Meningioma

Meningioma is the most common primary intracranial neoplasm (representing approximately 35-40% of all primary central nervous system tumors), arising from arachnoid meningothelial (cap) cells of the leptomeninges. WHO 2021 classification recognizes 15 histological subtypes grouped into three grades: WHO grade 1 (benign, 80-85% — meningothelial, fibrous, transitional, psammomatous, angiomatous, microcystic, secretory, lymphoplasmacyte-rich, metaplastic), grade 2 (atypical, 15-20% — atypical, clear cell, chordoid), and grade 3 (anaplastic, 1-3% — anaplastic/malignant, papillary, rhabdoid). Molecular profiling now incorporates NF2 mutation, TERT promoter mutation, BAP1 loss, CDKN2A/B deletion, and methylation classes for prognosis.

Epidemiology: incidence approximately 8-10 per 100,000 per year, female-to-male ratio 2:1 (estrogen and progesterone receptor expression), age peak in fifth-sixth decade, increased incidence with age, association with neurofibromatosis type 2 (NF2) and prior cranial radiation. Risk factors include ionizing radiation exposure (most established), female sex, hormone exposure (oral contraceptives, hormone replacement, breast cancer), obesity, NF2, multiple endocrine neoplasia type 1, schwannomatosis. Clinical presentation depends on location: parasagittal/falcine (motor/sensory deficits, leg weakness), convexity (focal seizures, headache), sphenoid wing (visual loss, proptosis, cranial neuropathy), olfactory groove (anosmia, frontal lobe syndrome), tuberculum sellae (visual field defects, optic chiasm compression), cerebellopontine angle (hearing loss, facial weakness, trigeminal neuralgia), foramen magnum (long tract signs, lower cranial neuropathy), spinal (radiculopathy, myelopathy).

Diagnosis is by MRI with gadolinium showing dural-based extra-axial mass with homogeneous enhancement and characteristic dural tail (60-72%), CT showing isodense to hyperdense mass with calcification (20-25%) and hyperostosis of adjacent bone, MR spectroscopy with elevated alanine and choline, perfusion imaging with elevated rCBV. Differential includes hemangiopericytoma, dural metastases, granulomatous disease, lymphoma. Treatment options: observation with serial imaging for small asymptomatic lesions especially in elderly; surgical resection (Simpson grade I-V resection determines recurrence risk) for symptomatic, growing, or large tumors; stereotactic radiosurgery (gamma knife, cyberknife) for small (<3 cm) lesions, residual disease, or surgical contraindications; fractionated radiotherapy for large or complex lesions; medical therapy for unresectable/recurrent disease (hydroxyurea, somatostatin analogs, bevacizumab, mTOR inhibitors — limited efficacy). Five-year recurrence rates by Simpson grade I (10%) to grade V (40%). WHO grade 2 and 3 require adjuvant radiotherapy and have 5-year survival of 60-78% and 22-67% respectively.