MRA Findings in TB Vasculitis Causing Pontine Infarct
In TB vasculitis causing pontine infarct, MRA will typically show stenosis or occlusion of the basilar artery and its branches, though MRA has limited sensitivity compared to vessel wall imaging and may appear normal despite active vasculitis.
Key MRA Findings
Luminal Abnormalities
- Stenosis and occlusion are the primary findings on MRA in tuberculous cerebral vasculitis, particularly affecting the basilar artery and its perforating branches that supply the pons 1, 2
- Multifocal stenoses may be visible on time-of-flight (TOF) MRA, with abnormalities detected in approximately 81% of patients with angiographic evidence of vasculitis 3
- The basilar artery and vertebrobasilar circulation are commonly involved in TB meningitis-related vasculitis 2
Critical Limitation of MRA Alone
- MRA may be completely normal despite active vasculitis—in one study, 17 of 45 patients with confirmed CNS vasculitis had no stenosis visible on MRA (MRA-negative vasculitis) 4
- MRA has limited resolution for detecting small vessel involvement, which is problematic since TB vasculitis frequently affects medium and small penetrating arteries 3
- Luminal imaging alone (MRA) has only 36% diagnostic accuracy compared to 89% when combined with vessel wall imaging 3
Superior Diagnostic Approach: Vessel Wall Imaging
Why VWI is Essential
- Vessel wall enhancement (VW-CE) is present in 66.3% of TB meningitis cases, even when MRA appears normal 1
- VWI demonstrates nodular or smooth segmental enhancement of vessel walls, which represents active inflammatory changes in TB vasculitis 1
- Concentric enhancement pattern is characteristic (88.3% of cases in CNS vasculitis), helping distinguish from atherosclerotic disease 4
Comparative Performance
- VWI has better sensitivity than MRA for detecting vascular complications in TB vasculitis 1
- MRA has better specificity but misses many cases of active inflammation 1
- There is significant association between vessel wall enhancement and infarctions in corresponding arterial territories 1
Recommended Imaging Protocol
Optimal Imaging Strategy
- Contrast-enhanced MRI brain with vessel wall imaging protocol plus TOF-MRA without contrast is the most appropriate approach for detecting CNS vasculitis 3
- Post-contrast T1-weighted sequences with high-resolution vessel wall imaging should be included 3, 5
- Standard brain sequences will show the pontine infarct itself with restricted diffusion on DWI 1, 2
Additional Parenchymal Findings
- Multiple infarcts of variable ages are common, with restricted diffusion indicating acute ischemia 3, 5
- Leptomeningeal enhancement is present in most TB meningitis cases (9 of 10 patients in one series) 2
- Hydrocephalus and tuberculomas may coexist 2
Clinical Pitfalls to Avoid
Common Diagnostic Errors
- Do not rely on MRA alone—normal MRA does not exclude TB vasculitis, as vessel wall inflammation may be present without significant luminal narrowing 4
- Overlap with other conditions: MRA findings of stenosis are non-specific and can mimic atherosclerosis or reversible cerebral vasoconstriction syndrome 3
- Timing matters: VWI should be performed before or within 3 days of starting corticosteroids for optimal detection of active inflammation 6
Monitoring Considerations
- Persistent vessel wall enhancement does not always indicate treatment failure—VW-CE can remain stable despite clinical improvement and immunosuppressive therapy 4
- However, stable or progressive VW-CE is associated with higher relapse rates (14/30 cases) compared to regressing enhancement (5/25 cases) 4