Yes, Guillain-Barré Syndrome Causes Post-Contrast Enhancement of Cauda Equina Nerve Roots
GBS characteristically produces gadolinium enhancement of cauda equina nerve roots on MRI, occurring in approximately 83-95% of cases, making this a highly sensitive imaging finding that supports the diagnosis. 1, 2
Mechanism and Pathophysiology
The enhancement pattern reflects breakdown of the blood-nerve barrier due to inflammatory infiltration characteristic of GBS. 3 The pathological changes in GBS predominate in proximal nerves, particularly at sites where spinal roots unite to form spinal nerves, with endoneurial inflammatory edema as the outstanding early feature. 4
Specific Enhancement Patterns
Two distinct enhancement patterns occur on gadolinium-enhanced MRI: 5
- Anterior root enhancement only (75% of cases): This pattern is strongly suggestive of GBS and particularly characteristic of acute motor axonal neuropathy (AMAN) variants 4, 5
- Both anterior and posterior root enhancement (25% of cases): Less specific but still consistent with GBS 5
All patients demonstrate thickening of intrathecal spinal nerve roots and cauda equina with varying degrees of enhancement on T1-weighted post-contrast sequences. 5
Diagnostic Utility
MRI nerve root enhancement is not part of routine diagnostic evaluation for GBS but serves as a sensitive supporting feature, particularly valuable when clinical or electrophysiological findings are equivocal. 1 The American Academy of Neurology notes this finding is especially useful in young children where clinical and electrophysiological assessment may be challenging. 1
The sensitivity is remarkably high: 2
- 83% overall sensitivity for acute GBS
- 95% sensitivity in typical GBS presentations
- Present even when EMG shows only minimal abnormalities (prolonged F-waves)
Clinical Correlations
Prominent nerve root enhancement correlates with specific clinical features: 2
- Severe back or leg pain: 60% of patients with prominent enhancement versus 10% with mild/no enhancement
- Higher GBS disability grade at presentation
- Longer recovery time: Significantly fewer patients with prominent enhancement could walk independently by 2 months
Timing Considerations
Enhancement typically appears early in the disease course. Studies show positive findings as early as 2 days after symptom onset, with mean detection at 13 days. 2 The enhancement and nerve root thickening diminish on follow-up imaging as clinical symptoms improve. 5
Important Caveats
While highly sensitive, cauda equina enhancement is not specific to GBS. 1, 5 The differential diagnosis includes:
- Leptomeningeal malignancy 6
- Other inflammatory polyradiculitides 6
- Neoplastic infiltration 5
- Infectious causes 6
However, the pattern of selective anterior root enhancement is strongly suggestive of GBS and helps narrow the differential. 5
Practical Application
When GBS is suspected but electrophysiological studies are normal or equivocal (common within the first week), gadolinium-enhanced MRI of the lumbosacral spine can provide crucial diagnostic support. 1, 2 This is particularly valuable in cases presenting with atypical features such as prominent low back pain as the initial symptom. 7
The ASCO guideline for immune-related adverse events specifically recommends MRI spine with and without contrast to evaluate for nerve root enhancement/thickening when GBS is suspected. 6