From the Guidelines
The diagnosis of thoracic outlet syndrome (TOS) should be approached with a combination of clinical evaluation and specialized tests, with MRI being the most useful imaging study for evaluating neurogenic TOS, as it can delineate extravascular anatomy and characterize soft tissues 1.
Diagnostic Approach
The diagnosis of TOS typically requires a combination of clinical evaluation and specialized tests. The most useful diagnostic studies include:
- Provocative physical examination maneuvers (Adson's test, elevated arm stress test, and Wright's test)
- Vascular studies (duplex ultrasound, arteriography, or venography)
- Neurophysiological studies (nerve conduction studies and electromyography)
- Imaging studies (chest X-ray, CT scan, or MRI) ### Imaging Studies For vascular TOS, angiography remains the gold standard, showing compression of vessels during arm positioning 2. For neurogenic TOS, which is the most common form, electrodiagnostic studies may show lower trunk brachial plexopathy, though these can be normal in many cases.
- MRI or MR neurography can help visualize nerve compression, and is particularly useful for evaluating the brachial plexus and cervical spine, as well as dynamic evaluation of neurovascular bundles in the costoclavicular, interscalene, and pectoralis minor spaces 1.
- CT evaluation of TOS is typically performed in “neutral” and “stressed” positions, and may be useful for evaluating the thoracic outlet and assessing adequate decompression after intervention 3.
Diagnostic Considerations
Diagnosis often requires ruling out other conditions with similar symptoms, such as cervical disc disease or peripheral nerve entrapment. Since no single test is definitive for TOS, diagnosis typically relies on a combination of clinical presentation, physical examination findings, and supportive diagnostic studies interpreted by specialists experienced with this condition 2. Some key points to consider when diagnosing TOS include:
- The use of provocative physical examination maneuvers to reproduce symptoms
- The importance of imaging studies, such as MRI or CT, to evaluate the thoracic outlet and assess for compression of neurovascular structures
- The need to rule out other conditions with similar symptoms, such as cervical disc disease or peripheral nerve entrapment
- The importance of interpreting diagnostic studies in the context of clinical presentation and physical examination findings.
From the Research
Diagnostic Tests for Thoracic Outlet Syndrome
- The diagnosis of thoracic outlet syndrome (TOS) can be established through history, physical examination maneuvers, and imaging 4.
- Dynamic CT angiography can be used to diagnose TOS by specifying the site of compression, its grade, and the existence of predisposing anatomical factors 5.
- Clinical, electrodiagnostic, and imaging features can be used to diagnose true neurogenic thoracic outlet syndrome (TN-TOS), including nerve conduction study (NCS) and needle electromyography (EMG) of the upper extremity 6.
- Physical exam is most important and includes several provocative maneuvers, such as neck rotation and head tilting, which elicit symptoms in the contralateral extremity 7.
Imaging Parameters
- Imaging parameters, including focused history and physical, provocative maneuvers, and imaging follow-up, can be used to diagnose arterial TOS (aTOS) 8.
- Brachial plexus MRI and computed tomography angiography (CTA) can be used to detect structural abnormalities in TN-TOS patients 6.
- Vascular stenosis of more than 50% on dynamic CT angiography is strongly associated with TOS 5.
Classification of TOS
- TOS can be classified as neurogenic, arterial, or venous based on the compressed structure(s) 4.
- Neurogenic TOS (NTOS) is by far the most common, comprising well over 90% of all TOS patients, while arterial TOS is the least common, accounting for no more than 1% 7.
- Each type of TOS has different symptoms and physical findings, which can be used to identify the type of TOS 7.