What is the recommended approach to evaluate the brachial plexus in a patient who cannot undergo MRI due to MRI‑incompatible implants?

Brachial Plexus Evaluation When MRI is Contraindicated

In patients unable to undergo MRI due to implanted devices, CT with intravenous contrast is the recommended next-line imaging modality for brachial plexus evaluation, offering the highest level of anatomic visualization after MRI. 1

Primary Alternative: CT Imaging

• CT neck with IV contrast receives an appropriateness rating of 6 ("may be appropriate") for nontraumatic brachial plexopathy when MRI cannot be performed 1
• CT provides the next highest level of anatomic visualization after MRI and can evaluate for adjacent soft-tissue lesions or tumors that may involve the plexus 1
• CT with IV contrast is superior to CT without contrast in this setting because it can better detect and characterize soft-tissue masses and tumors in the differential diagnosis of brachial plexopathy 1
• In traumatic cases, CT can characterize local osseous or vascular anatomy and injury 1

Context-Specific Recommendations

For Known Malignancy or Post-Treatment Syndrome

• FDG-PET/CT whole body receives an appropriateness rating of 7 ("usually appropriate") as either complementary to MRI or as an alternative when MRI cannot be performed 1
• PET/CT is particularly beneficial to differentiate radiation plexitis from tumor recurrence in patients with new symptoms after regional radiation therapy 1
• This modality can identify the extent of tumor involvement but provides limited resolution of the plexus itself 1

Ultrasound Considerations

• Ultrasound neck receives a low appropriateness rating of 2 ("usually not appropriate") for brachial plexopathy evaluation 1
• Ultrasound imaging of the brachial plexus is highly operator-dependent and has not gained widespread use for diagnosis of plexopathies 1
• However, it can be useful for image-guided therapy procedures 1

Modalities to Avoid

• Myelography and post-myelography CT cervical spine receives an appropriateness rating of 3 ("usually not appropriate") for nontraumatic plexopathy 1
• Myelography cannot evaluate the plexus directly lateral to the neural foramina and is not routinely performed for plexopathy evaluation 1
• CT cervical spine alone cannot visualize the preganglionic nerve roots adequately and does not fully evaluate the postganglionic brachial plexus due to narrow field of view and limited soft-tissue contrast resolution 1

Important Technical Considerations

• If metal implants are present in the area of clinical concern, consider that 1.5 Tesla MRI may be beneficial to reduce artifact if the implant is MRI-conditional rather than absolutely contraindicated 1
• Verify the specific implant type and manufacturer specifications, as some newer implants may be MRI-conditional under certain parameters
• Standard neck, chest, or spine CT protocols are not equivalent to dedicated plexus imaging and should not be considered adequate alternatives 1

Clinical Pitfalls

• Do not accept routine neck or cervical spine imaging as a substitute for dedicated brachial plexus evaluation, as these studies use different imaging planes and fields of view 1
• CT without IV contrast (appropriateness rating 4) provides significantly less diagnostic information than CT with contrast for soft-tissue pathology 1
• FDG-PET/CT should not be used for routine nontraumatic plexopathy without known malignancy (appropriateness rating 1) 1