Thoracic Outlet Syndrome (TOS) is characterized by the compression of nerves or blood vessels as they pass through the narrow passageway between the neck and the armpit. This compression leads to symptoms including pain, numbness, and weakness in the shoulder, arm, and hand. Since TOS symptoms often mimic other conditions, diagnosis relies heavily on specific provocative maneuvers, known as “special tests.” These tests temporarily recreate the compression and reproduce the patient’s familiar symptoms, helping clinicians pinpoint the source of the issue.
Understanding Thoracic Outlet Syndrome
The thoracic outlet is the small space bounded by the collarbone, the first rib, and the neck muscles. This area is a bottleneck for the neurovascular bundle, which includes the brachial plexus nerves, the subclavian artery, and the subclavian vein, all traveling to the upper extremity. Compression of these structures causes the symptoms associated with TOS.
TOS is categorized into three main types based on the compressed structure. Neurogenic TOS (nTOS) is the most common form, involving the brachial plexus nerves and accounting for over 90% of cases. Arterial TOS (aTOS) and Venous TOS (vTOS) are less frequent, involving the subclavian artery or vein, respectively, and often leading to circulatory symptoms like color changes or swelling. Different special tests are sensitive to particular types of compression.
Primary Positional Tests: Adson’s and Wright’s Maneuvers
Adson’s and Wright’s maneuvers are two frequently performed positional tests that assess for arterial or neurovascular compression by placing the arm and neck in positions that narrow the thoracic outlet. These tests rely on the obliteration of the radial pulse or the reproduction of symptoms to indicate a positive result.
Adson’s Maneuver
Adson’s Maneuver is designed to identify compression of the subclavian artery and brachial plexus within the interscalene triangle (the space formed by the scalene muscles). The clinician palpates the radial pulse while the patient extends the neck, rotates the head toward the tested side, and takes a deep breath to tense the scalene muscles. A positive result is indicated by a significant decrease or complete loss of the radial pulse, or the reproduction of the patient’s pain or numbness. However, pulse changes alone are not definitive, as many asymptomatic individuals can experience a diminished pulse during this test.
Wright’s Test
The Wright’s Test, or Hyperabduction Maneuver, focuses on compression beneath the pectoralis minor tendon and the coracoid process (the retropectoralis minor space). To perform this test, the patient’s arm is moved into a position of high abduction, often overhead, while the clinician monitors the radial pulse. The hyperabducted position tightens the pectoralis minor muscle, compressing the neurovascular bundle against the chest wall. A positive test is indicated by the weakening or disappearance of the radial pulse (suggesting axillary artery compression) or the reproduction of the patient’s neurological symptoms down the arm.
The Elevated Arm Stress Test (Roos Test)
The Elevated Arm Stress Test (EAST), also known as the Roos Test, is a distinct provocative maneuver because it requires sustained effort rather than a quick positional change. This test is considered highly sensitive for Neurogenic TOS, as it is designed to stress the compromised nerve tissue over a period of time.
The procedure involves the patient holding both arms in a “surrender” position, with shoulders and elbows bent to 90 degrees. While maintaining this posture, the patient rapidly opens and closes their hands for up to three minutes. This action increases the metabolic demand of the forearm muscles, subsequently increasing the blood flow requirement to the extremity.
A positive result is defined by the patient’s inability to complete the full three-minute duration due to the reproduction of familiar symptoms, not by the loss of the radial pulse. These symptoms typically include the onset of pain, heaviness, paresthesia, or numbness in the hand and forearm, often forcing the patient to drop their arms. The test’s ability to exacerbate neurological symptoms by sustaining the narrowed thoracic outlet space makes it a valuable tool for assessing nerve compression.
Limitations of Special Tests and Confirmatory Diagnosis
While special tests are useful for screening and guiding the physical examination, they are not definitive diagnostic tools for Thoracic Outlet Syndrome. These maneuvers often demonstrate good sensitivity, meaning they are effective at identifying individuals who have the condition, but they have poor specificity. This low specificity means they frequently produce false-positive results in healthy or asymptomatic individuals, or in patients with other conditions like carpal tunnel syndrome or cervical issues.
Because of these limitations, a definitive TOS diagnosis requires a multimodal approach beyond the physical exam. Imaging is often required to rule out other causes and confirm the site of compression. Objective testing is also performed to confirm specific involvement:
- X-rays can identify bony abnormalities like a cervical rib.
- Magnetic Resonance Imaging (MRI) evaluates soft tissues and the brachial plexus.
- Nerve Conduction Studies (NCS) and Electromyography (EMG) confirm neurogenic involvement.
- Venography or arteriography confirms vascular compression.