Thoracic Outlet Syndrome (TOS) occurs when the nerves and blood vessels between the base of the neck and armpit or brachial plexus are compressed. If the shoulder muscles in the chest are not strong enough to hold the collarbone in place, it can slip down and forward, putting pressure on the nerves and blood vessels and reducing blood flow to the hands.

This can result from:

  • Congenital abnormalities of muscles and ligaments attached to the first rib, or an extra rib
  • Traumatic injuries to the neck, such as whiplash
  • Injuries of the arm, such as overstretching
  • Repetitive activities (assembly line, keyboard typing, etc.)

There are three types of TOS: neurogenic (NTOS), venous (VTOS) and arterial (ATOS). Thoracic outlet syndrome most commonly affects the nerves, but the condition can also affect the veins and arteries. In all types of TOS, the thoracic outlet space (space between the collar bone or clavicle, and the first rib) is narrowed, and scars, of varying degrees and sizes, can form around these structures. TOS can occur on one or both sides of the body.

Who Does Thoracic Outlet Syndrome Affect

Thoracic outlet syndrome affects people of all ages and genders. Neurogenic TOS is the most common form of the disorder (95 percent of people with TOS have this form of the disorder) and generally affects middle-aged women. Recent studies have shown that, in general, TOS is more common in women than men, particularly among those with poor muscular development, poor posture or both.

Causes of Thoracic Outlet Syndrome

TOS is caused by the compression of blood vessels and/or nerves in the tight passageway of the thoracic outlet (space between the base of the neck and the axilla or armpit).  It is known that when these structures are abnormally compressed, they become irritated and can cause TOS. Thoracic outlet syndrome can be a result of an extra first rib (cervical rib), an accessory (extra) muscle, or scar tissue from trauma or a fracture of the clavicle (collarbone) that reduces the space for the vessels and nerves.

These factors may increase your chances of developing thoracic outlet syndrome:

  • Congenital abnormalities or birth defects, resulting is bony and soft tissue abnormalities
  • Repetitive activities that can result in injuries from overuse (i.e. assembly line work, keyboard typing, overhead reaching, carrying heavy shoulder loads, etc.)
  • Injury to the neck or back (i.e. whiplash injury or overstretching)
  • Sleep disorders
  • Tumors or large lymph nodes in the upper chest or underarm area
  • Stress or depression
  • Participating in sports that involve repetitive arm or shoulder movement, such as baseball, swimming, golfing and volleyball
  • Poor posture
  • Weightlifting
  • Motor vehicle crashes


Thoracic outlet syndrome is a difficult condition to diagnose and treat. Because it shares many of the same symptoms as other upper extremity conditions, such as carpal tunnel syndrome, it is sometimes misdiagnosed. Signs and symptoms of TOS help determine the type or types of disorder a patient has. Thoracic outlet syndrome disorders differ, depending on the part(s) of the body they affect.

The most common symptoms of TOS are:

  • Numbness and tingling of the fingers or in the arm
  • Pain in the shoulders, neck, and arms
  • Impaired circulation to the affected areas
  • Muscle spasms in the scapular area or upper back - the area between the base of the neck and the shoulders
  • Chest pain, frequently mimicking a heart condition, that does not go away with rest, and is often relieved with the elevation of the arm
  • Headaches
  • Wasting in the fleshy base of your thumb (Gilliatt-Sumner hand)
  • Weakness of the arm and hand with weakening of hand grip on the affected side
  • Symptoms become worse with repetitive or overhead activities.

Patients can also experience symptoms based on the type of TOS they have developed, as seen below:

  • Arterial thoracic outlet syndrome (ATOS): The least common, but most serious, type of TOS is caused by congenital (present at birth) bony abnormalities in the lower neck and upper chest. Symptoms include cold sensitivity in the hands and fingers, numbness, pain or sores of the fingers and poor blood circulation to the arms, hands and fingers.
  • Neurogenic thoracic outlet syndrome (NTOS): This condition is related to abnormalities of bony and soft tissue in the lower neck region (which may include the cervical rib area) that compress and irritate the nerves of the brachial plexus, the collection of nerves that supply motor (movement) and sensory (feeling) function to the arm and hand. Symptoms include weakness or numbness of the hand, decreased size of hand muscles which usually occurs on one side of the body, pain, tingling, prickling, numbness and weakness of the neck, chest, and arms.
  • Venous thoracic outlet syndrome (VTOS): This condition is caused by damage to the major veins in the lower neck and upper chest. The condition develops suddenly, often after unusual and tiring exercise of the arms. Symptoms include swelling of the hands, fingers and arms, as well as heaviness and weakness of the neck and arms. The veins in the anterior (front) chest wall veins also may appear dilated (swollen).

Diagnosis and Treatments

TOS can be difficult to diagnose and treat. At MedStar Good Samaritan, our approach is to recommend a combination of physical therapy, medication, and when appropriate, weight loss, as a first line of defense before surgery. For patients who do not find relief from this approach, surgery may be the answer. Patients who receive surgery usually have excellent results.  

The first, and most important step, though, is getting a good diagnosis. Common diagnostic tests and procedures can include:

  • Nerve conduction studies to evaluate the function of the motor and sensory nerves
  • Vascular studies of the arteries or veins
  • Chest X-ray to rule out cervical rib abnormalities
  • Cervical spine X-rays to rule out a cervical rib (extra rib) or cervical spine (neck) abnormalities
  • Computed tomography (CT) scan and magnetic resonance imaging (MRI) of the chest
  • CT scan or MRI of the spine to rule out cervical spine impingement or pressure, which can mimic neurogenic thoracic outlet syndrome
  • Magnetic resonance imaging with angiography (MRA) to view blood vessels
  • Arteriogram/venogram, X-ray that uses dye to look at blood flow)
  • Blood tests

Talk to your doctor to learn what tests may be necessary to help determine your diagnosis, as well as next steps to treat your condition.  Based on the results, he or she can work with you to determine the best course of treatment to help improve your quality of life.