Thoracic Outlet Syndrome

Thoracic outlet syndrome (TOS) occurs when there’s compression of nerves or blood vessels in your lower neck and upper chest. Symptoms include pain, tingling and numbness in your arms and hands. Common causes include vigorous arm movements (especially in sports), traumatic injuries and anatomical variations you’re born with.


Location of the thoracic outlet and the structures that can become compressed.
Thoracic outlet syndrome happens when bones or muscles in your upper chest press on nerves or blood vessels. This compression leads to symptoms like pain in your neck, chest and arm.

What is thoracic outlet syndrome?

Thoracic outlet syndrome (TOS) is a group of disorders that happen due to compression of nerves or blood vessels in your lower neck and upper chest. “Thoracic outlet” is an anatomical term that refers to the opening between your neck and chest. This opening (also called your thoracic inlet or superior thoracic aperture) is a passageway for many important structures. These include your brachial plexus (nerves that cross from your neck to your armpit), subclavian artery and subclavian vein.

Normally, your thoracic outlet is wide enough to allow these nerves and blood vessels to pass through easily. But certain anatomical variations and injuries can disrupt this passageway and make it too narrow. When that happens, other structures in your chest (like bones or muscles) press on the nerves or blood vessels within this space. This compression can cause pain, abnormal sensations (paresthesia) and other symptoms in your upper body. The wide range of symptoms, which could point to many possible problems, can challenge and delay diagnosis.

Conservative treatments like physical therapy and pain medications help most people. But you may need surgery if those methods don’t work or if TOS interferes with normal blood flow.

Types of thoracic outlet syndrome

Healthcare providers classify TOS according to what’s compressed:

  • Neurogenic thoracic outlet syndrome: This is compression of nerves. Neurogenic TOS happens when there’s pressure on your brachial plexus, or the network of intertwined nerves that travel across your upper chest. This is by far the most common type. It represents about 95% of all cases of thoracic outlet syndrome. Most people receive a diagnosis in their 30s. The most common causes are repetitive stress injuries (often from sports) and sudden trauma to your neck (like whiplash).
  • Venous thoracic outlet syndrome: This is compression of your subclavian vein. Venous TOS is more common among men and people assigned male at birth (AMAB), typically in their 20s or 30s. A person usually feels symptoms in their dominant arm.
  • Arterial thoracic outlet syndrome: This is compression of your subclavian artery. It’s the rarest type of TOS, representing about 1% of all cases. However, among people younger than 40, arterial TOS is the most common cause of acute blood clots in the arm. Arterial TOS usually happens due to differences in anatomy that you’re born with (like a cervical rib). This type of TOS is more common among women and people assigned female at birth. This may be because up to 70% of cervical ribs occur in women.

The term “vascular thoracic outlet syndrome” refers to the venous or arterial types. These types usually require surgery to relieve symptoms and lower the risk of complications. Neurogenic TOS often responds well to physical therapy and exercise, but some people need surgery.

How common is thoracic outlet syndrome?

Researchers estimate that each year:

  • Neurogenic TOS affects 1 in 40,000 people.
  • Venous TOS affects 1 in 125,000 people.

The actual number of people who have this condition is likely higher than these numbers reflect because of challenges with diagnosis.


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Symptoms and Causes

What are the symptoms?

Thoracic outlet syndrome symptoms affect your upper body (neck, upper chest, shoulder, arm or hand), typically on one side. You may have:

  • Pain, which may worsen when you lift your arms.
  • Tingling or “pins and needles.”
  • Numbness.
  • Weakness.
  • Swelling or heaviness.
  • Skin color changes (skin that looks pale or blue).
  • Skin that feels cool to the touch.
  • Slow-healing sores on your fingers.

The specific symptoms you feel can vary depending on the type of TOS you have. That’s because symptoms result from compression of specific structures (nerves or blood vessels). This compression prevents those structures from doing their normal job. Here’s a breakdown:

  • Your brachial plexus gives movement and feeling to your arm and hand. Pain, tingling or numbness can occur when there’s pressure on your brachial plexus.
  • Your subclavian vein drains blood from your arm and sends it back toward your heart. So, pressure on this vein prevents blood from leaving your arm, leading to swelling and heaviness.
  • Your subclavian artery supplies oxygen-rich blood to your arm. Pressure on this artery reduces blood flow to your arm, hand and fingers. This poor circulation can cause numbness, tingling or pain, as well as skin that feels cool to the touch.

What does thoracic outlet pain feel like?

Thoracic outlet syndrome can cause pain in your neck, upper chest, shoulder and arm. This may feel like a dull ache, and it may worsen when you move your arms.

Some people confuse thoracic outlet syndrome pain with angina. Angina is chest pain you feel when your heart muscle doesn’t receive enough oxygen. But there are some important differences:

  • TOS pain doesn’t occur or get worse when you walk, while angina typically does. Angina also can have other associated symptoms like shortness of breath, heart palpitations and lightheadedness.
  • TOS pain usually gets worse when you raise the affected arm. This doesn’t happen with angina.
Thoracic outlet syndrome vs. heart attack or stroke

It’s important to keep in mind that TOS shares some symptoms with heart attack and stroke, which are medical emergencies. For example:

  • Chest pain, especially if it’s sudden or unexpected, can be a sign of a heart attack. But with a heart attack, you may have additional symptoms like shortness of breath, stomach discomfort, sweating and a feeling of impending doom.
  • Weakness on one side of your body can be a sign of a stroke. But with a stroke, you may have additional symptoms like slurred speech, drooping on one or both sides of your face and sudden vision loss.

Seek medical care right away if you have symptoms of a heart attack or stroke. These are medical emergencies that need immediate attention. Delaying care for a heart attack or stroke can be fatal.

What causes thoracic outlet syndrome?

Healthcare providers divide the causes of TOS into three main groups:

  • Congenital: These are variations in your anatomy that you’re born with. For example, you may be born with a cervical rib. This is an extra rib near (or sometimes fused to) your first rib. Or there may be abnormalities in your ribs, neck muscles or nearby ligaments. These variations may put pressure on the nerves or blood vessels in your thoracic outlet.
  • Traumatic: These are sudden injuries that affect your neck and upper chest area. Common examples are injuries from car accidents, like whiplash.
  • Functional: These are actions you do over and over that irritate or injure the structures in your thoracic outlet. Vigorous arm movements are a common culprit among athletes (especially baseball players and swimmers). Repeated overhead lifting, required in some lines of work, is another example.

Congenital factors predispose some people to TOS, but they may not feel any symptoms until there’s trauma to their neck from a sudden injury or chronic overuse.

What are the risk factors?

You may face a higher risk of developing thoracic outlet syndrome if you:

  • Play sports that involve repetitive arm or shoulder movement. Examples include baseball, swimming, golf and volleyball.
  • Engage in weightlifting.
  • Regularly carry heavy shoulder loads or lift things over your head.
  • Have an injury to your neck or back, such as whiplash.
  • Have tumors or large lymph nodes in your upper chest or armpit.
  • Have poor posture.


Is thoracic outlet syndrome serious?

Without treatment, thoracic outlet syndrome can lead to serious complications, including:

Diagnosis and Tests

How is thoracic outlet syndrome diagnosed?

Healthcare providers diagnose TOS by performing a physical exam and reviewing your medical history. As part of your physical exam, your provider may ask you to do movement-based tests, including:

  • Upper limb tension test.
  • Elevated arm stress test.

For these tests, your provider asks you to perform simple movements like lifting your arms, tilting your head and clenching your fists. They’ll see which movements trigger pain or other symptoms. The results can help with diagnosis.

Providers order lab and imaging tests as needed to confirm TOS and rule out other causes of your symptoms.

What tests will be done to diagnose thoracic outlet syndrome?

You may need one or more of the following tests:

These tests help your provider:

  • Look for anatomical variants (like a cervical rib).
  • Evaluate blood flow through your arteries and veins.
  • Rule out other conditions that cause similar symptoms.
  • Check the function of your muscles and nerves.
  • Find the exact location of compression.


Management and Treatment

How is thoracic outlet syndrome treated?

Thoracic outlet syndrome treatments vary, depending on the type of TOS you have and your symptoms. The goals of treatment are to reduce symptoms and prevent complications. Your provider will recommend the treatment option that’s right for you.

Possible treatments include:

  • Physical therapy: This is the most common initial treatment for neurogenic TOS. A physical therapist helps you increase your range of motion (how far you can move) in your neck and shoulders. Physical therapy also strengthens your muscles and promotes better posture. Most people with neurogenic TOS see an improvement in symptoms.
  • Medications to relieve pain: Your provider may recommend over-the-counter pain relievers, such as NSAIDs.
  • Medications to prevent or break up blood clots: Thrombolytic therapy helps people with arterial or venous TOS. You receive medication through an IV line or catheter that dissolves existing blood clots and prevent new ones from forming. Your provider may also prescribe anticoagulant medication.
  • Surgery: Most people with arterial or venous TOS need surgery. Some people with neurogenic TOS need surgery if other treatments don’t resolve symptoms. Surgeons use different methods depending on the type of TOS and your anatomy. For example, decompression surgery removes abnormal bone or tissue that’s causing compression. Other surgeries repair structural problems with your blood vessels to improve blood flow. Your provider will tell you if you need surgery and what it involves. They’ll also explain any possible risks.

Can thoracic outlet syndrome go away on its own?

Don’t wait for your symptoms to go away. Seek medical care if you have symptoms of TOS. While in many cases, conservative measures like physical therapy alleviate symptoms, some people need surgery or other treatments to prevent serious complications. Your provider will tell you the treatment plan that’s appropriate for your needs.


Can I prevent thoracic outlet syndrome?

You can’t always prevent TOS. Many of the causes are beyond your control. But there are some things you can do to lower your risk:

  • If you play a sport that involves repetitive arm motions, talk to your coach or trainer about exercises to strengthen the muscles around your shoulder.
  • If your job requires heavy lifting or overhead arm movements, talk to a healthcare provider about exercises that can help lower your risk of injury.

Outlook / Prognosis

What can I expect if I have this condition?

The outlook for people with thoracic outlet syndrome varies based on the type. Your healthcare provider is the best person to ask about what you can expect going forward.

Living With

How do I take care of myself?

Follow your healthcare provider’s guidance on how to take care of yourself if you have TOS. Your provider may recommend you:

  • Avoid carrying heavy bags on your shoulder or lifting objects above your head.
  • Work with a physical therapist.
  • Do exercises at home to strengthen your muscles and improve your posture.
  • Modify your daily activities to limit or avoid certain movements that cause symptoms.

When should I see my healthcare provider?

Call your provider if you have new or changing symptoms. They’ll tell you how often you need to come in for follow-ups and tests.

What questions should I ask my doctor?

Here are some questions you can ask if you recently received a diagnosis of thoracic outlet syndrome:

  • What type of thoracic outlet syndrome do I have?
  • What’s the cause?
  • What treatments do you recommend, and what’s the timing for them?
  • How will we know if the treatments are successful?
  • What are the risks of treatment?
  • What changes should I make to my normal routine or activities?
  • How can I ease symptoms at home?
  • What’s my outlook?

A note from Cleveland Clinic

Thoracic outlet syndrome (TOS) can interfere with your usual routine. It may feel frustrating to take time away from your sport or slow down your pace at work. But be patient. Taking care of yourself with physical therapy or other treatments will help you regain your strength and feel much better in the long run. Talk to your provider if you have any questions or concerns about your condition, treatment plan or outlook.

Medically Reviewed

Last reviewed on 05/03/2023.

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