Thoracic outlet syndrome (TOS) causes pain in the shoulder, arm, and neck. It happens when the nerves or blood vessels just below your neck are compressed, or squeezed. The compression can happen between the muscles of your neck and shoulder or between the first rib and collarbone. You may feel burning, tingling, and numbness along your arm, hand, and fingers. If a nerve is compressed, you may also feel weakness in your hand. If a vein is compressed, your hand might be sensitive to cold, or turn pale or bluish. Your arm might swell and tire easily.

TOS is more common in women. It usually starts between 20 and 50 years of age. Doctors do nerve and imaging studies to diagnose it.

There are many causes of TOS, including

• Injury
• Anatomical defects
• Tumors that press on nerves
• Poor posture that causes nerve compression
• Pregnancy
• Repetitive arm and shoulder movements and activity, such as from playing certain sports

Treatment depends on what caused your TOS. Medicines, physical therapy, and relaxation might help. Surgery may also be an option. Most people recover.

Thoracic outlet syndromes (TOSs) are a group of disorders with one common feature: the compression of 1 or more of the nerves and/or blood vessels just above the first rib and behind the collarbone. There are 4 recognized subtypes of TOS, each with a distinct cause and pattern of symptoms. A fifth subtype is controversial. While thoracic outlet syndromes as a group are not rare, individual subtypes of TOS are considered rare.

The subtypes include:

• Arterial TOS (A-TOS) - due to compression of the subclavian artery, most commonly caused by a cervical rib. Symptoms may include blood clots, arm pain with exertion, or acute arterial thrombosis (sudden blood flow obstruction in an artery).
• Venous TOS (V-TOS) - due to compression of the subclavian vein, often associated with repetitive arm activities. It may cause pain, swelling, and deep vein thrombosis.
• Traumatic neurovascular TOS - occurs after trauma to the collarbone and may affect both nerves and vessels. Symptoms may include pain, swelling, bruising, weakness, and loss of sensation in the arm and hand.
• True neurogenic TOS (TN-TOS) - caused by compression of the brachial plexus. Symptoms include numbness, abnormal sensations, and weakness of the arms and shoulders, as well as pain in the neck, shoulder or hand.
• Disputed TOS - the vast majority of neurogenic cases. It is controversial whether it is a true form of TOS because it lacks a consistent physical abnormality, a recognized cause, consistent symptoms, a reliable method of testing, and a standard treatment. Pain and tingling or numbness in the neck, arm and hand are common complaints.

Treatment for TOS depends on the type and whether symptoms are present. Treatment may involve physical therapy, oral or injected medication (e.g. pain medicine or steroids), thoracic outlet decompression surgery, and/or thrombolytic therapy.

Cervical ribs are actually thought to be a common trait. It has been estimated that 1 to 2% of the population have a cervical rib. Cervical ribs can affect one or both sides of the neck, and may cause thoracic outlet syndrome by putting pressure on an artery.

Currently, the cause of cervical ribs is not known. In general, both genetic and environmental factors are thought to be involved. There have been animal studies investigating the role of HOX genes in causing extra ribs. Studies have also suggested environmental exposures, such as maternal exposure to foreign chemicals or stress during pregnancy could play a role. Further research in this area is needed. There have been rare case reports of families with multiple members with cervical rib. In these families autosomal dominant inheritance was suspected.

Making the diagnosis of a thoracic outlet syndrome (TOS) can be hard because several disorders cause similar signs and symptoms. These may include rotator cuff injuries, cervical disc disorders, fibromyalgia, multiple sclerosis, complex regional pain syndrome, and tumors of the syrinx or spinal cord. TOS can sometimes be diagnosed based on a physical exam and specific symptoms present, but tests and imaging studies are often used to rule out other conditions.

Further testing to rule out other conditions or confirm a suspected diagnosis of TOS may include:

• Imaging studies such as chest X-ray, ultrasound, CT scan, MRI, arteriography, or venography
• Electrodiagnostic testing or brachial plexus (interscalene) block for suspected neurogenic TOS
• Vascular studies for suspected arterial TOS

Determining the exact incidence of thoracic outlet syndromes (TOSs) is difficult because symptoms vary greatly and there is no specific test that confirms the diagnosis. Estimates of the incidence of TOSs range from 3 to 80 cases per 1000 people.

While thoracic outlets syndromes as a group are not rare, individual subtypes of TOS are considered rare.

What is Thoracic Outlet Syndrome?

TOS is an umbrella 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, but there is considerable disagreement about its diagnosis and treatment.
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.

• Neurogenic TOS has a characteristic sign, called the Gilliatt-Sumner hand, in which there is severe wasting in the fleshy base of the thumb. Other symptoms include paresthesias (pins and needles sensation or numbness) in the fingers and hand, change in hand color, hand coldness, or dull aching pain in the neck, shoulder, and armpit.
• Venous TOS features pallor, a weak or absent pulse in the affected arm, which also may be cool to the touch and appear paler than the unaffected arm. Symptoms may include numbness, tingling, aching, swelling of the extremity and fingers, and weakness of the neck or arm.
• Arterial TOS most prominently features change in color and cold sensitivity in the hands and fingers, swelling, heaviness, paresthesias and poor blood circulation in the arms, hands, and fingers.

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.
TOS is more common in women. The onset of symptoms usually occurs between 20 and 50 years of age. Doctors usually recommend nerve conduction studies, electromyography, or imaging studies to confirm or rule out a diagnosis of TOS.

Is there any treatment?

Treatment begins with exercise programs and physical therapy to strengthen chest muscles, restore normal posture, and relieve compression by increasing the space of the area the nerve passes through. Doctors will often prescribe non-steroidal anti-inflammatory drugs (such as naproxen or ibuprofen) for pain. Other medicines include thromobolytics to break up blood clots and anticoagulants to prevent clots. If this doesn't relieve pain, a doctor may recommend thoracic outlet decompression surgery to release or remove the structures causing compression of the nerve or artery.

What is the prognosis?

The outcome for individuals with TOS varies according to type. The majority of individuals with TOS will improve with exercise and physical therapy. Vascular TOS, and true neurogenic TOS often require surgery to relieve pressure on the affected vessel or nerve.