What MRI protocol is recommended for a suspected skull-based meningioma in an adult patient?

MRI Protocol for Skull-Based Meningioma

Order MRI brain without and with IV contrast using a standardized protocol that includes high-resolution 3D T1-weighted sequences pre- and post-contrast, axial T2 FLAIR, diffusion-weighted imaging (DWI), susceptibility-weighted imaging (SWI), and axial T2-weighted sequences. 1

Essential MRI Sequences

Primary Sequences (Must Include)

• 3D T1-weighted gradient echo pre-contrast: Provides baseline anatomic detail and high-resolution imaging for small lesion detection 1
• 3D T1-weighted post-contrast: This is the single most important sequence for meningioma visualization, demonstrating the characteristic homogeneous dural-based enhancement, dural tail, and CSF cleft 1, 2
• Axial T2 FLAIR: Essential for demonstrating the CSF cleft between tumor and brain, evaluating vasogenic edema in adjacent parenchyma, and confirming extraaxial location 1, 3
• Axial DWI with ADC maps: Provides information about tumor cellularity, though meningiomas typically show variable diffusion characteristics 1, 4
• Axial SWI: Critical for detecting intratumoral calcifications, which occur in up to 50% of meningiomas, and for visualizing intratumoral blood products 1, 2
• Axial T2-weighted: Completes the standard protocol for comprehensive tissue characterization 1

Technical Specifications

• Use 3D isotropic sequences for T1-weighted imaging rather than 2D sequences, as they provide superior spatial resolution and better detection of small skull base lesions 2
• Post-contrast 3D T1 using fast spin-echo techniques is preferred over gradient echo to reduce vascular signal artifact 2
• Total acquisition time: Approximately 21-30 minutes on modern 3T systems 2

Contrast Administration

• Standard dose: 0.2 mL/kg (0.1 mmol/kg) of gadolinium-based contrast agent administered as rapid IV infusion or bolus 5
• Complete imaging within 1 hour after contrast administration 5
• Supplementary dose consideration: In adults with normal renal function and equivocal findings, a supplementary dose of 0.4 mL/kg (0.2 mmol/kg) may be given up to 30 minutes after the first dose 5

Advanced Imaging Considerations for Skull Base Meningiomas

When to Add Perfusion MRI

• Consider MR perfusion (DSC) as an adjunct for skull base meningiomas when grading is important, as meningiomas are highly vascular tumors and perfusion can help predict WHO grade 1, 3, 2
• Perfusion MRI is particularly useful when new findings emerge or when differentiating tumor from post-treatment changes 1

When to Add SSTR PET Imaging

SSTR PET (DOTATATE, DOTATOC, or DOTANOC) is particularly valuable for skull base meningiomas because morphologic tumor borders are difficult to assess by MRI alone in this location 1

Specific indications for adding SSTR PET include:

• Ambiguous MRI findings where tumor extent is unclear 1
• Treatment planning, especially for radiotherapy target volume definition, as SSTR PET detects osseous involvement with higher accuracy than MRI 1
• Suspected optic nerve sheath meningioma, as this entity consistently binds SSTR ligands 1
• Differentiating recurrence from post-treatment scar tissue 1

SSTR PET provides detection sensitivities superior to contrast-enhanced MRI alone and can identify small meningeal lesions previously undetected on MRI 1

Key Imaging Features to Identify

Classic Meningioma Characteristics

• Homogeneous dural-based enhancement with characteristic dural tail (tapering extension along adjacent dura) 1, 2
• CSF cleft between tumor and brain parenchyma, confirming extraaxial location 1
• Intratumoral calcifications visible on SWI sequences 1, 2
• Vasogenic edema in subjacent parenchyma on T2/FLAIR, though this doesn't reliably predict WHO grade 1

Red Flags for Meningioma Mimics

• Marked T2-hypo- or hyperintensity (atypical for meningioma) 1
• Absence of dural tail 1
• Dural displacement sign rather than dural attachment 1

Common Pitfalls to Avoid

• Don't rely on CT alone for skull base meningiomas, as CT has significantly inferior sensitivity compared to MRI and frequently misses small lesions, particularly in the internal auditory canal or cerebellopontine angle 2
• Don't skip contrast administration unless contraindicated, as post-contrast T1-weighted imaging is essential for optimal tumor delineation 1, 3
• Don't omit SWI sequences, as calcifications are common (up to 50% of cases) and provide important diagnostic information 2
• Screen for renal function before contrast administration, particularly in patients over 60 years, with hypertension, or diabetes, to avoid nephrogenic systemic fibrosis risk 5