From the Guidelines
Diagnosing thoracic outlet syndrome (TOS) requires a combination of clinical evaluation and diagnostic tests, with MRI being the most appropriate initial imaging test for patients with neurogenic TOS, as it provides high-resolution images of the brachial plexus and surrounding structures 1.
Clinical Evaluation
A thorough medical history and physical examination are essential, focusing on symptoms like pain, numbness, or weakness in the neck, shoulder, arm, or hand. Specific physical tests include:
- Adson's test (checking pulse while the patient turns their head and takes a deep breath)
- The elevated arm stress test (holding arms above shoulder level until symptoms appear)
- The costoclavicular maneuver (bringing shoulders backward and downward)
Diagnostic Tests
Imaging studies are often necessary, including:
- X-rays to check for cervical ribs or bone abnormalities
- MRI or CT scans to visualize soft tissues and blood vessels
- Vascular studies like ultrasound or angiography to assess blood flow
- Nerve conduction studies and electromyography to evaluate neurological involvement
- Diagnostic local anesthetic injections can sometimes confirm the diagnosis by temporarily relieving symptoms
Imaging Protocols
For patients with neurogenic TOS, MRI without IV contrast is an acceptable initial imaging test, as it provides high-resolution images of the brachial plexus and surrounding structures 1. For patients with venous TOS, US duplex Doppler, CT with IV contrast, or catheter venography are equivalent alternatives for initial and follow-up imaging 1. For patients with arterial TOS, CTA with IV contrast, MRA without and with IV contrast, US duplex Doppler, or arteriography of the upper extremity are equivalent alternatives for initial and follow-up imaging 1.
Consultation with Specialists
Since TOS can mimic other conditions like cervical disc disease or carpal tunnel syndrome, a comprehensive approach is needed for accurate diagnosis, often requiring consultation with specialists in neurology, vascular surgery, or orthopedics 1.
From the Research
Diagnostic Approach
To diagnose thoracic outlet syndrome (TOS), a combination of history, physical examination, and imaging studies can be used 2, 3. The diagnosis of TOS is not a diagnosis of exclusion, and there should be evidence for a physical anomaly that can be corrected.
Clinical Presentation
Patients with TOS typically present with arm pain and swelling, arm fatigue, paresthesias, weakness, and discoloration of the hand 2. The most common neurologic signs are hypesthesia in the medial forearm or ulnar digits and weakness of the abductor pollicis brevis (APB) muscle 4.
Electrodiagnostic Studies
Electrodiagnostic studies, such as nerve conduction studies (NCS) and needle electromyography (EMG), can be useful in the diagnosis of neurogenic TOS 4, 5, 6. The medial antebrachial cutaneous (MABC) sensory nerve action potential amplitude is often decreased in patients with TOS 4, 5. A comprehensive electrodiagnostic examination of the lower plexus with contralateral comparison studies is imperative to diagnose this disorder accurately 6.
Imaging Studies
Imaging studies, such as brachial plexus MRI and computed tomography angiography (CTA), can be used to detect structural abnormalities, such as focal stenosis of the subclavian artery 4.
Diagnostic Criteria
The diagnosis of TOS can be established through a combination of:
- History of symptoms
- Physical examination findings
- Imaging studies
- Electrodiagnostic studies 2, 3, 4 Some key diagnostic criteria include:
- Evidence of neurovascular compression at the thoracic outlet
- Presence of physical anomalies, such as cervical ribs or fibrous bands
- Abnormal electrodiagnostic studies, such as decreased MABC sensory nerve action potential amplitude
- Structural abnormalities detected on imaging studies, such as focal stenosis of the subclavian artery 2, 4