Thoracic Outlet Syndrome

What is Thoracic Outlet Syndrome?

The thoracic outlet is located just below the collarbone. Here, you will find the blood vessels that carry blood and oxygen to the arms and hands. Thoracic outlet syndrome, also known as TOS, occurs when you experience symptoms in your arms and hands as a result of increased pressure on the blood vessels or nerves in the thoracic outlet.

Types of thoracic outlet syndrome

There are three different types of thoracic outlet syndrome, including:

• Neurogenic TOS: this occurs when the nerves in the thoracic outlet are compressed: this is by far the most common type of TOS, accounting for around 95% of cases.
• Venous TOS: this form of TOS is associated with pressure or obstruction in the subclavian vein, the main vein that supplies the arm. This form of TOS accounts for 4% of cases.
• Arterial TOS: this rare form of TOS affects just 1% of cases. It occurs when the main artery serving the arm, the subclavian artery, is damaged or diseased. Almost all cases are linked to an extra or abnormal rib.

What causes thoracic outlet syndrome?

The cause often depends on the type of thoracic outlet syndrome.

Neurogenic TOS is most commonly caused by traumatic injuries such as whiplash, falls and slips. Repetitive stress syndrome may also cause neurogenic TOS.

Venous TOS most commonly results from overuse of the arm and shoulder. It may also be linked to congenital narrowing of the space available around the vein, which results in compression.

Arterial TOS is most commonly linked to congenital abnormalities affecting the rib, such as an extra cervical rib or an abnormal first rib. These abnormalities cause the subclavian artery to become narrower. This can result in the development of an aneurysm and a clot within the aneurysm or within the artery. Blood clots are dangerous because pieces of the clot can break away and travel through the bloodstream, potentially preventing sensation and feeling in the hands. In this case, when circulation to the hand is obstructed, immediate treatment is essential. The aim of treatment is to restore circulation.

How is thoracic outlet syndrome diagnosed?

It can be difficult to diagnose thoracic outlet syndrome and a variety of tests will be used in addition to a physical examination and taking note of medical history and symptoms.

Tests that commonly used include:

• Pulse volume recordings
• X-rays
• Nerve conduction velocity test
• CT and/or MRI scan
• Venography
• Arteriography
• Doppler ultrasound

The results of the tests will be used to confirm a diagnosis and determine the type of thoracic outlet syndrome.

What are the symptoms?

The symptoms depend on the type of TOS and include:

In neurogenic TOS: numbness, pain, a tingling sensation and a feeling of weakness and tiredness in the hand and arm, which gets worse when the arm is raised over the head. Additional symptoms include headaches and pain in the neck and shoulder. Shoulder pain tends to radiate down the arm.

In venous TOS: venous TOS causes significant swelling and discolouration in the entire arm in addition to pain.

In Arterial TOS: arterial TOS is characterised by pain, paleness in the hands and cold hands. Using the arm can also result in cramp.

What are the treatment options?

Treatment options are decided based on the type of TOS and the severity of symptoms.

Neurogenic TOS: many patients undergo a course of physiotherapy in addition to exercises at home. Your doctor may also prescribe medication to relax the muscles and reduce swelling. Applying heat or ice packs can also help to ease discomfort. If these measures are ineffective and symptoms are hindering your day to day life, surgery may be recommended. Surgery involves either removing some muscle tissue or a rib, or both. It is generally only recommended when other treatments have been unsuccessful, as it carries risks.

Venous TOS: the aim of treatment is to dissolve the blood clot using clot-busting medication, anticoagulants or, less commonly, surgery. After the clot removal process, surgery to remove the first rib may be recommended to allow more space for the subclavian vein. If the vein is very narrow, a procedure known as an angioplasty may be performed. This involves using a balloon to widen the vein.

Arterial TOS: arterial TOS is treated through repairing or replacing the damaged artery. It may be possible to repair the artery, but if this is not viable, a graft may be used to create a replacement. It is also important to remove the rib contributing to increased pressure on the vein.