Thoracic outlet syndrome (TOS)

The thoracic outlet is an area in the upper chest, between the ribcage and clavicle (collarbone). In this area, a group of blood vessels and nerves called the brachial plexus sends messages between your brain and your hand and arm.

Thoracic outlet syndrome (TOS) describes several uncommon conditions that compress the brachial plexus. There are three types of thoracic outlet syndrome:

• Arterial TOS: People with arterial TOS have an extra rib above the highest rib, closest to the neck. This extra rib compresses the subclavian artery, the blood vessel that carries blood behind the collarbone to your arm and hand. It can cause pain and numbness in the hand due to blood clots. Some people form a dangerous aneurysm, a balloon-like bulge in the artery.
• Neurogenic TOS: The most common type of TOS, neurogenic refers to nerves. Tears in the scalene muscles on the sides of the neck cause muscle spasms that can irritate the nerves in the brachial plexus.
• Venous TOS: This type of TOS affects the subclavian vein, which runs between the collarbone and first rib. Athletes who frequently lift or throw a ball overhead can develop injuries in the vein. Clots and blockages can result.

Thoracic outlet syndrome usually affects young, active people. Neurogenic TOS more often affects women, while arterial TOS and venous TOS affect people of all genders.

Symptoms of thoracic outlet syndrome include:

• Cold feeling or other signs of poor circulation in the forearm or hand
• Neck and shoulder pain or tingling
• Sores on the fingers that don’t heal well
• Swelling in the affected arm
• Tingling or numbness in the fingers (especially the pinky and ring fingers) or inner forearm
• Weak grip in the hand muscles

Most often, thoracic outlet syndrome develops from a combination of the way your body is built and frequent motions of the area. The thoracic outlet is a narrow space, where compression can easily occur. Sometimes, the space is too narrow for nerves and blood vessels to travel smoothly through this space between the upper ribs and collarbone.

Other causes of pressure that leads to thoracic outlet syndrome may include having:

• An extra rib above the first rib
• A change in the first rib
• An unusually tight band of fibrous muscle connecting your ribs and spine
• Past injuries to the brachial plexus
• Shoulder overuse, especially in overhead activities like lifting or throwing
• Long necks and sloped shoulders, which can put extra pressure on the area