Thoracic Outlet Syndrome (TOS) describes conditions where the nerves or blood vessels passing through the thoracic outlet become compressed. This narrow space, located between the collarbone and the first rib, is where the brachial plexus nerves and the subclavian artery and vein pass on their way to the arm. Because the resulting symptoms—such as pain, numbness, and tingling in the arm and hand—are highly varied and can mimic many other conditions, obtaining a precise diagnosis is often challenging. The diagnostic journey requires a coordinated effort between several different medical specialists to accurately identify the specific structure being compressed.
The Medical Professionals Guiding Diagnosis
The process of confirming Thoracic Outlet Syndrome often begins with a Primary Care Physician or a physical therapist who first suspects the diagnosis based on a detailed patient history and physical examination. They are usually the initial point of contact, noting symptoms often worsened by specific arm or neck movements. Given the complexity of the thoracic outlet, the next step involves a multidisciplinary team of specialists, each focused on a different potential cause of the compression.
Specialists are typically organized by the type of TOS they treat, which includes neurogenic, arterial, and venous types. A neurologist or a physiatrist is often consulted first if the symptoms primarily involve nerve issues, such as pain or numbness, pointing toward the most common form, neurogenic TOS. These specialists focus on the health of the brachial plexus, the network of nerves compressed by surrounding muscles or bone structures.
If the symptoms include arm swelling, a bluish discoloration, or a feeling of heaviness, a vascular surgeon becomes the primary specialist. Vascular surgeons investigate the compression of the subclavian artery or vein, which defines the arterial and venous forms of TOS. Orthopedic surgeons or pain management specialists may also be involved, particularly if the cause is structural, such as a cervical rib, or if the primary concern is chronic pain management.
Steps in Confirming a Thoracic Outlet Syndrome Diagnosis
Diagnosis relies on a combination of physical maneuvers, advanced imaging, and physiological testing to confirm the location and nature of the compression. The physical examination involves specific provocative maneuvers designed to replicate the patient’s symptoms by narrowing the thoracic outlet space. For example, the Roos test, or Elevated Arm Stress Test, requires the patient to hold their arms in a specific elevated position while opening and closing their hands. The reproduction of symptoms, such as numbness or fatigue, during this test suggests a compression of the neurovascular bundle.
Another common test is the Adson’s maneuver, where the examiner checks the radial pulse while the patient turns and extends their neck toward the affected side. A diminished or absent pulse during this movement suggests compression of the subclavian artery.
Imaging studies provide visual evidence of the structures in the thoracic outlet. Initial screening often includes an X-ray of the neck and chest to identify any bony abnormalities, such as an extra cervical rib, which is a congenital cause of compression. Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans are used to visualize the soft tissues, including the scalene muscles and fibrous bands that may be pressing on the nerves or vessels. These scans can be performed with the patient’s arm in different positions to simulate the compression that causes symptoms.
Physiological testing helps determine the functional impact of the compression on the nerves and blood flow. Nerve Conduction Studies (NCS) and Electromyography (EMG) measure how quickly electrical signals travel through the nerves and how muscles respond to those signals. While these tests are often normal in the most common neurogenic form of TOS, they are important for ruling out other nerve conditions and for confirming the rarer, true neurogenic form where there is clear nerve damage. Specialized vascular tests, like venography or arteriography, involve injecting a contrast dye into the veins or arteries to clearly visualize blood flow and identify any narrowing or blockage.
Distinguishing Thoracic Outlet Syndrome from Other Conditions
A significant challenge in diagnosing TOS is performing a differential diagnosis, which means systematically ruling out other conditions with similar symptoms. The pain and paresthesia (tingling/numbness) characteristic of TOS frequently overlap with symptoms caused by nerve or joint issues elsewhere in the body. Therefore, the diagnostic process functions as a diagnosis of exclusion until TOS is the most likely remaining cause.
One of the most common conditions to distinguish from TOS is cervical radiculopathy, which results from nerve root compression in the neck due to herniated discs or degenerative changes in the cervical spine. Both conditions can cause pain radiating down the arm, but cervical radiculopathy typically follows a more defined dermatomal pattern corresponding to a specific spinal nerve root. Peripheral nerve entrapment syndromes, such as Carpal Tunnel Syndrome at the wrist or Cubital Tunnel Syndrome at the elbow, also produce numbness in the hand and fingers that must be ruled out.
Vascular TOS symptoms, like swelling and arm discoloration, must be differentiated from other vascular pathologies. Deep Vein Thrombosis (DVT) in the arm requires immediate medical attention and presents differently than the chronic, positional compression seen in venous TOS. Conditions like Raynaud’s phenomenon, which causes episodes of reduced blood flow to the fingers, are also considered to ensure the symptoms are not due to a generalized vascular disorder rather than a localized compression.