Thoracic Outlet Syndrome: Why Your Nerves Are Pinched + Medical Next Steps

Thoracic outlet syndrome (TOS) is a condition that happens when nerves or blood vessels are compressed (pinched) in a narrow space between your collarbone and first rib. This area is called the thoracic outlet. When structures in this space become irritated or squeezed, it can cause pain, numbness, weakness, and circulation problems in the arm and hand.

Thoracic outlet syndrome is real, medically recognized, and treatable—but it can be tricky to diagnose because its symptoms often overlap with other conditions like carpal tunnel syndrome or cervical spine problems.

Let's break down what's happening in your body, what symptoms to watch for, and what medical steps come next.

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What Is Thoracic Outlet Syndrome?

The thoracic outlet is the small passageway between:

• Your collarbone (clavicle)
• Your first rib
• Surrounding muscles (especially the scalene and pectoralis minor muscles)

Running through this tight space are:

• The brachial plexus (a bundle of nerves that control your arm and hand)
• The subclavian artery
• The subclavian vein

When any of these structures are compressed, you may develop thoracic outlet syndrome.

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The Three Types of Thoracic Outlet Syndrome

There are three main types of thoracic outlet syndrome. Understanding which type you have is key to treatment.

1. Neurogenic Thoracic Outlet Syndrome (Most Common)

This accounts for about 70–90% of cases.

It occurs when the brachial plexus nerves are compressed.

Common symptoms include:

• Numbness or tingling in the arm or fingers
• Hand weakness
• Aching in the neck, shoulder, or arm
• Symptoms that worsen when arms are raised
• Dropping objects due to reduced grip strength

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2. Venous Thoracic Outlet Syndrome

This happens when the subclavian vein is compressed.

Symptoms may include:

• Arm swelling
• Bluish discoloration of the arm
• A feeling of heaviness
• Visible enlarged veins in the shoulder or chest
• Sudden arm pain with swelling (possible blood clot)

Venous thoracic outlet syndrome can sometimes be serious and may require urgent medical care.

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3. Arterial Thoracic Outlet Syndrome (Rare but Serious)

This occurs when the subclavian artery is compressed.

Symptoms can include:

• Cold or pale fingers
• Weak or absent pulse in the arm
• Hand pain during activity
• Slow-healing sores on fingers

Arterial thoracic outlet syndrome is uncommon but potentially dangerous and requires prompt medical evaluation.

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Why Are Your Nerves Getting Pinched?

Thoracic outlet syndrome usually develops because the thoracic outlet space becomes too narrow. This narrowing may happen due to:

Structural Causes

• A cervical rib (an extra rib present from birth)
• An unusually tight fibrous band
• Previous collarbone fracture
• Bone abnormalities

Posture and Muscle Imbalance

• Rounded shoulders
• Forward head posture
• Slouching at a desk
• Repetitive overhead movements

Repetitive Motion or Overuse

• Athletes (especially swimmers, pitchers, weightlifters)
• Jobs involving lifting or overhead work

Trauma

• Car accidents (especially whiplash)
• Falls
• Shoulder injuries

Often, thoracic outlet syndrome is not caused by one single event but by a combination of anatomy and repetitive strain.

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How Thoracic Outlet Syndrome Is Diagnosed

There is no single test that confirms thoracic outlet syndrome. Diagnosis usually involves:

1. Medical History

Your doctor will ask about:

• Symptom patterns
• Activities that trigger symptoms
• Injury history
• Duration of symptoms

2. Physical Exam

The doctor may:

• Check your posture
• Assess muscle strength
• Evaluate sensation
• Perform arm positioning tests to reproduce symptoms

3. Imaging Tests

Depending on your symptoms, your doctor may order:

• X-rays (to check for a cervical rib)
• MRI (to look at soft tissue structures)
• Ultrasound
• CT angiography
• Nerve conduction studies

Imaging helps rule out other conditions and determine whether nerves, veins, or arteries are involved.

If you're experiencing unexplained arm pain, numbness, or weakness and want to understand whether these symptoms align with Thoracic Outlet Syndrome, a free AI-powered symptom checker can help you organize your concerns before your doctor's appointment.

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Treatment for Thoracic Outlet Syndrome

The good news: most people with neurogenic thoracic outlet syndrome improve without surgery.

First-Line Treatment: Physical Therapy

This is the cornerstone of treatment.

Therapy focuses on:

• Improving posture
• Strengthening shoulder stabilizing muscles
• Stretching tight neck and chest muscles
• Increasing range of motion
• Teaching ergonomic adjustments

Consistent physical therapy over several months often leads to significant improvement.

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Medications

Your doctor may recommend:

• Anti-inflammatory medications
• Muscle relaxants
• Nerve pain medications (in some cases)

These help manage symptoms but do not fix structural compression.

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Lifestyle Adjustments

Small changes can make a big difference:

• Adjust workstation ergonomics
• Avoid prolonged overhead activity
• Improve posture
• Take frequent movement breaks
• Modify athletic training

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Injections

In some cases, doctors may use:

• Botox injections into scalene muscles
• Local anesthetic injections

These can help confirm diagnosis and reduce muscle compression.

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Surgery (When Necessary)

Surgery is usually reserved for:

• Severe neurogenic thoracic outlet syndrome not improving after months of therapy
• Venous thoracic outlet syndrome with clots
• Arterial thoracic outlet syndrome
• Progressive muscle wasting or significant weakness

Surgical treatment typically involves removing part of the first rib or releasing tight muscles to relieve compression.

Most patients do well when surgery is carefully selected and performed by experienced specialists.

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When Thoracic Outlet Syndrome Is More Serious

Seek immediate medical care if you notice:

• Sudden arm swelling and pain
• Blue or pale arm
• Cold fingers with loss of pulse
• Chest pain or shortness of breath
• Sudden weakness

These may signal a blood clot or arterial compromise and require urgent evaluation.

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Conditions That Can Mimic Thoracic Outlet Syndrome

Because symptoms overlap, doctors must rule out:

• Cervical disc herniation
• Carpal tunnel syndrome
• Cubital tunnel syndrome
• Rotator cuff injuries
• Peripheral neuropathy
• Pancoast tumor (rare)

Accurate diagnosis matters because treatment approaches differ.

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The Outlook

For most people, thoracic outlet syndrome improves with conservative treatment. Early recognition and posture correction make a meaningful difference.

However, ignoring progressive weakness, swelling, or circulation changes is not wise. While neurogenic thoracic outlet syndrome is rarely life-threatening, vascular types can become serious if untreated.

The key is proper evaluation—not panic.

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What You Should Do Next

If you suspect thoracic outlet syndrome:

1. Monitor your symptoms carefully.
2. Improve posture and reduce overhead strain.
3. Use a free AI-powered Thoracic Outlet Syndrome symptom checker to help identify patterns in your symptoms and prepare questions for your healthcare provider.
4. Schedule an appointment with a healthcare professional.
5. Speak to a doctor immediately if you develop swelling, discoloration, severe pain, or circulation problems.

Thoracic outlet syndrome is manageable—but only if properly evaluated. If symptoms are persistent, worsening, or affecting your strength or circulation, speak to a doctor. Some forms can become serious or even limb-threatening if ignored.

You deserve clarity and relief. With the right diagnosis and care plan, most people see real improvement and return to normal function.