What is the diagnostic test for Thoracic Outlet Syndrome (TOS) and subclavian artery stenosis?

From the Guidelines

The most appropriate diagnostic test for thoracic outlet syndrome (TOS) and subclavian stenosis is contrast-enhanced 3-D MR angiography (MRA) or CT angiography (CTA), as they provide detailed images of the subclavian artery and surrounding structures, and can help identify compression, stenosis, or other abnormalities.

Diagnostic Approach

When evaluating patients with suspected TOS or subclavian stenosis, a combination of clinical evaluation and imaging studies is necessary. The initial approach involves provocative maneuvers such as Adson's test, Wright's test, and the elevated arm stress test (EAST) to reproduce symptoms by compressing the neurovascular bundle.

Imaging Studies

Imaging studies for TOS include:

• Chest X-rays to identify cervical ribs or anatomical abnormalities
• MRI or MR angiography to visualize soft tissue compression
• CT angiography to assess vascular structures
• Nerve conduction studies and electromyography to help diagnose neurogenic TOS For subclavian stenosis, duplex ultrasonography is the first-line imaging test, measuring blood flow and visualizing the vessel.

Recommended Tests

Contrast-enhanced 3-D MRA or CTA is recommended as the primary imaging modality 1, as they provide detailed images of the subclavian artery and surrounding structures, and can help identify compression, stenosis, or other abnormalities. These tests should be selected based on clinical presentation, with vascular studies prioritized for suspected vascular TOS or subclavian stenosis, and neurological tests for neurogenic TOS.

Key Considerations

Early diagnosis is crucial as delayed treatment can lead to permanent nerve damage or vascular complications. The choice of diagnostic test should be based on the clinical presentation and suspected type of TOS or subclavian stenosis. Some key points to consider when interpreting imaging studies include:

• Arterial compression is assessed by using arterial cross-sections produced by sagittal reformation of data
• Sagittal reformation can show the location and severity of the arterial compression
• Volume-rendered images allow simultaneous analysis of bones and subclavian artery
• Arterial stenosis is expressed as the percentage of reduction of the cross-sectional area or the diameter of the artery 1

From the Research

Diagnostic Tests for TOS and Subclavian Stenosis

• The diagnosis of Thoracic Outlet Syndrome (TOS) is complex and requires a combination of physical examination, medical history, and diagnostic tests 2, 3, 4, 5.
• The Adson Test, which notes a radial pulse deficit in provocative positions, has been shown to be of no clinical value and should not be relied upon to make the diagnosis of any of the three types of TOS (arterial, venous, or neurogenic) 2.
• Color Doppler sonography has been shown to be 92% sensitive and 95% specific for the diagnosis of TOS, particularly in the evaluation of subclavian vein compression and thrombosis 4.
• Ultrasound can be used to localize and measure the degree of vascular stenosis, and is a useful tool in the diagnosis of venous TOS 6.
• Computed tomography and magnetic resonance imaging angiography and venography can also be used to demonstrate dynamic compression of the neurovascular structures in TOS 3.
• The diagnosis of subclavian stenosis can be made using imaging studies such as x-rays, which can disclose a cervical rib or anomalous first rib, and Doppler sonography, which can show significant compression of the subclavian artery 2, 4.
• The clinical significance of compression of the subclavian artery cannot be determined from some studies due to the small number of patients involved 4.
• Adjunct diagnostic studies frequently confirm the diagnoses of venous TOS and arterial TOS, but not of neurogenic TOS 5.