specialized electrodiagnostic and imaging tests including, electromyography (EMG) and magnetic resonance neurography. This subtype is typically caused by a fibrous band extending from the first thoracic rib to a cervical (C7) rib or elongated transvers process at C7. A diagnosis for this condition is usually confirmed when an EMG test objectively demonstrates a patient's neurological deficits.
2. Vascular thoracic outlet syndrome This is more controversial. Some doctors even dispute that it exists. It is more difficult to objectively demonstrate.
3. A third TOS category exists where patients may experience vascular or neurological symptoms, or even simply pain, but where neurological and vascular testing return normal results. This can be a very difficult diagnosis to make.

What causes thoracic outlet syndrome?

TOS is caused by compression on nerves and/or blood vessels, although the underlying causes of these compressions can vary. A common area in which nerves are compressed is between the area of shoulder and neck known as the brachial plexus. This is known called "neurogenic thoracic outlet syndrome." Cases in which veins or arteries are compressed are known as vascular thoracic outlet syndrome and arterial thoracic outlet syndrome, respectively. Arterial TOS is the least common. People can experience one type of thoracic outlet syndrome or a combination of two types.

Compression associated with TOS may be the result of an extra rib (known as a cervical rib), hypertrophic (enlarged) muscle or scar tissue, or abnormality of muscles in the neck. It can also occur from a narrowing of the thoracic outlet space between the clavicle and chest wall or in the region where the nerves and blood vessels pass under muscles as they cross the shoulder. In rare cases, a prior displaced fracture of the clavicle (collarbone) can lead to brachial plexus-related TOS.

Hypermobility (looseness) of the either of the scapula (shoulder blade) or the glenohumeral joint of the shoulder can also create tension or traction on the nerves or blood vessels in the thoracic outlet region. Body position (such as poor posture or certain overhead activities) can also play a role in causing or contributing to symptoms.

What are the signs and symptoms of thoracic outlet syndrome?

Thoracic outlet syndrome symptoms vary widely depending on the type of TOS and its underlying cause. The classic, most common symptoms are pain, numb spots and/or tingling that radiate below the shoulder down towards the hand and usually into the pinky and ring finger. If compression involves the vascular structures, you may even see skin discoloration (paleness, bluishness, or even redness due to issues with blood circulation) in addition to a cold sensation in the chest, arm, shoulder, or side of the body.

If compression involves the nerves (brachial plexus), you may experience symptoms of a brachial plexopathy. This can include numbness, weakness (usually in the hand muscles), muscle wasting and muscle atrophy. You may also experience a loss of dexterity and fine motor skills. Many of the symptoms are similar to that of cervical radiculopathy, and these two conditions may be mistaken for one another. In rare cases, a person may have both conditions, with nerves pinched in two locations, causing what doctors call a "double crush" syndrome. An accurate diagnosis is paramount in order to receive the right treatment.

How is thoracic outlet syndrome diagnosed?

A diagnosis of TOS is based largely on the clinical symptoms a patient experiences and the physical exam by a doctor. Imaging tests – such as X-rays, MRIs, MRAs (magnetic resonance angiograms), MRVs (magnetic resonance venograms), MRNs (magnetic resonance neurograms) – and electrodiagnostic tests may help your doctor make the diagnosis, but they should be used only as adjuncts to the clinical assessment. In other words, your doctor should order such tests only to help confirm the suspected diagnosis or, in some cases, to objectively assess the functioning of your veins, arteries or nerves.

Making a diagnosis can sometimes be fairly straightforward, but more often it is difficult and elusive. This is because symptoms and their severity can vary widely. There is also some controversy within the field of medicine regarding the diagnosis and treatment of this condition, particularly around vascular TOS.

Neurogenic thoracic outlet syndrome (TOS involving the neurological structures) leads to weakness and muscle atrophy, in addition to pain. In this condition, there are usually neurological deficits that can be objectively identified by your doctor with the use of specialized electrodiagnostic tests called electromyography (EMG) and/or magnetic resonance neurography. A diagnosis for this condition is usually confirmed when an EMG test objectively demonstrates a patient's neurological deficits. Vascular thoracic outlet syndrome is more difficult to diagnosis objectively. The third category of TOS is very difficult to diagnose. Patients may experience vascular or neurological symptoms electrodiagnostic and imaging tests return normal results.

What kind of doctor treats thoracic outlet syndrome?

Appropriate treatment may span a wide variety of specialties, depending on symptoms and which systems in a person’s body are being affected. Physiatrists, neurologists, and pain management doctors are the most common types of physicians who treat thoracic outlet syndrome. Surgical treatment may be performed by a sports medicine orthopedic surgeon and/or vascular or thoracic surgeon.

How is thoracic outlet syndrome treated?

The treatment of thoracic outlet syndrome is usually nonsurgical and is directed at treating the underlying causes and contributing factors. Chiefly, this involves activity and posture modification and special exercises under the guidance of a physical therapist.

• Making changes to your posture, such as by postural exercises and ergonomic modifications may help significantly. The exercises usually focus on:
  • Stretching the pectorals or "pecs" (the muscles of the frontal chest wall)
  • Strengthening the shoulder retractors (rhomboids and trapezius muscles)
  • Improving head and neck alignment.
• Chin tucks and corner/doorway stretches are also recommended. These are performed by placing the forearm (wrist to elbow) upward on both sides of a doorway (or, when facing a corner, on both sides of the wall). You then lean forward until a stretch is felt in the front of the shoulder joint. This position can be held anywhere from 20 to 30 seconds. Any exercise that causes pain or triggers off neurological or vascular symptoms should be discontinued.
• Weight loss in overweight patients is helpful to alleviate compression.
• Oral medication such as anti-inflammatories (aspirin, ibuprofen, naproxen) may provide some relief, but addressing mechanical symptoms with the right stretching, strengthening and modifications of activities listed above is usually a better first-line approach.

What is the surgery for thoracic outlet syndrome?

Surgery should be considered only after conservative measures have been tried but without relieving symptoms or when there is a risk for loss of neurological or vascular function. Possible surgeries include:

• Removal of taut bands or scar tissue
• Splitting of or removal of abnormal muscles
• Removal of a cervical rib or a first thoracic rib
• Surgical stabilization of an unstable shoulder

Some of these procedures have greater risks than others, you and your doctor should carefully assess and weigh the risks against the potential benefits. Surgical decisions should be made not only when conservative care has been ineffective but also after considering how reliable surgery is in correcting or restoring proper anatomy in the least invasive way.

Key takeaways

• Thoracic outlet syndrome results from compression of nerves and/or blood vessels in the space between the neck and shoulder, leading to pain, numbness, tingling, weakness, or circulation changes in the arm and hand.
• There are three types of TOS: neurogenic (most common and objectively diagnosable), vascular (less common and sometimes disputed), and a mixed/unspecified type where test results are often normal.
• TOS causes include extra ribs, enlarged muscles, scar tissue, prior fractures, poor posture, overhead activity, or joint hypermobility that narrow the thoracic outlet.
• Diagnosis can be challenging and is based primarily on symptoms and physical exam, with tests like EMG, MRI, and vascular imaging used to confirm findings or rule out other causes.
• First-line treatment is nonsurgical, focusing on posture improvement, stretching tight chest muscles, strengthening upper back muscles, and modifying activities; weight loss and anti-inflammatories may also help.
• Surgery is considered only if conservative care fails or there is significant neurological or vascular risk, with procedures aimed at removing structural causes of compression.
• Care for TOS may involve multiple specialists, including physiatrists, neurologists, orthopedic surgeons, and vascular or thoracic surgeons.

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