What causes thoracic outlet syndrome (TOS)?

Dr. Joshua I. Greenberg, MD
Vascular Surgeon

The following are some causes of thoracic outlet syndrome (TOS):

  • skeletal abnormalities
    • cervical rib (extra rib)
    • elongated C7 transverse process (extra length in spine at the C7 vertebrae)
    • exostosis (abnormal bone growth) or tumor of the first rib or clavicle
  • soft-tissue abnormalities, abnormal muscle and tendon insertions
  • acute neck trauma (hyperextension neck injury, falls)
  • repetitive stress and posture (typing, assembly lines, overhead athletes)
Dr. Akash Bajaj, MD

Thoracic outlet syndrome (TOC) is a widely used term that encompasses three related syndromes that involve compression of the nerves, arteries and veins in the lower neck and upper chest area and cause pain in the arm, shoulder and neck. Most doctors agree that TOS is caused by compression of the brachial plexus or subclavian vessels as they pass through narrow passageways leading from the base of the neck to the armpit and arm.

Making the diagnosis of TOS even more difficult is that a number of disorders feature symptoms similar to those of TOS, including rotator cuff injuries, cervical disc disorders, fibromyalgia, multiple sclerosis, complex regional pain syndrome and tumors of the syrinx or spinal cord. The disorder can sometimes be diagnosed in a physical exam by tenderness in the supraclavicular area, weakness and/or a "pins and needles" feeling when elevating the hands, weakness in the fifth ("little") finger, and paleness in the palm of one or both hands when the individual raises them above the shoulders, with the fingers pointing to the ceiling. Symptoms of TOS vary depending on the type.

There are many causes of TOS, including physical trauma, anatomical defects, tumors that press on nerves, poor posture that causes nerve compression, pregnancy and repetitive arm and shoulder movements and activity, such as from playing certain sports.

There are many possible causes of thoracic outlet syndrome, a disorder in which the nerves and blood vessels between the neck and chest become compressed. In rare cases, an extra rib in the cervical spine, a congenital defect, is the cause. Thoracic outlet syndrome can also be caused by occupation-and sports-related repetitive motion injuries or trauma sustained from an accident. Other causes include poor posture, loosening of joints in pregnancy and tumors.

Congenital abnormalities are risk factors for some with thoracic outlet syndrome.

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