Can an MRI of the brachial plexus appear normal 5 months after trauma resulting in ulnar and radial nerve palsy?

MRI Findings in Brachial Plexus Injury 5 Months Post-Trauma

Yes, an MRI of the brachial plexus can appear normal 5 months after trauma resulting in ulnar and radial nerve palsy, despite the presence of significant nerve dysfunction. 1, 2

Imaging Limitations in Brachial Plexus Injuries

• Standard MRI has limitations in detecting certain types of nerve injuries, particularly those involving microstructural changes that may not be visible on conventional sequences 1, 2
• The American College of Radiology acknowledges that research into brachial plexus imaging is ongoing, with newer techniques like diffusion tensor imaging showing promise but not yet routinely performed outside research settings 1
• Even with dedicated brachial plexus MRI protocols (which are essential), some nerve injuries may not demonstrate visible abnormalities despite causing clinical dysfunction 3, 2

Factors Affecting MRI Visibility of Nerve Injuries

• The type of nerve injury significantly impacts MRI findings - complete ruptures or avulsions are more likely to show abnormalities than stretching injuries 3, 4
• Post-traumatic complications like hematomas, neuromas, and scarring may be visible on MRI even when the nerves themselves appear normal 1
• The timing of imaging is critical - while immediate post-injury imaging may show edema and hemorrhage, these findings often resolve within weeks, potentially leading to a normal-appearing MRI at 5 months 3, 2

Clinical-Radiological Correlation

• There is often discordance between clinical findings and imaging results in peripheral nerve injuries 2
• Electrodiagnostic studies (EMG/NCS) may demonstrate abnormalities when MRI appears normal, making them essential complementary tests 3, 4
• In cases of ulnar and radial nerve palsy following brachial plexus trauma, the injury may be more distal or involve microstructural changes not visible on conventional MRI 2, 4

Imaging Protocol Considerations

• Specialized brachial plexus MRI protocols are required for proper evaluation - standard neck, chest, or spine protocols are inadequate 3, 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 2
• Even with optimal protocols, some nerve injuries may not be detectable on conventional MRI 1, 2

Management Implications

• A normal MRI does not rule out significant nerve injury and should not delay appropriate management when clinical and electrodiagnostic findings suggest nerve dysfunction 3, 4
• Surgical exploration may still be indicated in cases with persistent neurological deficits despite normal imaging 4
• For ulnar and radial nerve palsies specifically, nerve transfer procedures may be considered even with normal imaging if clinical deficits persist beyond 3-6 months 5, 6

Common Pitfalls to Avoid

• Relying solely on imaging findings without correlation to clinical and electrodiagnostic results 3, 2
• Using inadequate MRI protocols not specifically designed for brachial plexus evaluation 2
• Delaying appropriate management based on normal imaging findings when clinical deficits persist 4