What is Thoracic Outlet Syndrome?

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By Dr. Stefanie Yao
Published on January 27, 2014

The thoracic outlet is the space between your collarbone (clavicle) and your first rib. This narrow passageway is crowded with blood vessels, muscles, and nerves which can place pressure on the nerves and blood vessels underneath, causing a variety of symptoms known as thoracic outlet syndrome (TOS).

The term thoracic outlet syndrome can be used to describe a collective syndrome in which there is compression of the neurovascular structures under the thoracic outlet space. The thoracic outlet space is bordered by the scalene muscles, first rib, and clavicle. The neurovascular structures, i.e. nerves and blood vessels, pass from the neck and thorax into the axilla and down to the arms and hands through this space.

Causes of Thoracic Outlet Syndrome:

Thoracic outlet syndrome can result from injury, disease, or a congenital anomaly. Some typical causes of thoracic outlet syndrome are an elongated C7 transverse process, cervical rib, hypertonic anterior neck muscles, congenital muscle developmental abnormalities, poor posture, clavicle or first rib fracture, certain repetitive occupational movements. Other rare causes of TOS include tumors and or head or neck trauma.

Within the classification of thoracic outlet syndrome there are three categories of Thoracic Outlet Syndrome: Neurogenic TOS, Arterial TOS,  and/or Venous TOS.

Arterial TOS:

Arterial TOS happens when the subclavian artery become compressed or entrapped within the within the thoracic outlet space leading to decreased blood flow to the arms and hands. Typical symptoms of arterial TOS include digital and hand ischemia – pain, paresthesia, coldness and color changes and in some cases there maybe shoulder or neck pain. Physical findings that may be present include loss or decrease in pulses at rest, color changes, and ischemic fingertips.

Venous TOS:

Venous TOS occurs when the subclavian vein become compressed or entrapped within the thoracic outlet space. This is also known as Paget-Schroetter syndrome. Symptoms of an obstructed subclavian vein include arm swelling, cyanosis, pain, and mild paresthesia in the arm and hands. Physical findings include swelling of the arm, forearm and or hand, discoloration, and visible subcutaneous veins over shoulder and chest wall.

Neurogenic TOS:

Neurogenic TOS is the most common form of thoracic outlet syndrome, occurring in about 95% of cases. It is due to the compression or entrapment of a component of the brachial plexus which supplies nerve function to the arm, forearm, and hands. Symptoms of neurogenic TOS, often due to nerve irritation, are pain, paresthesia, arm and hand weakness. Paresthesia tends to involve the 4th and 5th fingers and inside of the forearm. In addition, there may be associated neck pain and pain over the trapezius, anterior chest wall, and in some cases associated occipital headaches.

TOS Symptoms and Treatment:

The signs and symptoms of Thoracic Outlet Syndrome can mimic those of carpal tunnel syndrome, ulnar neuropathy, cervical radiculopathy, a brachial plexopathy, and even a myelopathy. Therefore it is important to rule out other differential diagnoses.

Symptoms may vary, depending on whether nerves or blood vessels are compressed. Symptoms from nerve compression are much more common than symptoms from blood vessel compression. Pressure on the brachial plexus nerves depends on the severity of the entrapment/compression. Symptoms may include aching pain in the neck, shoulder, arm or hand, to pain, numbness, and/or tingling on the inside of the forearm and the fourth and fifth fingers of the hand and even weakness. Pressure on the blood vessels often reduces blood flow to the arm, resulting in swelling and redness and can make your arm feel cool. With both types of compression of either nerve or vascular thoracic outlet syndrome, overhead activities may be difficult.

Most TOS patients tend to improve with exercise, stretches, lifestyle modifications, and physical and manual therapies. However, there are cases of Thoracic Outlet Syndrome where surgical intervention is required.


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