Meningiomas
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Direct answer
Meningiomas are slow-growing, extra-axial tumours of arachnoid cap cells and are among the commonest primary intracranial tumours, typically in middle-aged and older women. They enhance homogeneously on CT and MRI with a broad dural base, a dural tail and often hyperostosis of the adjacent bone, and are graded WHO 1 to 3, with brain invasion or raised mitotic activity lifting them to grade 2 (atypical). Management spans observation for small asymptomatic tumours, Simpson-graded surgical excision for symptomatic or enlarging lesions, and stereotactic radiosurgery for skull base or residual tumours.
What you must remember
- Imaging signature: extra-axial mass with broad dural base, intense homogeneous contrast enhancement, dural tail, plus hyperostosis or calcification on CT; a cerebrospinal fluid cleft between tumour and cortex confirms the extra-axial plane.
- WHO grading: grade 1 benign (meningothelial, transitional, psammomatous and others), grade 2 atypical (brain invasion or increased mitoses, among criteria), grade 3 anaplastic — recurrence risk climbs with grade.
- Simpson grading of surgical excision: I total removal of tumour, dural attachment and abnormal bone; II total removal with coagulation of dural attachment; III removal without resecting the dural attachment; IV subtotal; V decompression or biopsy — recurrence falls steeply from grade I to V.
- Common sites: convexity, parasagittal or olfactory groove, sphenoid wing, suprasellar, spinal; parasagittal lesions may invade the superior sagittal sinus, dictating staged or partial strategies.
- Observation is legitimate for small asymptomatic tumours, incidentally found, with periodic MRI; growth or symptom onset moves to treatment.
- Stereotactic radiosurgery is effective for small residual or skull base meningiomas, particularly cavernous sinus lesions wrapped around the carotid artery.
- Aggressive variants and grading pitfalls: radiation-induced meningiomas are often multiple or atypical; clear-cell, chordoid and atypical tumours recur and warrant radiotherapy after subtotal excision.
Common confusion
The dural tail is mistaken as pathognomonic — it is supportive but can occur with dural metastasis and other lesions, so it is not a substitute for tissue when imaging is atypical. Extra-axial versus intra-axial location is the first fork in every stem: the CSF cleft, the broad dural base and grey matter displacement outward settle it. Finally, candidates conflate the WHO grade of the tumour with the Simpson grade of the operation — one describes biology, the other the extent of resection, and exam questions deliberately ask for the latter.
Exam-focused takeaway
Meningioma questions cluster on three axes: imaging recognition (homogeneous enhancement, dural tail, hyperostosis), the Simpson ladder — know all five grades verbatim — and management selection by size, site and symptoms. A convexity tumour in a fit patient earns a Simpson I excision; a cavernous sinus lesion wraps around the carotid and leans toward radiosurgery or partial decompression; an incidental small convexity lesion in an elderly patient earns observation with MRI. Expect one stem on female preponderance and progesterone receptors, and another on recurrence after higher Simpson grades.
Frequently asked questions
What is the typical imaging appearance of a meningioma?
A homogeneously enhancing extra-axial mass with a broad dural base and dural tail on MRI, often with hyperostosis or calcification on CT.
What does Simpson grade I excision mean?
Total removal of the tumour together with its dural attachment and any abnormal bone — the lowest recurrence of all five Simpson grades.
Which meningiomas can simply be observed?
Small, asymptomatic, incidentally discovered tumours in older patients, followed with periodic MRI, with treatment reserved for growth or new symptoms.
Why are cavernous sinus meningiomas often treated with radiosurgery?
Because surgical access risks the carotid artery and cranial nerves three, four and six, radiosurgery offers control with preserved function for smaller lesions.
What raises a meningioma to WHO grade 2?
Atypical features, including brain invasion and increased mitotic activity, place it in grade 2 with a higher recurrence risk.