Causes and Diagnoses

Causes and Diagnoses of Thoracic Outlet Syndrome

Thoracic outlet syndrome occurs when your collarbone and upper rib are close together, compressing important nerves and blood vessels. This can occur for a number of reasons:

• Congenital (present at birth) condition:
• Trauma to the neck, collarbone or first rib
• Repetitive stress injury, such as from lifting, typing or other repetitive movement
• Poor posture
• Extra pressure on joints from obesity
• Extra looseness of joints because of pregnancy

Your risk for thoracic outlet syndrome may also be higher if you have:

• A sleep disorder
• Stress
• Depression
• Injury to the back
• Tumor or enlarged lymph nodes in the upper chest or underarm

Diagnosing thoracic outlet syndrome

Diagnosis of thoracic outlet syndrome will begin with a physical exam in which your physician may ask you to move your neck, shoulders and arms to provoke symptoms. Other tests may include:

• Chest X-ray: This test can identify the presence of pneumonia or other blockages in the airway.
• Computed tomography (CT) scan: This test combines X-ray and computer technology to produce detailed cross-sectional images of your chest cavity.
• Nerve conduction tests: These tests measure and record muscle response through electrical nerve stimulation.
• Electromyography (EMG): This test measures the electrical potential of muscle fibers stimulated by electrical impulses. People with myasthenia gravis do not respond well to such electrical stimulation.

If the symptoms indicate blood vessel compression, your physician may also order:

• Doppler ultrasound: This type of imaging captures movement to detect any irregularities in blood flow through your thoracic outlet and into your arm.
• Magnetic resonance imaging (MRI): Magnetic resonance imaging (MRI) creates detailed images of organs and other body structures using a large magnet, a computer and radiofrequencies. Unlike computed tomography (CT or CAT) scans or X-rays, MRI does not use radiation.
• Angiogram: During an MRI or CT scan, your physician may inject intravenous dye to make the blood vessels more visible.
• Arteriography/Venography: Using a catheter inserted in the groin, your physician can follow the path of your arteries or veins to see where the compression is or to deliver medication to break up a blood clot.