For a basilar artery aneurysm, is it better to do Magnetic Resonance Angiography (MRA) with or without contrast?

MR Angiography for Basilar Artery Aneurysm: With Contrast is Superior

For basilar artery aneurysms, MR angiography (MRA) with contrast is superior to non-contrast MRA due to better spatial resolution, decreased flow-related artifacts, and improved detection of aneurysm characteristics. 1

Imaging Options for Basilar Artery Aneurysms

MRA With Contrast

• Provides superior evaluation of vascular structures in the posterior circulation
• Offers increased spatial resolution compared to non-contrast techniques 1
• Reduces flow-related artifacts that can obscure small aneurysms
• Sensitivity for detecting aneurysms >3mm approaches 89% with experienced readers 1
• Particularly valuable for basilar artery imaging due to complex anatomy and proximity to brainstem

MRA Without Contrast

• Limited evidence supports its use for basilar artery aneurysms
• ACR Appropriateness Criteria specifically states "there is insufficient evidence to support the use of a noncontrast MRA" for vascular evaluation 1
• Time-of-flight techniques may miss smaller aneurysms or those with complex flow patterns
• May be considered only when contrast is absolutely contraindicated (severe renal dysfunction)

Clinical Decision Algorithm

1. First-line imaging: MRA with contrast

   • Provides optimal visualization of basilar artery and potential aneurysms
   • Allows better characterization of aneurysm morphology, neck, and relationship to perforating vessels

2. When contrast is contraindicated:

   • Consider CTA as an alternative (sensitivity 96.3%, specificity 100% with modern scanners) 1
   • Non-contrast MRA only if both contrast MRA and CTA are contraindicated
   • Digital subtraction angiography (DSA) remains the gold standard but is more invasive 1

Important Considerations

• Basilar artery aneurysms are particularly challenging to detect due to their location and surrounding bony structures
• Small aneurysms (<5mm) may be missed on non-contrast studies 1
• Contrast-enhanced MRA has demonstrated excellent reproducibility between examinations 1
• For follow-up of treated aneurysms, contrast-enhanced MRA has 92% sensitivity and 96% specificity compared to DSA 1

Potential Pitfalls

• Vessel tortuosity in the posterior circulation can lead to false positives on non-contrast studies
• Small perforator vessels arising from the basilar artery may be missed without contrast
• Susceptibility artifacts at the skull base can limit visualization on both contrast and non-contrast studies
• Contrast-enhanced MRA may underestimate residual aneurysm size in previously treated cases 1

The American Heart Association/American Stroke Association guidelines support MRA as useful for detection and follow-up of intracranial aneurysms (Class I; Level of Evidence B) 1, with contrast-enhanced techniques providing superior diagnostic information for basilar artery pathology.