Introduction
Meningiomas are the most common extra-axial intracranial tumors, arising from the arachnoid cap cells of the meninges. They are typically benign (WHO grade I), slow-growing tumors but can occasionally present with atypical or malignant features.
Radiology, especially MRI, plays a central role in diagnosis, surgical planning, and follow-up.
CT Imaging Features
- Well-circumscribed, extra-axial mass with broad dural attachment.
- Hyperdense or isodense to cortex on non-contrast CT.
- Intense homogeneous enhancement after contrast.
- Calcification (present in ~20%).
- Bone changes: hyperostosis (classic), less commonly bone erosion.
MRI Imaging Features (Modality of Choice)
Signal Characteristics
- T1-weighted: Iso- to hypointense relative to gray matter.
- T2-weighted: Iso- to hyperintense; may show intratumoral cysts.
- FLAIR: Can show surrounding vasogenic edema.
- DWI: Usually no restricted diffusion (except atypical variants).
Contrast Enhancement
- Intense, homogeneous enhancement in most cases.
- “Dural tail sign”: Linear enhancement of dura extending away from the tumor — highly suggestive but not pathognomonic.
Location & Growth Pattern
- Extra-axial with CSF cleft sign.
- May cause mass effect and cortical buckling.
- Common sites: parasagittal, convexity, sphenoid wing, olfactory groove, cerebellopontine angle.
Differential Diagnosis
- Schwannoma (especially in CPA region – “ice-cream cone” appearance, no dural tail).
- Metastasis (can mimic meningioma but usually lack dural tail and hyperostosis).
- Hemangiopericytoma (more aggressive, bone destruction rather than hyperostosis).
- Dural lymphoma (homogeneous enhancement but no calcification).
Role of Radiology in Management
- Diagnosis & grading: MRI features can suggest atypical/malignant variants (heterogeneous, necrotic, infiltrative margins).
- Surgical planning: Defines dural attachment, bone involvement, and relation to venous sinuses.
- Follow-up: Postoperative surveillance and recurrence detection.
- Advanced imaging: MR perfusion and spectroscopy may aid in differentiation from mimics.
Teaching Points
- Meningioma = extra-axial, dural-based, homogeneously enhancing mass.
- Dural tail sign is a key imaging clue but not exclusive.
- Look for calcification and hyperostosis on CT.
- Always consider mimics like metastasis or schwannoma, especially in atypical presentations.
Conclusion
Meningiomas are common, usually benign, and often have characteristic imaging findings. Recognizing these features ensures accurate diagnosis, appropriate surgical planning, and differentiation from mimics.
