Causes of Thoracic Outlet Syndrome

Causes of Thoracic Outlet Syndrome

Multiple Causes of Thoracic Outlet Syndrome

While there are many causes of thoracic outlet syndrome, thoracic outlet syndrome specialists in the past have broadly classified TOS into one of three types. Each of these three types of thoracic outlet syndrome becomes defined by the primary structure that suffers from compression. We find it easier to learn about the causes of thoracic outlet syndrome by starting with this simplified model.

To clarify, three vital structures pass through the thoracic outlet on each side:

  • Brachial plexus
  • Subclavian Vein
  • Subclavian Artery
Causes of thoracic outlet syndrome-Brachial Plexus, Subclavian Vein, Subclavian Artery

In the classical model of thoracic outlet syndrome, compression or injury of one of these vital structures may occur, resulting in symptoms of one type of thoracic outlet syndrome.

Introduction to the Causes of Thoracic Outlet Syndrome

As an introduction the classical model of thoracic outlet syndrome, we find it helpful to review the basic causes of thoracic outlet syndrome for each type of thoracic outlet syndrome. Click through each section below to the next page once you are comfortable with the basics.

Causes of Neurogenic Thoracic Outlet Syndrome

Five nerve roots arise from the spinal cord on each side of the neck. Then, these nerve roots travel out of the spine to the thoracic outlet on each side. In each thoracic outlet, the roots form a complex branching network, called the brachial plexus. Compression of the brachial plexus or tension on the brachial plexus results in symptoms of neurogenic thoracic outlet syndrome. Given the complexity of the structure of the brachial plexus, patients can suffer a broad range of symptoms.

Thus, doctors typically see a complex clinical presentation, since compression may involve different parts of the brachial plexus. Symptoms include pain, numbness, tingling, coldness and weakness of the affected upper extremity.

Causes of Venous Thoracic Outlet Syndrome

A single, large subclavian vein drains almost all of the blood from each arm. Compression of this vein can cause impaired venous drainage of the arm. When compression is severe or prolonged, it can cause damage to the inner vein wall. As a result, blood clot can form within the vein. Signs and symptoms include swelling, heaviness and cyanosis (abnormal blue color) of the affected arm. Blood clots can break off and travel to the lungs or, rarely, to the brain, resulting in a stroke.

Causes of Arterial Thoracic Outlet Syndrome

A single, large subclavian artery provides most of the blood flow to each arm. Compression of this artery causes damage to the arterial wall. Damage to the inner wall can cause scar tissue and stenosis (narrowing of the artery). In contrast, damage to the full thickness of the wall can result in an aneurysm (focal ballooning of the artery). As a result of this aneurysm, a doctor may feel a pulsatile mass in the thoracic outlet. When arterial damage occurs, blood clots may form. These clots can break off and travel to distal arteries.  As a result, blood flow stops, and gangrene of the affected area may develop.

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Can Multiple Types of TOS Occur in the Same Patient?

Yes, one patient can have multiple types of TOS at the same time. As shown above, the artery, vein, and brachial plexus pass through each thoracic outlet together. Furthermore, the mechanism of compression is similar for all types of TOS. Thus, a patient can have compression of 1, 2, or all 3 of these vital structures. In fact, many patients with neurogenic TOS have significant compression of the subclavian vein, but without a blood clot. Since this compression impairs venous drainage of the arm, swelling or edema of the arm can result. As a result, compression of the brachial plexus is magnified. In that case, treatment to relieve the venous compression helps relieve compression on the brachial plexus.

It is often difficult for a physician to distinguish these multiple compression effects. Therefore, modern imaging quite often provides this important additional information prior to treatment.

Do you have pain, numbness, tingling or weakness? Click to learn more about the diagnosis of thoracic outlet syndrome.

Learn how the NeoVista® MRI for TOS provides diagnostic information that is not available elsewhere.

Best treatment of thoracic outlet syndrome requires a dedicated team of thoracic outlet syndrome specialists.