What is Thoracic Outlet Syndrome?

Thoracic outlet syndrome (TOS) is a complex group of conditions that occurs when nerves or blood vessels in the space between your collarbone and first rib become compressed or squeezed. While the name may sound intimidating, understanding this condition can help patients recognize symptoms and seek appropriate treatment.

Understanding the Anatomy

The thoracic outlet is the narrow space formed by the top ribs, just below the collarbone, through which important structures pass from the neck to the arm. These include the brachial plexus (a network of nerves), the subclavian artery, and the subclavian vein. When these structures become compressed in this tight space, it results in thoracic outlet syndrome.

The Three Types of Thoracic Outlet Syndrome

Neurogenic TOS (95% of cases)

This is by far the most common type, representing about 95% of all TOS cases. It occurs when there's pressure on the brachial plexus, the network of nerves that travel from the neck to the arm. Most people receive a diagnosis in their 30s, and the most common causes are repetitive stress injuries (often from sports) and sudden trauma to the neck (like whiplash).

Venous TOS (4% of cases)

This involves compression of the subclavian vein and is more common among males, typically in their 20s or 30s. A person usually feels symptoms in their dominant arm.

Arterial TOS (1% of cases)

This is the rarest type, 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. This type usually happens due to anatomical differences that you're born with, such as a cervical rib.

Common Symptoms

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.

Neurogenic TOS symptoms include:

• A vague, aching pain in the neck, shoulder, arm, or hand
• Pain, numbness, or tingling on the inside of the forearm and the fourth and fifth fingers of the hand
• Weakness in hand muscles, which can result in loss of dexterity

Vascular TOS symptoms may include:

• Swelling, redness, or discoloration of the arm
• Exercise-induced arm discomfort resulting from insufficient blood flow to the arm
• Pain, numbness, tingling, cold sensation, pale/mottled hand or fingers with black spots

Who Gets Thoracic Outlet Syndrome?

TOS is more common in women and usually starts between 20 and 50 years of age. Musicians, athletes (especially those who train their upper bodies with weights), and employees who continuously use their lower neck and upper extremities are at higher risk.

The Role of Cervical Ribs

Between 1 and 3 percent of the population has a cervical rib—an extra rib that grows from the cervical spine (the neck part of the spine). Having a cervical rib increases the chance of nerve or blood vessel compression, though only about 10% of people with cervical ribs develop TOS. Many people with a cervical rib never know it, because the bone is often tiny and isn't noticed, even in X-rays.

Diagnosis: A Complex Process

Diagnosing TOS can be challenging because there may be many symptoms to explain, and it can mimic other conditions. Often, there is not a clear and obvious way to diagnose thoracic outlet syndrome. Healthcare providers diagnose TOS by performing a physical exam and reviewing your medical history, including movement-based tests where they ask you to perform simple movements like lifting your arms, tilting your head and clenching your fists.

Diagnostic tests may include:

• Duplex ultrasound to check for stenosis (narrowing) or occlusion (blockage) of blood vessels
• Chest X-ray to check for cervical rib or abnormal first rib
• Electromyography (EMG) to evaluate for peripheral nerve entrapment
• MRI to evaluate for cervical spine disease or intrinsic shoulder disease

Treatment Options

Physical therapy is typically the first treatment and is the most common initial treatment for neurogenic TOS. A physical therapist helps you increase your range of motion in your neck and shoulders, strengthens your muscles, and promotes better posture. Most people with neurogenic TOS see an improvement in symptoms.

Conservative Treatment

• Exercises that help strengthen the muscles surrounding the shoulder so that they are better able to support the collarbone
• Postural exercises that help you stand and sit straighter, which lessens the pressure on the nerves and blood vessels
• Stretching and strengthening exercises that reduce pressure on nerves and blood vessels
• Pain medications and anti-inflammatory drugs

Advanced Treatment

• Botulinum toxin injections, which are sometimes effective when physical therapy doesn't completely relieve symptoms
• Brachial plexus block with local anesthetic injected into the scalene muscles of the neck

Surgical Treatment

If symptoms persist after physical therapy and injections, surgery may be recommended. Surgery can involve cutting small muscles of the neck (anterior and middle scalene) and removing the cervical or first rib. Surgery is usually recommended for arterial TOS and may involve removing both the scalene muscles in the neck, the cervical rib if present, and the first rib.

Prognosis and Recovery

Most people recover with appropriate treatment. Following surgery, patients have a short inpatient hospital stay and then are discharged home, active and able to perform daily activities. However, sometimes neurogenic TOS recurs months or years after treatment, which may happen because of scar tissue from the surgical site or because the condition was misdiagnosed.

When to Seek Medical Attention

Without treatment, thoracic outlet syndrome can lead to serious complications, including chronic arm swelling and pain, permanent nerve damage, and in severe cases, pulmonary embolism. If you experience persistent pain, numbness, tingling, or weakness in your arm, shoulder, or hand—especially if symptoms worsen with certain arm positions—consult with a healthcare provider for proper evaluation.