Why does the radial artery pulse disappear with Adson's (Adson's test) maneuver?

Why the Radial Artery Pulse Disappears with Adson's Maneuver

The radial artery pulse disappears during Adson's maneuver due to compression of the subclavian artery as it passes through the thoracic outlet, typically caused by scalene muscle contraction, cervical rib, or other anatomical structures narrowing the neurovascular space during the provocative positioning. 1

Mechanism of Pulse Disappearance

The Adson's maneuver involves specific positioning that can compress the subclavian artery:

• Patient positioning: The patient sits upright with arms at their sides
• Examiner technique: The examiner palpates the radial pulse on the side being tested
• Provocative movements: The patient extends their neck, rotates their head toward the tested side, and takes a deep breath while holding it 1

During this maneuver, several anatomical changes occur:

1. Scalene muscle tension: The anterior and middle scalene muscles contract and narrow the interscalene triangle
2. Thoracic outlet narrowing: The space between the clavicle, first rib, and scalene muscles decreases
3. Subclavian artery compression: The artery becomes compressed as it passes through this narrowed space
4. Reduced distal flow: The compression reduces blood flow to the radial artery, causing diminished or absent pulse 2

Clinical Significance and Limitations

Despite its historical use, Adson's maneuver has significant limitations:

• High false-positive rate: The American College of Radiology notes that pulse changes during Adson's maneuver occur in many normal subjects without thoracic outlet syndrome 1
• Poor specificity: Studies have shown that 60% of normal individuals may demonstrate arterial compression with thoracic outlet maneuvers 3
• Limited diagnostic value: The test is considered to have "no clinical value" for diagnosing thoracic outlet syndrome according to current guidelines 1, 2

A 1990 study found that while clinical examination showed a 1% positive response rate for Adson's maneuver in healthy subjects, Doppler flowmetry showed 0% positive responses, suggesting that complete flow obstruction is rare even when pulse changes are detected 4.

More Reliable Diagnostic Approaches

For thoracic outlet syndrome evaluation, more reliable tests include:

• Elevated arm stress test (Roos test)
• Wright's test
• Halstead maneuver (costoclavicular maneuver)
• Supraclavicular pressure test 1, 5

Current evidence supports the use of the Halstead maneuver, Wright's test, Cyriax Release test, and supraclavicular pressure test for better diagnostic accuracy 5.

Potential Clinical Application

Despite its limitations as a diagnostic tool, Doppler scanning during Adson's maneuver may have some predictive value:

• A 2006 study suggested that duplex scanning of the subclavian artery during Adson's maneuver might help predict surgical outcomes in non-specific thoracic outlet syndrome
• 87.5% of patients with a positive Doppler Adson's test had complete symptom resolution after surgery, compared to only 50% with a negative test 6

Prevention and Management of Radial Artery Spasm

When performing procedures involving radial artery access, several measures can reduce spasm:

• Pharmacological interventions: Calcium channel blockers (verapamil 2.5–5 mg, diltiazem 2.5–5 mg, or nicardipine 250–500 μg) and nitroglycerin (100–200 μg) administered intra-arterially after sheath insertion 7
• Patient comfort: Local anesthesia, mild to moderate sedation, and a warm environment reduce anxiety, discomfort, and arterial spasm 7
• Technical considerations: Using appropriate catheter sizes and minimizing vessel trauma during procedures 7

Remember that while the radial pulse may disappear during Adson's maneuver, this finding alone is not sufficient to diagnose thoracic outlet syndrome and must be interpreted in the context of the patient's overall clinical presentation.