Thoracic outlet syndrome (TOS) is a group of disorders that occur when blood vessels or nerves in the space between the collarbone and the first rib are compressed. This anatomical region, known as the thoracic outlet, serves as a passageway for important structures traveling from the neck to the arm. Symptoms can vary widely, often including pain, numbness, tingling, and weakness in the arms, hands, neck, or shoulder. Diagnosing TOS can be challenging due to its diverse presentation and symptoms that often overlap with other conditions.
Initial Assessment and Physical Examination
Evaluating suspected thoracic outlet syndrome typically begins with a thorough review of a patient’s medical history. A healthcare provider will inquire about the nature, duration, and aggravating factors of symptoms, alongside any relevant medical history or past injuries. This helps identify patterns that might point towards TOS. The physical examination involves observing the patient’s posture, looking for visible asymmetries, muscular imbalances, or subtle vascular changes in the affected limb.
Specific provocative maneuvers are used to reproduce symptoms by temporarily increasing compression on the neurovascular bundle. During Adson’s test, the patient turns their head toward the affected side, extends their neck, and takes a deep breath while the examiner monitors the radial pulse. A positive result, indicated by a diminished or absent pulse or the reproduction of symptoms, suggests compression, though some studies question its diagnostic accuracy. The Roos test, also known as the Elevated Arm Stress Test, involves the patient holding their arms elevated with bent elbows and repeatedly opening and closing their hands for up to three minutes. The reproduction of symptoms like pain, numbness, tingling, heaviness, or an inability to maintain the position indicates a positive test.
Another maneuver is the Wright’s test, where the arm is abducted to 90 degrees and then moved into hyperabduction overhead while the radial pulse is checked. A decrease in pulse or the onset of symptoms suggests compression in the subpectoral space. Throughout these tests, the examining physician observes for changes in pulse quality, tingling, pain, or weakness in the arm and hand.
Imaging and Nerve Studies
Beyond the physical examination, various tests support a diagnosis of thoracic outlet syndrome and rule out other conditions. X-rays are often among the first imaging tests performed, primarily to check for bony abnormalities such as a cervical rib, which is an extra rib extending from the neck. Magnetic resonance imaging (MRI) provides detailed views of soft tissues, allowing visualization of nerve compression, fibrous bands, or vascular issues. Performing an MRI with the arms in an elevated or provocative position can be useful in demonstrating compression.
Computerized tomography (CT) scans offer cross-sectional images, providing detail of bones and their relationship to blood vessels. When a dye is injected, a CT angiography (CTA) can identify the location and cause of blood vessel compression. For evaluating nerve function, nerve conduction studies (NCS) measure the speed and amplitude of electrical signals along peripheral nerves, helping identify nerve dysfunction or compression. Electromyography (EMG) assesses electrical activity within muscles, which can indicate nerve injury or muscle problems. While these nerve studies are valuable for assessing overall nerve health, their direct diagnostic accuracy for neurogenic TOS can be inconsistent due to the deep location of the affected nerves.
Vascular studies are employed when blood vessel compression is suspected. Doppler ultrasound is a non-invasive test that uses sound waves to visualize blood flow and detect arterial or venous compression. More detailed assessments, such as magnetic resonance angiography (MRA) or conventional angiography, involve injecting a contrast dye to visualize blood vessels and assess blood flow, identifying any blockages or points of compression. Venography, a type of angiography, is used to diagnose compression of the subclavian vein.
Differentiating Thoracic Outlet Syndrome
The diagnosis of thoracic outlet syndrome is challenging because its symptoms can resemble those of many other conditions. This overlap necessitates a careful diagnostic process. Conditions such as carpal tunnel syndrome, which involves nerve compression at the wrist, can produce similar sensations of numbness and tingling in the hand. However, TOS symptoms might affect all fingers and often include associated pain in the neck or shoulder, whereas carpal tunnel syndrome typically impacts the thumb, index, middle, and a portion of the ring finger, usually sparing the pinky.
Cervical radiculopathy, a condition where a nerve in the neck is pinched, also causes pain, numbness, and weakness that can radiate down the arm, mimicking TOS symptoms. Rotator cuff injuries, affecting the shoulder, can lead to pain, weakness, and limited arm movement that might be mistaken for TOS. Other conditions, including brachial plexopathy, peripheral neuropathy, cubital tunnel syndrome, and various musculoskeletal imbalances, can also present with similar symptoms. Healthcare providers combine patient history, physical examination, and specific imaging and nerve studies to rule out other conditions.
Confirming a Diagnosis and Next Steps
A diagnosis of thoracic outlet syndrome is usually established through a combination of clinical findings and supportive results from various diagnostic evaluations. In some instances, a diagnostic injection, such as a scalene muscle block with local anesthetic, may be performed. If the injection temporarily relieves the patient’s symptoms, it further supports a diagnosis of TOS.
Once a diagnosis of TOS is confirmed, the next steps involve consulting with appropriate specialists. This may include vascular surgeons for vascular forms of TOS, neurologists for nerve-related symptoms, or physical therapists for conservative management. These specialists work together to develop a comprehensive management plan tailored to the specific type and severity of the thoracic outlet syndrome identified. The goal is to address the underlying compression and alleviate the patient’s symptoms.