Purpose of MRI of the Brachial Plexus for Brachial Plexopathy
MRI of the brachial plexus is the gold standard imaging modality for diagnosing brachial plexopathy due to its superior soft-tissue contrast and spatial resolution, providing detailed definition of intraneural anatomy and localization of pathologic lesions when clinical and electrodiagnostic findings are nonspecific. 1, 2
Diagnostic Capabilities
- MRI can detect and characterize various etiologies of brachial plexopathy including tumors, inflammatory conditions, and compressive lesions with high accuracy (sensitivity 81%, specificity 91%, accuracy 88%) 1
- MRI provides additional diagnostic information beyond clinical evaluation and electrodiagnostic studies in approximately 45% of patients 1
- MRI can reliably differentiate compressive from non-compressive plexopathy 1
- MRI allows visualization of the entire course of the brachial plexus from the spinal cord to the axilla, which other imaging modalities cannot fully evaluate 1
Technical Considerations
- Dedicated brachial plexus MRI protocols are essential and differ significantly from routine neck, chest, or spine MRI protocols 1, 2
- Optimal protocols include orthogonal views through the oblique planes of the plexus with T1, T2, fat-saturated T2 or STIR, and fat-saturated T1 postcontrast sequences 1, 2
- MRI with IV contrast can provide additional information over non-contrast studies, particularly for detecting and characterizing masses, tumors, and inflammatory conditions 1, 3
- 1.5 Tesla MRI may be preferable when metal is present in the area to reduce artifact 1, 2
Clinical Applications
Non-traumatic Brachial Plexopathy
- MRI helps identify and characterize:
- Intrinsic nerve sheath tumors (neurofibromas, schwannomas) 1, 4
- Inflammatory/autoimmune conditions (brachial neuritis, chronic inflammatory demyelinating polyneuropathy) 1, 5
- Extrinsic compression from adjacent structures or masses 1
- Malignant involvement of the plexus (primary or metastatic) 4
- Radiation-induced plexopathy 4
Traumatic Brachial Plexopathy
- MRI can:
- Differentiate pre-ganglionic (root avulsion) from post-ganglionic injuries 1, 6
- Identify pseudomeningoceles as surrogate markers for root avulsion 1
- Assess nerve integrity to differentiate minor stretching injuries from complete nerve disruptions 1
- Detect post-traumatic complications like hematomas, neuromas, and scarring 1
- Evaluate surgical repairs in the post-treatment setting 1
Comparison to Other Imaging Modalities
- MRI is superior to CT cervical spine for brachial plexopathy as CT cannot fully visualize preganglionic nerve roots and has limited soft-tissue contrast resolution 1
- MRI is superior to cervical spine MRI for brachial plexopathy as cervical spine MRI does not evaluate the plexus lateral to the neural foramina 1
- Ultrasound has limited utility as a primary imaging modality for brachial plexopathy but may serve as a useful supplemental test in selected centers 1
- FDG-PET/CT is not recommended for non-traumatic brachial plexopathy unless there is a known malignancy 1
Common Pitfalls and Caveats
- For traumatic plexopathy, imaging should ideally be delayed until approximately one month after trauma to allow for resolution of hemorrhage and edema 1, 2
- Clinical overlap between radiculopathy and plexopathy can be challenging; in cases of diagnostic uncertainty, cervical spine MRI may be complementary to brachial plexus MRI 1, 3
- Standard MRI protocols for the neck, chest, or spine are inadequate for proper evaluation of the brachial plexus; specialized brachial plexus protocols are required 1, 2
- The appropriate CPT code for brachial plexus MRI depends on the clinical indication and may vary across institutions 1