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What is TOS?

What is the thoracic outlet?

The thoracic outlet is an area of the body where structures such as certain arteries, veins, and nerves must travel through to get from the center of the body (where the heart and spine are) to the arms.  Each side of the body has a thoracic outlet.  The thoracic outlet spans from the lower neck just above the collarbone through the upper chest to the shoulder just above the armpit. (See the red shaded area in the photo.)

What is thoracic outlet syndrome?

Thoracic Outlet Area shaded in red

thoracic outlet area shaded in red above

Thoracic outlet syndrome (TOS) is a group of rare conditions that involves compression of the nerves or blood vessels that pass through the thoracic outlet.  There are 3 types of TOS. Compression of the nerves that pass through the thoracic outlet is known as Neurogenic TOS (NTOS) and can lead to disabling pain in the neck, shoulder, and upper back as well as pain, numbness, tingling, and weakness among other symptoms in the arm and hand.  Compression of the vein is known as Venous TOS (VTOS) and can lead to blood clots also known as deep vein thrombosis or DVT.  Compression of the artery is known as Arterial TOS (ATOS) and can lead to blood clots or an aneurysm.  Both Venous TOS and Arterial TOS affect the ability to circulate blood through the arm.  The most common type of TOS is neurogenic which accounts for around 95% of TOS cases.  Venous TOS is the second most common type accounting for around 3-4% of TOS cases.  Arterial TOS is the least common type of TOS accounting for around 1-2% of TOS cases.

What is pec minor syndrome?

Neurogenic Pec Minor Syndrome (NPMS) often accompanies NTOS.  It occurs when the same group of nerves that are compressed by NTOS get compressed by the pec minor muscle as they approach the armpit.  It can cause symptoms similar to those of NTOS.  Occasionally, the pec minor muscle can compress the vein resulting in venous pec minor syndrome.  While it is anatomically possible for the pec minor muscle to compress the artery, it has not been reported.

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