Key Facts

Meningiomas are common, usually benign, and often discovered incidentally. Many can be managed conservatively with serial imaging. Surgical resection is curative for most WHO grade 1 tumours.

Epidemiology

Most common primary intracranial tumour: ~36% of all primary brain tumours. Incidence ~8 per 100,000/year. F:M 2:1. Increases with age (peak 60-70 years). Incidental meningiomas found in ~1-3% of brain MRIs.

Aetiology

• Prior cranial radiotherapy: strongest risk factor (15-25 year latency)
• NF2: multiple meningiomas; NF2 gene (merlin/schwannomin) on chromosome 22q
• Female sex: hormonal influence (some meningiomas express progesterone receptors)
• Obesity: higher BMI associated with increased risk

Pathophysiology

Arises from arachnoid cap cells in the meninges. Extra-axial (outside brain parenchyma), well-circumscribed, often with a broad dural base. Growth is typically slow (1-2 mm/year for grade 1). Symptoms result from compression of adjacent brain, cranial nerves, or venous sinuses rather than invasion. WHO grade 2 and 3 meningiomas have higher mitotic activity and risk of recurrence/brain invasion.

Common Presentations

• Incidental finding: many discovered on imaging for other reasons
• Headache: compression/traction; may mimic raised ICP
• Seizures: cortical irritation (convexity meningiomas)
• Focal neurological deficit: depends on location

Location-Specific

• Parasagittal/falcine: seizures, leg weakness (motor cortex)
• Convexity: seizures, focal deficit based on cortex involved
• Sphenoid wing: temporal lobe compression, proptosis, visual field deficit
• Olfactory groove: anosmia, personality change (Foster Kennedy syndrome — ipsilateral optic atrophy + contralateral papilloedema)
• Cerebellopontine angle: hearing loss, facial numbness, ataxia
• Tuberculum sellae/suprasellar: visual field defect (bitemporal hemianopia)
• Spinal: cord compression

Red Flags

• Progressive neurological deficit → active tumour growth
• Seizures → cortical involvement
• Rapid growth → consider higher grade (atypical/malignant)

Imaging

• MRI brain with gadolinium: gold standard; well-defined, dural-based, homogeneous enhancement, dural tail sign, may have calcification
• CT head: may show calcification, hyperostosis of adjacent bone, homogeneous enhancement
• MR angiography/venography: if adjacent to major venous sinuses (sagittal sinus, cavernous sinus)

Pre-Operative

• Digital subtraction angiography (DSA): for large tumours; may allow pre-operative embolisation of feeding vessels
• MR perfusion/spectroscopy: may help differentiate from other dural lesions

Histopathology

• WHO grading: grade 1 (mitoses <4/10 HPF), grade 2 (4-19/10 HPF or brain invasion), grade 3 (≥20/10 HPF)
• Molecular: TERT promoter mutation (associated with higher grade/recurrence)

Monitoring

• Serial MRI (6-monthly then annual) for observation strategy

Observation (Watch-and-Wait)

• Small (<3 cm), asymptomatic, incidental meningiomas
• Serial MRI: 6 months, 1 year, then annually if stable
• ~60-70% of incidental meningiomas show no significant growth over 5 years

Surgical Resection

• Indications: symptomatic, growing on serial imaging, significant mass effect
• Simpson grading of resection completeness: grade I (complete removal + dural excision + bone) — lowest recurrence; grade V (biopsy only)
• Curative for most WHO grade 1 if Simpson grade I resection

Radiotherapy

• Stereotactic radiosurgery (SRS — Gamma Knife/CyberKnife): for small (<3 cm) tumours; residual/recurrent after surgery; surgically inaccessible (cavernous sinus, skull base); ~95% local control at 10 years
• Fractionated RT: for larger tumours or when SRS not feasible
• Adjuvant RT: recommended for WHO grade 2/3 after subtotal resection

Pharmacological

• Limited role; no effective chemotherapy for most meningiomas
• Anti-progesterone agents (mifepristone): limited evidence, not standard

Referral Criteria

• Neurosurgical MDT: all symptomatic or growing meningiomas
• Serial MRI surveillance for incidental lesions

WHO grade 1: 10-year recurrence ~10% after gross total resection; near-normal life expectancy. WHO grade 2 (atypical): 10-year recurrence ~40%; benefits from adjuvant RT after subtotal resection. WHO grade 3 (malignant): aggressive; median survival ~2-5 years; high recurrence rate. SRS for residual/recurrent grade 1: >90% local control at 10 years. Observation: ~60-70% of incidental meningiomas remain stable or grow minimally over 5 years.

Simpson Grading of Meningioma Resection

Common Meningioma Locations