Meningioma

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1. Overview

Meningiomas are the most common primary intracranial tumour in adults, accounting for approximately 37-39% of all primary brain tumours. [1,2] They originate from the arachnoid cap cells of the meninges (the protective membranes covering the brain and spinal cord), not from brain tissue itself.

The vast majority of meningiomas are benign (WHO Grade 1), slow-growing, and extra-axial (arising outside the brain parenchyma). They typically compress rather than invade the adjacent brain tissue, which has important implications for surgical management and prognosis. [3]

While most meningiomas are discovered incidentally or present with slowly progressive symptoms, approximately 5-7% are atypical (WHO Grade 2) and 1-3% are anaplastic/malignant (WHO Grade 3), with significantly higher rates of recurrence and poorer outcomes. [4,5] Modern molecular classification has refined our understanding of prognosis beyond histological grading alone. [7]

Key Clinical Message: Most meningiomas can be managed conservatively with imaging surveillance if asymptomatic and small. For symptomatic lesions, the goal is maximal safe resection with preservation of neurological function. Stereotactic radiosurgery offers excellent control for small, surgically inaccessible tumours.

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2. Epidemiology

Incidence and Prevalence

Demographics and Risk Factors

Age: Incidence increases substantially with age, peaking in the seventh decade. Meningiomas are rare in children and young adults (unless associated with neurofibromatosis type 2). [2]

Sex: Meningiomas show a strong female predominance (F:M ratio 2.3:1), attributed to the presence of hormone receptors (progesterone and estrogen) in many tumours. [1,2] This ratio is even higher for spinal meningiomas (approximately 4:1).

Race/Ethnicity: Higher incidence rates are observed in Black populations compared to White populations in the United States. [2]

Risk Factors:

1. Ionizing Radiation: Well-established risk factor. Meningiomas can develop 10-30 years after cranial irradiation (e.g., childhood leukaemia treatment, prophylactic cranial irradiation). [1]
2. Neurofibromatosis Type 2 (NF2): Germline mutations in the NF2 gene (chromosome 22q12) predispose to multiple meningiomas, typically presenting at younger ages. [8]
3. Hormonal Factors:
   • Pregnancy can accelerate meningioma growth (progesterone receptor-positive tumours). [1]
   • Hormone replacement therapy (HRT) shows weak association with increased risk. [1]
   • Oral contraceptives have inconsistent evidence for increased risk. [1]
4. Obesity and Metabolic Syndrome: Emerging evidence suggests association with increased risk. [1]
5. Prior head trauma: Weak and inconsistent evidence. [1]

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3. Aetiology & Pathophysiology

Cellular Origin

Meningiomas arise from arachnoid cap cells, which are specialized meningothelial cells forming the outer layer of the arachnoid membrane. These cells are found predominantly at arachnoid villi (sites where CSF is reabsorbed into venous sinuses), explaining the predilection for parasagittal and convexity locations. [1]

Molecular Pathogenesis

Exam Detail: NF2/Merlin Pathway (Chromosome 22q12):

• NF2 gene encodes merlin (schwannomin), a tumour suppressor protein. [8]
• Loss of NF2 function is the most common molecular alteration in meningiomas, occurring in 40-60% of all grades. [7,8]
• NF2 loss is associated with higher-grade tumours and poorer prognosis. [7]
• Merlin regulates cell proliferation, adhesion, and contact inhibition through interactions with cytoskeletal proteins and receptor tyrosine kinases. [8]

Non-NF2 Molecular Subtypes:

Recent integrative molecular classification identifies distinct biological groups: [7]

1. Merlin-intact, Immunogenic: Characterized by immune-enriched microenvironment, better prognosis.
2. Merlin-intact, Hypermetabolic: Activated PI3K/AKT signalling, intermediate prognosis.
3. Merlin-deficient, Proliferative: NF2 loss with high proliferation markers, worse prognosis.

Additional Key Alterations:

• TRAF7 mutations: Often co-occur with AKT1 or KLF4 mutations, typically WHO Grade I, excellent prognosis. [7]
• AKT1 E17K mutation: Activating mutation in PI3K/AKT pathway, associated with meningothelial histology and skull base location. [7]
• SMO mutations: Associated with medial skull base meningiomas. [7]
• CDKN2A/B homozygous deletion: Associated with Grade 3 tumours and very poor prognosis. [4,7]
• TERT promoter mutations: Marker of aggressive behaviour and shortened recurrence-free survival. [4,7]
• BAP1 mutations: Associated with high-grade, aggressive meningiomas, particularly rhabdoid subtype. [4]

DNA Methylation Classification:

DNA methylation profiling provides prognostic information beyond histological grade, identifying three methylation classes with distinct clinical outcomes: [5]

• Benign: Best prognosis
• Intermediate: Moderate risk of recurrence
• Malignant: High risk of recurrence, regardless of histological grade

Growth Pattern and Local Effects

1. Expansile Growth: Meningiomas grow slowly by mass effect, compressing and displacing adjacent brain parenchyma rather than infiltrating it (except in malignant variants). [1]

2. Dural Attachment: Strong attachment to dura mater with broad dural base. Tumour cells infiltrate dura and stimulate dural hypervascularity. [1]

3. Bone Involvement:

   • Hyperostosis: Thickening of adjacent skull bone (most common, seen in 20-40%). [1]
   • Osteolysis: Bone erosion/destruction (less common, more concerning for malignancy). [1]

4. Vascular Supply: Primarily from dural blood vessels (external carotid branches: middle meningeal, accessory meningeal, occipital arteries). Larger tumours may recruit pial blood supply. [1]

5. Venous Sinus Invasion: Parasagittal meningiomas can invade or encase the superior sagittal sinus (SSS), making complete resection hazardous. [1]

Histopathology

WHO Grade I (Benign): Nine histological subtypes including:

• Meningothelial: Lobular architecture, syncytial sheets
• Fibrous: Fascicles of spindle cells with abundant collagen
• Transitional (Mixed): Features of both meningothelial and fibrous
• Psammomatous: Abundant psammoma bodies (concentric calcified whorls)
• Others: angiomatous, microcystic, secretory, lymphoplasmacyte-rich, metaplastic [6]

WHO Grade II (Atypical): Defined by increased mitotic activity (≥4 mitoses per 10 high-power fields) OR ≥3 of the following: increased cellularity, small cells, prominent nucleoli, uninterrupted patternless/sheet-like growth, necrosis. Also includes brain invasion, chordoid and clear cell subtypes. [4,6]

WHO Grade III (Anaplastic/Malignant): ≥20 mitoses per 10 high-power fields OR frank anaplasia/carcinoma-like features. Also includes papillary and rhabdoid subtypes. [4,6]

Classic Histological Features:

• Whorled architecture: Concentric arrangement of meningothelial cells
• Psammoma bodies: Laminated calcospherites (calcified necrotic cells)
• Nuclear pseudoinclusions: Invagination of cytoplasm into nucleus
• EMA positivity: Immunohistochemistry marker (epithelial membrane antigen)

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4. Clinical Presentation

Clinical manifestations depend on location, size, growth rate, and surrounding structures affected. Many meningiomas (up to 50%) are asymptomatic "incidentalomas" discovered on imaging for unrelated reasons. [1,19]

General Symptoms

Headache (30-50% of symptomatic patients)

• Typically insidious, progressively worsening
• Worse in morning or with Valsalva (suggests raised ICP)
• Often localized to tumour location but can be diffuse [1]

Seizures (20-40% at presentation)

• Due to cortical irritation from compression or oedema
• Can be focal or generalized
• More common with convexity tumours
• May be first presenting symptom in otherwise asymptomatic patients [1,19]

Cognitive and Personality Changes

• Subtle cognitive decline, memory impairment
• Personality changes, apathy, disinhibition (frontal lobe compression)
• Often noticed by family members before patient [1]

Raised Intracranial Pressure

• Morning headache with nausea/vomiting
• Papilloedema on fundoscopy
• Visual obscurations (transient vision loss)
• Sixth nerve palsy (false localizing sign)
• Advanced: altered consciousness, Cushing's triad [1]

Location-Specific Syndromes

Atypical and High-Grade Features

Features suggesting WHO Grade II/III:

• Rapid symptom progression (weeks to months rather than years)
• Significant peritumoral oedema out of proportion to tumour size
• Younger age (\u003c40 years) without NF2
• Aggressive bone destruction (osteolysis)
• Evidence of brain invasion on imaging [4,14]

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5. Clinical Examination

Systematic Neurological Examination

1. Mental State and Higher Functions

• Cognitive screening (e.g., MMSE, Montreal Cognitive Assessment)
• Frontal lobe assessment: verbal fluency, proverb interpretation, go/no-go tasks
• Personality and behavioural changes (collateral history)

2. Cranial Nerves (I-XII)

• CN I: Formal olfaction testing (may reveal early olfactory groove lesions)
• CN II:
  • Visual acuity (Snellen chart)
  • "Fundoscopy: Papilloedema (raised ICP) vs optic atrophy (chronic compression)"
  • "Visual fields: confrontation and formal perimetry (bitemporal hemianopia = suprasellar)"
• CN III, IV, VI: External ophthalmoplegia, ptosis, pupil responses (cavernous sinus involvement)
• CN V: Facial sensation (V1/V2/V3 distribution), corneal reflex, masseter bulk
• CN VII: Facial weakness (differentiate UMN vs LMN pattern)
• CN VIII: Hearing loss, tinnitus (cerebellopontine angle meningioma)
• CN IX, X: Palatal movement, gag reflex, dysphonia (posterior fossa/foramen magnum)
• CN XI: Sternocleidomastoid and trapezius strength
• CN XII: Tongue deviation, fasciculations

3. Motor System

• Inspection: wasting, fasciculations
• Tone: spasticity (UMN), rigidity
• Power: MRC grade 0-5 (upper and lower limbs)
• Pattern recognition:
  • Hemiparesis = contralateral hemisphere
  • Leg weakness \u003e arm = parasagittal/falx
  • Quadriparesis = foramen magnum or bilateral hemispheric

4. Reflexes

• Deep tendon reflexes: symmetry, hyperreflexia
• Plantar responses: Extensor (Babinski sign) = UMN lesion
• Primitive reflexes (grasp, palmomental) = frontal lobe dysfunction

5. Sensory System

• Cortical sensation: stereognosis, graphesthesia, two-point discrimination
• Spinothalamic: pain, temperature (crossed findings = brainstem)
• Dorsal column: vibration, proprioception (may be affected in spinal meningiomas)

6. Cerebellar Function

• Finger-nose test, heel-shin test
• Dysdiadochokinesia
• Gait: ataxia, tandem walking (posterior fossa lesions)

7. Gait and Stance

• Hemiplegic gait, apraxic gait (frontal lesions)
• Ataxic gait (cerebellar)
• Spastic paraparesis (spinal cord compression)

8. Signs of Raised ICP

• Papilloedema (gold standard)
• Sixth nerve palsy (false localizing)
• Altered consciousness (late)
• Cushing's triad: hypertension, bradycardia, irregular respirations (preterminal)

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6. Differential Diagnosis

Extra-Axial (Dural-Based) Lesions

Cerebellopontine Angle (CPA) Lesions

Intra-Axial Mimics (Less Common)

• Glioblastoma: Intra-axial, irregular enhancement, necrosis, vasogenic oedema, rapid progression
• CNS Lymphoma: Deep periventricular location, homogeneous enhancement, immunocompromised

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7. Investigations

First-Line Imaging

1. MRI Brain with Gadolinium Contrast (Gold Standard)

Rationale: Superior soft tissue resolution; multiplanar capability; definitive for diagnosis and surgical planning. [9,19]

Classical Features:

• Extra-axial location: "CSF cleft" sign - thin CSF space between tumour and brain parenchyma
• Dural tail sign: Linear dural enhancement extending from tumour margin (60-72% sensitive, not 100% specific - also seen in metastases, lymphoma, sarcoidosis) [9,10]
• Broad dural base: Wide attachment to dura
• Intense homogeneous enhancement: "Vivid" enhancement with gadolinium (highly vascular)
• Displacement of grey-white matter junction: Confirms extra-axial origin
• "White matter buckling": Compressed white matter tracts bow away from tumour

T1-weighted:

• Isointense to hypointense relative to grey matter
• Post-contrast: intense, homogeneous enhancement

T2-weighted:

• Variable signal (isointense to hyperintense)
• Peritumoral oedema (vasogenic pattern - hyperintense, finger-like projections along white matter)

FLAIR:

• Hyperintense tumour
• Oedema very conspicuous (high signal)

DWI (Diffusion-Weighted Imaging):

• Typically restricted diffusion (dense cellular tumour)
• Helps differentiate from epidermoid cysts (which are also T2 hyperintense but show marked restricted diffusion)

Special Sequences for Surgical Planning:

• MR Venography (MRV): Assess venous sinus patency and invasion
• DTI (Diffusion Tensor Imaging): Visualize relationship to white matter tracts
• MR Angiography: Identify arterial feeders

Grading Prediction on MRI: [19]

• Heterogeneous enhancement, irregular margins, marked oedema, bone invasion, mushroom shape, adjacent brain invasion → suspect higher grade

2. CT Head (Non-Contrast and Contrast)

Advantages: Bone detail superior to MRI; faster; useful if MRI contraindicated.

Findings:

• Calcification: 20-25% of meningiomas (psammomatous type)
• Hyperostosis: Thickening of adjacent skull (highly suggestive of meningioma)
• Osteolysis: Bone destruction (raises concern for malignancy or metastasis)
• Hyperdense mass: 60-90% are hyperdense on non-contrast CT
• Homogeneous enhancement: Post-contrast

Role: Skull base lesions (bone involvement), preoperative assessment of hyperostosis, rapid evaluation in emergency.

Second-Line and Specialized Investigations

3. Catheter Angiography (DSA - Digital Subtraction Angiography)

Indications:

• Preoperative planning for large, vascular tumours
• Facilitates preoperative embolization

Findings:

• Tumour blush (hypervascular staining)
• Arterial supply typically from external carotid branches (middle meningeal artery most common)
• Venous sinus involvement/occlusion

Preoperative Embolization: [19]

• Reduces intraoperative blood loss (especially for large tumours \u003e5cm)
• Performed 24-72 hours before surgery
• Contraindicated if arterial supply also feeds eloquent brain or cranial nerves
• Not routinely performed for small/moderate tumours

4. MR Spectroscopy

Findings:

• Elevated alanine (most specific)
• Elevated choline (cell membrane turnover)
• Reduced NAA (N-acetyl aspartate) - not neuronal tissue
• Absent lactate (distinguishes from high-grade gliomas)

Utility: Limited; mainly research; may help differentiate meningioma from intra-axial glioma in equivocal cases.

5. PET Scan

Indications: Rarely used; may differentiate benign from malignant if histology uncertain.

Findings: FDG-PET uptake correlates with WHO grade (higher uptake in Grade II/III).

Histopathology and Molecular Testing

6. Tissue Diagnosis

Indications:

• Confirm diagnosis (vs metastasis, lymphoma, inflammatory)
• WHO grading (I, II, III)
• Molecular profiling to guide prognosis and adjuvant therapy

Methods:

• Surgical resection: Provides definitive diagnosis + treatment
• Stereotactic biopsy: Rarely needed (imaging usually diagnostic); reserved for atypical presentations or inaccessible lesions being considered for radiotherapy without surgery

Key Histological Assessment: [4,6]

• Mitotic count per 10 high-power fields
• Brain invasion (upgrades to WHO Grade II minimum)
• Presence of necrosis, hypercellularity, nuclear atypia
• Subtype (meningothelial, fibrous, transitional, etc.)

Immunohistochemistry:

• EMA (Epithelial Membrane Antigen): Positive in meningiomas
• Progesterone receptor (PR): Positive in 60-80% (WHO Grade I); loss associated with higher grade
• Ki-67 (MIB-1) labeling index: Proliferation marker (\u003c3% typical for Grade I; \u003e5% suggests Grade II; \u003e15% suggests Grade III)

7. Molecular Testing [4,5,7]

Increasingly Important for Prognosis:

DNA Methylation Profiling: [5]

• Classifies meningiomas into benign, intermediate, or malignant methylation classes
• Provides prognostic information independent of histological grade
• Not yet universally available

Targeted Gene Sequencing:

• NF2 status (chromosome 22q loss or mutation)
• TERT promoter mutations: Associated with worse prognosis, higher recurrence
• CDKN2A/B homozygous deletion: Very poor prognosis; consider intensified treatment
• BAP1 mutations: Rhabdoid meningiomas; aggressive

Cytogenetics:

• Monosomy 22 (NF2 region)
• Additional losses: chromosomes 1p, 6q, 10, 14q (associated with higher grade and recurrence)

Clinical Utility: [13,14]

• Risk stratification beyond WHO grade
• Identify patients who may benefit from adjuvant radiotherapy despite WHO Grade I histology
• Future: targeted therapies based on molecular profile

Laboratory Investigations

• Routine bloods: FBC, U&E, clotting (preoperative)
• Hormone profile: If suprasellar location (pituitary axis assessment)
• Tumour markers: NOT useful (meningiomas do not secrete markers)
• Genetic counselling/testing: If multiple meningiomas or young age (\u003c40) → consider NF2 genetic testing

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8. Classification & Grading

WHO Grading (2021 Classification) [4,6]

Key Points:

• Brain invasion alone is sufficient to diagnose WHO Grade II (even with low mitotic count). [4,6]
• Mitotic count is the most objective criterion.
• Progesterone receptor loss and elevated Ki-67 (\u003e5%) support higher grade but are not diagnostic criteria.

Simpson Grading System (Extent of Resection) [12]

Developed in 1957 by Sir Donald Simpson; predicts recurrence based on completeness of resection.

Modern Perspective: [12]

• Simpson Grade remains valid and widely used.
• Caveats: Developed in pre-MRI era; did not account for WHO grade or molecular factors.
• Goal: Achieve Simpson I or II when safely possible.
• Adjuvant radiotherapy can compensate for Simpson IV resection in selected cases.
• Molecular risk stratification may be more predictive than Simpson grade alone for high-risk tumours. [13]

Anatomical Location Classification [1,19,24,25]

Molecular Classification [7]

Emerging Standard (not yet routine clinical practice):

Three major molecular groups with prognostic implications:

1. Merlin-intact, Immunogenic

   • Immune-enriched tumour microenvironment
   • Better overall survival
   • May respond to immune checkpoint inhibitors (investigational)

2. Merlin-intact, Hypermetabolic

   • Activated metabolic pathways (PI3K/AKT)
   • Intermediate prognosis

3. Merlin-deficient, Proliferative

   • NF2 loss + high proliferation
   • Worse progression-free survival
   • May benefit from targeted therapies (SMO inhibitors, FAK inhibitors - under investigation)

Special Molecular Markers:

• CDKN2A/B homozygous deletion: Reclassified as CNS WHO Grade 3 regardless of histology (cIMPACT-NOW update 8). [4]
• TERT promoter mutation: Confers Grade 3 behaviour even in otherwise Grade 1/2 histology. [4]

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9. Management

Management depends on size, location, symptoms, WHO grade, patient age/comorbidity, and growth rate. [19]

A. Conservative Management ("Watch and Wait")

Indications

• Asymptomatic, incidentally discovered meningiomas
• Small size (\u003c2.5-3cm diameter) [19]
• Elderly patients (limited life expectancy)
• Significant medical comorbidities prohibiting surgery
• Surgically inaccessible location with no mass effect

Protocol [19]

• Baseline MRI: Establishes size, location, characteristics
• Follow-up MRI:
  • 6 months after initial diagnosis
  • Then annually if stable
  • "If growth documented: repeat MRI in 3-6 months to confirm; consider intervention"
• Growth Rate: Average 2-4mm/year for WHO Grade I; higher for Grade II/III
• Conversion to Surgery: 10-20% of observed patients eventually require treatment

Evidence Base

• Many meningiomas remain stable for years or grow very slowly. [19]
• Observation is safe in selected patients with low-risk features.
• Quality of life often preserved vs surgical morbidity in asymptomatic elderly patients.

Patient Counselling: Explain natural history, symptoms to watch for (new headaches, seizures, focal weakness), need for regular imaging compliance.

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B. Surgical Resection

Indications [19]

• Symptomatic meningiomas (headaches, seizures, focal deficits)
• Growing tumours (even if asymptomatic)
• Significant oedema or mass effect
• Size \u003e3cm (increased risk of symptoms)
• Young patients (life expectancy \u003e10 years)
• Accessible location (convexity, parasagittal without major sinus involvement)

Preoperative Preparation

1. Imaging review: MRI + MRV (assess sinus patency); consider angiography for large tumours
2. Preoperative embolization: For large, hypervascular tumours (\u003e5cm), 24-72 hours preoperatively [19]
3. Anticonvulsants: Controversial; consider if seizure history or high-risk location (motor cortex)
4. Corticosteroids: Dexamethasone if significant oedema (reduce perioperative brain swelling)
5. DVT prophylaxis: Sequential compression devices, early mobilization

Surgical Goals [12,14]

• Maximal safe resection: Aim for Simpson Grade I or II
• Preservation of neurological function: Eloquent cortex, cranial nerves, vascular structures
• Resection of involved dura: Reduce recurrence
• Resection/drilling of hyperostotic bone: Remove invaded bone

Surgical Approaches (Location-Dependent)

Intraoperative Techniques

• Internal debulking: Hollowing out tumour before capsular dissection (reduces mass, tension)
• Piecemeal removal: Safer than en bloc for vascular adherence
• Coagulation/excision of dural base: Simpson I (excise) or II (coagulate)
• Neuronavigation: Frameless stereotaxy for surgical planning and orientation
• Neurophysiological monitoring: SSEPs, MEPs (motor pathways); CN monitoring (VII, VIII for CPA)
• Intraoperative imaging: Intraoperative MRI or ultrasound to confirm extent of resection

Postoperative Care

• ICU/HDU monitoring: First 24 hours (neurological observations)
• Imaging: CT head within 24 hours to exclude haematoma
• Dexamethasone taper: Over 5-7 days
• VTE prophylaxis: LMWH + compression stockings
• Antiepileptics: Continue if preoperative seizures; consider for perilesional irritation
• Follow-up MRI: 3 months postoperatively (baseline); then annually

Surgical Outcomes [14]

• Mortality: \u003c2% for convexity; up to 5-10% for complex skull base
• Morbidity: Depends on location
  • "Convexity: 5-10% (hemiparesis, seizures, infection)"
  • "Skull base: 20-40% (cranial nerve palsies, CSF leak, stroke)"
• Simpson I/II resection: Achievable in 70-90% of convexity tumours; 30-50% of skull base
• Recurrence (Simpson I, WHO Grade I): ~10% at 10 years

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C. Stereotactic Radiosurgery (SRS)

High-precision, single-session (or hypofractionated) radiation delivery.

Indications [15,16,19]

1. Primary Treatment:

   • Small tumours (\u003c3cm diameter, \u003c10-15cc volume)
   • Surgically inaccessible locations (cavernous sinus, petroclival, optic nerve sheath)
   • Medical comorbidities prohibiting surgery
   • Patient preference

2. Adjuvant Treatment:

   • Residual tumour after subtotal resection (Simpson III/IV)
   • Recurrent meningioma after prior surgery
   • WHO Grade II/III meningiomas with residual disease

3. Special Cases:

   • NF2-associated meningiomas (multiple lesions) [17]
   • Elderly/frail patients

Technologies

• Gamma Knife: Cobalt-60 sources; most data available; excellent for skull base
• Linear Accelerator (LINAC)-based: CyberKnife, Novalis, TrueBeam
• Proton Beam: Emerging; potential benefit for optic apparatus tumours (sharper dose fall-off)

Dosing [15,16,18]

• Typical Prescription Dose: 12-14 Gy to tumour margin (single session)
• Fractionated SRS (3-5 fractions): For tumours near optic apparatus or brainstem (to reduce toxicity)
  • "Example: 25 Gy in 5 fractions"
• Critical Structure Constraints: [18]
  • "Optic nerves/chiasm: Max 8-10 Gy (single session); \u003c25 Gy (fractionated)"
  • "Brainstem: Max 12-15 Gy (single session)"

Outcomes [15,16,19]

• Tumour Control: 90-95% at 5 years; 85-90% at 10 years
• Progression-Free Survival: Higher for WHO Grade I vs Grade II/III
• Volumetric Response:
  • "Decrease: 30-50%"
  • "Stable: 40-60%"
  • "Growth: 5-10%"
• Timing of Response: Slow; may take 1-2 years to see shrinkage
• Complications:
  • "Radiation-induced oedema: 5-10% (transient; steroid-responsive)"
  • "Cranial neuropathy: 2-5% (depends on dose to nerves)"
  • "Radiation necrosis: \u003c1%"
  • "Malignant transformation: Exceedingly rare (\u003c0.1%)"

Limitations

• Size: \u003e3cm diameter or \u003e15cc volume → less effective, higher toxicity
• Proximity to optic apparatus: Dose constraints may limit efficacy
• High-grade meningiomas (WHO III): Higher failure rates; consider surgery + fractionated RT instead

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D. Fractionated External Beam Radiotherapy (EBRT)

Conventional radiotherapy delivered over multiple sessions (fractions).

Indications [19,20,21]

1. Adjuvant after surgery:
   • WHO Grade II (Atypical): After Simpson IV resection or recurrence
   • WHO Grade III (Anaplastic): After any resection (even GTR) - high recurrence risk
2. Definitive treatment (no surgery):
   • Inoperable tumours (medically unfit, eloquent location)
   • Extensive skull base involvement
3. Recurrent disease: After prior surgery ± SRS failure

Dosing [20,21]

• Standard Dose: 54-60 Gy in 1.8-2 Gy fractions (over 6 weeks)
• Planning: CT/MRI fusion; IMRT (intensity-modulated RT) for skull base to spare critical structures
• Target Volume: Gross tumour + margin (typically 1-2cm for Grade I; 2cm for Grade II/III)

Outcomes [20,21]

• WHO Grade I: 5-year local control 90-95%
• WHO Grade II: 5-year local control 70-80%; recurrence risk ~30-50%
• WHO Grade III: 5-year local control 40-60%; median survival 5-7 years despite aggressive treatment
• NRG Oncology/RTOG 0539 Trial (High-Risk Meningiomas): [21]
  • "Grade II + GTR: Observation vs adjuvant RT - outcomes similar if GTR achieved"
  • "Grade II + STR or Grade III: Adjuvant RT improves outcomes"
  • "Dose: 54 Gy (low risk) vs 60 Gy (high risk)"

Complications

• Acute: Fatigue, alopecia, skin erythema, headache
• Delayed: Radiation necrosis (rare \u003c5%), neurocognitive decline (particularly whole-brain RT, not used for meningioma), hypopituitarism (skull base RT), optic neuropathy (dose-dependent), secondary malignancy (very rare, latency 10-20 years)

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E. Systemic Therapy (Medical Treatment)

Limited role; reserved for refractory, recurrent, or unresectable high-grade meningiomas.

Hormonal Therapy

• Rationale: Progesterone/estrogen receptors present in many meningiomas
• Agents Tried: Mifepristone (progesterone antagonist), tamoxifen, hydroxyurea
• Evidence: Disappointing; no consistent benefit in clinical trials
• Current Role: Not recommended [19]

Chemotherapy

• Traditional cytotoxics: Ineffective for meningiomas (temozolomide, irinotecan, cyclophosphamide trials failed)
• Current Role: None

Targeted Molecular Therapies (Investigational)

• SMO Inhibitors (e.g., vismodegib): For SMO-mutant meningiomas (rare)
• FAK Inhibitors (e.g., defactinib): Merlin-deficient meningiomas (Phase II trials ongoing)
• VEGF Inhibitors (e.g., bevacizumab): Anecdotal responses in recurrent high-grade; not proven
• mTOR Inhibitors (e.g., everolimus): Minimal benefit

Immune Checkpoint Inhibitors

• Rationale: Some meningiomas have immune-enriched microenvironment [7]
• Agents: Pembrolizumab (anti-PD-1), nivolumab
• Evidence: Case reports of responses; clinical trials ongoing
• Current Role: Investigational only

Bottom Line: Systemic therapies NOT standard of care; consider clinical trial enrollment for refractory cases.

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F. Management Algorithm (Summary)

Suspected Meningioma
         |
         v
   MRI Brain + Contrast
         |
         v
Confirmed Extra-axial Dural-Based Mass
         |
         +---------------------------------+
         |                                 |
  ASYMPTOMATIC                       SYMPTOMATIC
  Small (\u003c3cm)                       OR Growing
  Elderly/Comorbid                    OR Large
         |                                 |
         v                                 v
  OBSERVATION                         ASSESSMENT
  (MRI 6mo, then                      (Age, Location,
   annually)                           Surgical Risk)
                                            |
                    +-----------------------+-----------------------+
                    |                       |                       |
              SURGERY SUITABLE        SURGERY HIGH RISK        INOPERABLE
              (Convexity,             (Skull Base,             (Extensive,
               Accessible,             Cavernous Sinus,         Comorbid)
               Young/Fit)              Elderly)                      |
                    |                       |                       v
                    v                       v                  RADIOSURGERY
            CRANIOTOMY +              RADIOSURGERY              (if \u003c3cm)
            RESECTION                 (if \u003c3cm)                   OR
            (Simpson I/II)            OR                       EBRT
                    |                 SURGERY + SRS             (if \u003e3cm)
                    v                 for residual
            HISTOPATHOLOGY                  |
            + MOLECULAR                     v
                    |                  HISTOPATHOLOGY
         +----------+----------+            (if resected)
         |          |          |
    WHO Grade I  Grade II   Grade III
         |          |          |
    Simpson I/II   |          |
         |          v          v
         v      Simpson I/II: Observe    ADJUVANT EBRT
    OBSERVE     Simpson III/IV: Adjuvant (even if GTR)
    (MRI annually) RT OR Observe        (54-60 Gy)
                    |
              MRI 3-monthly
              (high recurrence risk)

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10. Complications

Surgical Complications

Radiosurgery/Radiotherapy Complications

Disease-Related Complications

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11. Prognosis & Outcomes

Survival by WHO Grade [1,2,19,21]

Recurrence Rates [12,19,21]

Influenced by:

1. WHO Grade: Grade I \u003c\u003c Grade II \u003c Grade III
2. Extent of Resection (Simpson Grade): I \u003c II \u003c III \u003c IV
3. Molecular Markers: CDKN2A/B deletion, TERT promoter mutation (higher recurrence)

Time to Recurrence:

• WHO Grade I: Median 5-7 years (can be \u003e10 years)
• WHO Grade II: Median 3-5 years
• WHO Grade III: Median 1-3 years

Functional Outcomes

Post-Surgical Neurological Outcomes: [14]

• Convexity meningiomas: 80-90% maintain or improve functional status (Karnofsky \u003e80)
• Skull base meningiomas: 60-70% maintain baseline function; cranial nerve deficits in 10-40%
• Foramen magnum: High morbidity (quadriparesis risk); 70-80% ambulate independently postop if operated early

Seizure Outcomes:

• 60-80% of patients with preoperative seizures become seizure-free after tumour resection
• 10-15% develop new-onset postoperative seizures (usually transient)

Quality of Life:

• Most patients with WHO Grade I tumours after successful resection report good QoL
• Cognitive dysfunction, personality change may persist if frontal lobe injury occurred
• Skull base surgery morbidity (diplopia, facial numbness) impacts QoL

Prognostic Factors (Multivariate Analysis)

Favourable Prognostic Factors:

• WHO Grade I histology
• Complete resection (Simpson I/II)
• Younger age (\u003c60 years)
• Convexity location (vs skull base)
• Absence of brain invasion
• Low Ki-67 (\u003c3%)
• Favourable molecular profile (e.g., TRAF7/AKT1 mutations)

Adverse Prognostic Factors:

• WHO Grade II/III
• Subtotal resection (Simpson III/IV)
• Elderly age (\u003e70 years)
• Skull base location
• Brain invasion
• High Ki-67 (\u003e15%)
• NF2 loss
• CDKN2A/B homozygous deletion [4]
• TERT promoter mutation [4]

Natural History (Untreated)

• Small, asymptomatic meningiomas: ~40% remain stable over 5 years; ~50% grow slowly (2-4mm/year); ~10% grow rapidly (\u003e5mm/year requiring intervention)
• Mean growth rate: 2.4 mm/year (range 0-10 mm/year) [19]
• Predictors of growth: Younger age, male sex, oedema on baseline MRI, higher T2 signal

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12. Prevention & Screening

Primary Prevention

Avoid Ionizing Radiation:

• No unnecessary cranial CT scans (particularly in children)
• Justified use of radiation therapy (benefits outweigh late meningioma risk)
• Dental X-rays: Modern techniques use minimal radiation; risk negligible

Hormonal Considerations:

• Avoid unnecessary long-term HRT
• Oral contraceptives: Risk-benefit discussion (weak association)

No Proven Role for:

• Dietary interventions
• Lifestyle modifications

Screening

No Population-Based Screening (meningiomas are too rare to justify)

Targeted Surveillance:

1. Neurofibromatosis Type 2 (NF2):

   • Annual brain MRI starting at age 10-12 years (or younger if symptomatic)
   • Screen for multiple meningiomas, vestibular schwannomas, ependymomas
   • Genetic counselling for family members

2. Prior Cranial Irradiation:

   • Consider baseline MRI 10 years post-radiation
   • Low threshold for imaging if new symptoms
   • No formal guidelines exist

3. Incidental Meningioma Diagnosed:

   • Surveillance MRI protocol (6 months, then annually)
   • Patient education on symptoms to report

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13. Key Guidelines

European Association of Neuro-Oncology (EANO) Guidelines (2021) [19]

Key Recommendations:

1. Diagnosis: MRI with contrast is gold standard; histopathological diagnosis required for definitive management decisions.

2. Asymptomatic Meningiomas:

   • Small, incidental tumours: Observation with serial MRI acceptable (6 months, then annually).
   • Growth observed: Consider intervention.

3. Surgical Management:

   • Symptomatic meningiomas: Surgery is first-line if safely resectable.
   • Goal: Maximal safe resection (Simpson I/II).
   • Skull base tumours: Multidisciplinary decision (surgery vs radiosurgery vs observation).

4. Radiotherapy:

   • WHO Grade I:
     • Simpson I/II resection: Observation recommended.
     • Simpson IV resection: Consider adjuvant RT or observation (no consensus).
   • WHO Grade II:
     • Simpson I/II resection: Observation vs adjuvant RT (controversial; emerging evidence favours observation if GTR achieved).
     • Simpson III/IV resection: Adjuvant RT recommended.
     • Recurrent: RT recommended.
   • WHO Grade III:
     • Adjuvant RT recommended after any resection.
     • Dose: 60 Gy in 2 Gy fractions.

5. Stereotactic Radiosurgery:

   • Tumours \u003c3cm, \u003e5mm from optic apparatus: SRS is effective primary or adjuvant treatment.
   • Cavernous sinus, petroclival: SRS often preferred over high-risk surgery.

6. Systemic Therapy:

   • No standard effective systemic therapy.
   • Clinical trial enrollment recommended for refractory high-grade meningiomas.

7. Follow-Up:

   • MRI at 3 months postoperatively, then annually for Grade I; every 6 months for Grade II/III.
   • Long-term surveillance required (recurrence can occur \u003e10 years).

Other Relevant Guidelines

• Congress of Neurological Surgeons (CNS) Guidelines (2016): Similar recommendations to EANO; emphasis on Simpson grading and role of adjuvant RT for high-grade meningiomas.
• National Comprehensive Cancer Network (NCCN): Meningiomas included in CNS cancer guidelines; aligns with EANO.
• UK NICE Guidance: No specific meningioma guideline; general brain tumour pathway applies.

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14. Common Exam Questions

Typical FRCS / MRCS / FRACS Viva Questions

1. "A 60-year-old woman presents with gradually progressive headaches and a single seizure. MRI shows a 4cm extra-axial mass at the convexity with dural tail sign. How would you manage this patient?"

   Model Answer: "This is likely a meningioma based on the imaging features (extra-axial, dural tail). My approach would be:

   • Confirm diagnosis with detailed MRI including MRV to assess venous sinus involvement.
   • Given symptoms (headaches, seizure) and size (\u003e3cm), observation is not appropriate; surgical resection is indicated.
   • Discuss in neuro-oncology MDT; counsel patient regarding risks/benefits.
   • Plan craniotomy with aim for Simpson Grade I or II resection (complete tumour removal plus dural margin).
   • Start antiepileptic drug for perioperative seizure prophylaxis.
   • Postoperative: histopathology will guide prognosis and need for adjuvant treatment.
   • If WHO Grade I with Simpson I/II resection, annual MRI surveillance. If Grade II/III or subtotal resection, consider adjuvant radiotherapy per EANO guidelines."

2. "What is the Simpson Grading system and why is it important?"

   Model Answer: "The Simpson Grading system (1957) predicts recurrence risk based on extent of surgical resection. It has five grades:

   • Grade I: Complete tumour removal plus dural attachment and abnormal bone – lowest recurrence (~10% at 10 years).
   • Grade II: Complete tumour removal plus coagulation of dura – slightly higher recurrence (~20%).
   • Grade III: Complete tumour removal without dural treatment – not recommended.
   • Grade IV: Subtotal resection – high recurrence (~40%).
   • Grade V: Biopsy only.

   It's important because extent of resection is the strongest modifiable prognostic factor. However, modern practice recognizes that WHO grade, molecular markers, and location also influence recurrence, so Simpson grading should not be pursued at the expense of neurological function."

3. "What are the indications for stereotactic radiosurgery in meningioma?"

   Model Answer: "SRS is indicated in:

   • Primary treatment for small tumours (\u003c3cm) in surgically inaccessible locations (e.g., cavernous sinus, petroclival).
   • Adjuvant treatment for residual tumour after subtotal resection.
   • Recurrent meningiomas after prior surgery.
   • Patients unfit for surgery due to comorbidities.
   • Multiple meningiomas in NF2 patients.

   Typical dose is 12-14 Gy to the tumour margin. Outcomes show 90-95% tumour control at 5 years. Limitations include size (\u003e3cm less effective), proximity to optic apparatus (dose constraints), and higher failure rates for WHO Grade III tumours."

4. "Describe the typical MRI features of a meningioma."

   Model Answer: "Classic MRI features include:

   • Extra-axial location: CSF cleft between tumour and brain.
   • Dural tail sign: Linear dural enhancement extending from tumour margin (60-70% sensitive, not 100% specific).
   • Broad dural base: Wide attachment to dura.
   • Intense homogeneous enhancement with gadolinium.
   • T1: Isointense to hypointense.
   • T2: Variable (isointense to hyperintense).
   • Associated findings: hyperostosis (bone thickening), peritumoral oedema (vasogenic pattern), displacement of grey-white junction.

   Atypical features suggesting higher grade include heterogeneous enhancement, irregular margins, significant oedema, and brain invasion."

5. "What are the risk factors for meningioma?"

   Model Answer: "Key risk factors are:

   • Ionizing radiation: Well-established; latency 10-30 years post-exposure.
   • Neurofibromatosis Type 2: Germline NF2 mutation predisposes to multiple meningiomas at younger age.
   • Female sex: 2.3:1 female:male ratio, related to hormone receptor expression.
   • Hormonal factors: Pregnancy, HRT (weak association).
   • Age: Incidence increases with age, peak in 7th decade.

   Obesity and metabolic syndrome are emerging risk factors under investigation."

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15. Viva Scenario & Points

Viva Point: Opening Statement: "Meningioma is the most common primary intracranial tumour, accounting for approximately 37-39% of all primary CNS tumours. It arises from arachnoid cap cells of the meninges, is typically extra-axial, slow-growing, and benign (WHO Grade I) in 80-90% of cases. The hallmark imaging feature is the dural tail sign on contrast MRI. Management depends on size, location, symptoms, and patient factors, ranging from observation to surgical resection to stereotactic radiosurgery."

Key Facts for Viva:

1. Epidemiology: Incidence 8.8 per 100,000; F:M ratio 2.3:1; peak age 65-74 years. [2]

2. WHO Grading: Grade I (80-90%, benign), Grade II (5-7%, atypical, ≥4 mitoses/10 HPF or brain invasion), Grade III (1-3%, anaplastic, ≥20 mitoses/10 HPF). [4,6]

3. Molecular Classification: NF2 loss (40-60%), TRAF7/AKT1 mutations (good prognosis), CDKN2A/B deletion (poor prognosis, now considered Grade 3), TERT promoter mutation (aggressive). [4,7]

4. Simpson Grading: Grade I (tumour + dura + bone, 10% recurrence at 10y) \u003e Grade II (tumour + dura coagulation, 20%) \u003e Grade IV (subtotal, 40%). [12]

5. First-Line Investigation: MRI brain with gadolinium contrast. Features: dural tail, intense homogeneous enhancement, extra-axial location, CSF cleft. [9,19]

6. Management Principles:

   • Asymptomatic \u003c3 cm: Observation with MRI surveillance (6mo, then annually). [19]
   • Symptomatic/growing: Surgery (Simpson I/II) if accessible. [19]
   • Skull base \u003c3 cm: SRS (12-14 Gy, 90-95% control at 5y). [15,16]
   • WHO Grade II + GTR: Observation vs adjuvant RT (controversial). [21]
   • WHO Grade III: Adjuvant RT (60 Gy) recommended even after GTR. [21]

7. Prognosis:

   • WHO I: \u003e90% 10-year survival, 7-25% recurrence (depends on Simpson grade).
   • WHO II: 70-75% 10-year survival, 30-50% recurrence.
   • WHO III: 40-50% 10-year survival, 60-80% recurrence. [1,2,19,21]

8. EANO Guideline (2021): Surgery first-line for symptomatic resectable tumours; SRS for small skull base; adjuvant RT for Grade II after STR and all Grade III; observation acceptable for asymptomatic small tumours. [19]

Common Mistakes to Avoid:

• ❌ Assuming all dural tail signs are meningiomas (also seen in metastases, lymphoma, sarcoidosis).
• ❌ Not assessing venous sinus patency before parasagittal surgery (catastrophic if sinus patent and injured).
• ❌ Pursuing Simpson Grade I at expense of neurological function (balance complete resection with safety).
• ❌ Forgetting brain invasion automatically upgrades to WHO Grade II minimum.
• ❌ Not offering adjuvant RT for WHO Grade III even after gross total resection (recurrence rate remains high).

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16. Patient & Layperson Explanation

What is a Meningioma?

A meningioma is a type of brain tumour, but it's important to know that it doesn't actually grow from your brain cells. Instead, it grows from the meninges – the protective layers (like a thin wrapper) that cover your brain and spinal cord.

Is it Cancer?

Most meningiomas are NOT cancer. About 9 out of 10 meningiomas are benign, which means:

• They grow very slowly (over months to years)
• They do not spread to other parts of your body
• They can often be cured with treatment

A small number (about 1 in 10) are more aggressive and may grow faster or come back after treatment, but even these are manageable with the right care.

Why is it a Problem?

Even though meningiomas are usually benign, they can cause problems because:

• Your skull is like a closed box with limited space inside.
• As the tumour grows, it pushes on your brain, nerves, or blood vessels.
• This pressure can cause symptoms like:
  • Headaches (often worse in the morning)
  • Seizures (fits)
  • Weakness in an arm or leg
  • Vision problems
  • Personality or memory changes

Some meningiomas are tiny and cause no symptoms at all – these are often found by accident on a scan done for another reason (called an "incidental finding").

How Did I Get This?

In most people, we don't know why meningiomas develop. Some possible reasons include:

• Age: More common as you get older (peak age is 60-70 years)
• Sex: Twice as common in women than men (hormones may play a role)
• Radiation exposure: If you had radiation treatment to your head in the past (e.g., for childhood leukaemia), your risk is higher
• Rare genetic condition: A small number of people have a condition called neurofibromatosis type 2 (NF2), which causes multiple brain tumours including meningiomas

You did not cause this by anything you did. It is not contagious.

Do I Need Treatment?

It depends on several factors:

If Your Meningioma is Small and Causing No Symptoms:

• Your doctor may suggest "watch and wait" (also called observation or surveillance).
• You'll have regular scans (usually MRI) every 6-12 months to check if it's growing.
• Many small meningiomas stay the same size for years and never cause problems.
• You only need treatment if it starts to grow or causes symptoms.

If Your Meningioma is Causing Symptoms or Growing:

• Surgery is usually the best option if the tumour is in a location where it can be safely removed.
• The goal is to take out the whole tumour, including the part attached to the lining of the brain, to reduce the chance of it coming back.
• Most people recover well from surgery, especially if the tumour is on the surface of the brain.

If Surgery is Too Risky or the Tumour is in a Difficult Location:

• Stereotactic radiosurgery (also called Gamma Knife or CyberKnife) may be an option.
• This is NOT traditional surgery – no incision is made.
• Instead, highly focused beams of radiation are delivered in one session to stop the tumour from growing.
• It works very well for small tumours (less than 3cm) in hard-to-reach places like the skull base.

If the Tumour is Aggressive (High-Grade):

• After surgery, you may need radiotherapy (multiple sessions of radiation over several weeks) to reduce the risk of the tumour coming back.

Is Surgery Dangerous?

All brain surgery carries some risk, but for meningiomas:

• Good news: Because meningiomas grow on the surface (not inside the brain), they can often be removed safely without damaging your brain.
• Success rates: For tumours on the top or side of the brain (called "convexity"), over 80-90% of people do very well.
• Risks: The risks depend on where the tumour is located. Tumours at the base of the skull or near important nerves are more challenging, and there's a higher chance of temporary or permanent problems (e.g., double vision, numbness, weakness).

Your surgeon will discuss your specific situation and the risks and benefits with you before any operation.

What Happens After Treatment?

• If you had surgery: You'll need a scan 3 months later to make sure all the tumour was removed, and then yearly scans for several years to watch for any regrowth.
• If you had radiosurgery: The tumour usually shrinks slowly over 1-2 years. You'll need regular scans to monitor progress.
• Long-term outlook: For benign meningiomas that are completely removed, the chance of cure is very high (\u003e90%). Even if a small piece is left behind or it comes back, further treatment (more surgery or radiation) can usually control it.

Will I Be OK?

Yes, in the vast majority of cases. Meningiomas are one of the most treatable brain tumours:

• Most are benign and curable with surgery or radiosurgery.
• Even if they recur, they grow slowly and can be managed with further treatment.
• Modern neurosurgery and radiation techniques have excellent outcomes with low complication rates.

What You Can Do:

• Attend all follow-up appointments and scans.
• Report new symptoms (headaches, seizures, weakness) to your doctor immediately.
• If you're on "watch and wait," don't worry – this is a safe and appropriate strategy for small, asymptomatic tumours.

Support:

• Brain tumour charities (e.g., Brain Tumour Charity, American Brain Tumor Association) provide information and support groups.
• Ask your medical team for support with anxiety, practical issues, or second opinions.

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17. References

1. Buerki RA, et al. An overview of meningiomas. Future Oncol. 2018;14(21):2161-2177. PMID: 30084265

2. Ostrom QT, et al. CBTRUS Statistical Report: Primary Brain and Other Central Nervous System Tumors Diagnosed in the United States in 2016-2020. Neuro-oncology. 2023;25(12 Suppl 4):iv1-iv99. PMID: 37793125

3. Ostrom QT, et al. CBTRUS Statistical Report: Primary Brain and Other Central Nervous System Tumors Diagnosed in the United States in 2015-2019. Neuro-oncology. 2022;24(Suppl 5):v1-v95. PMID: 36196752

4. Sahm F, et al. cIMPACT-NOW update 8: Clarifications on molecular risk parameters and recommendations for WHO grading of meningiomas. Neuro-oncology. 2025;27(1):1-9. PMID: 39212325

5. Sahm F, et al. DNA methylation-based classification and grading system for meningioma: a multicentre, retrospective analysis. Lancet Oncol. 2017;18(5):682-694. PMID: 28314689

6. Louis DN, et al. The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. Acta Neuropathol. 2016;131(6):803-820. PMID: 27157931

7. Nassiri F, et al. A clinically applicable integrative molecular classification of meningiomas. Nature. 2021;597(7874):119-125. PMID: 34433969

8. Vlashi R, et al. The molecular biology of NF2/Merlin on tumorigenesis and development. FASEB J. 2024;38(13):e23783. PMID: 38967126

9. Nagai Yamaki V, et al. Dural-based lesions: is it a meningioma? Neuroradiology. 2021;63(6):1163-1179. PMID: 33459822

10. Guermazi A, et al. The dural tail sign--beyond meningioma. Clin Radiol. 2005;60(2):171-188. PMID: 15664571

11. Alali AA, et al. A proposed imaging scoring system to differentiate dural-based metastasis from meningioma using MR and CT images. BMC Med Imaging. 2025;25(1):16. PMID: 40375213

12. Simon M, et al. Grading meningioma resections: the Simpson classification and beyond. Acta Neurochir (Wien). 2024;166(1):44. PMID: 38261164

13. Wang JZ, et al. Molecular classification to refine surgical and radiotherapeutic decision-making in meningioma. Nat Med. 2024;30(10):2801-2815. PMID: 39169220

14. Pacult MA, et al. Surgical Management of High-Grade Meningiomas. Cancers (Basel). 2024;16(11):2117. PMID: 38893100

15. Flannery T, et al. Gamma Knife Radiosurgery for Meningioma. Prog Neurol Surg. 2019;34:283-293. PMID: 31096250

16. Jahanbakhshi A, et al. Gamma Knife stereotactic radiosurgery for cerebellopontine angle meningioma. Clin Neurol Neurosurg. 2019;186:105480. PMID: 31731053

17. Habibi MA, et al. Gamma knife stereotactic radiosurgery for neurofibromatosis 2 (NF2)-associated meningiomas; a systematic review and meta-analysis. Acta Neurochir (Wien). 2025;167(1):39. PMID: 39907804

18. Milano MT, et al. Single- and Multifraction Stereotactic Radiosurgery Dose/Volume Tolerances of the Brain. Int J Radiat Oncol Biol Phys. 2021;110(1):68-86. PMID: 32921513

19. Goldbrunner R, et al. EANO guideline on the diagnosis and management of meningiomas. Neuro-oncology. 2021;23(11):1821-1834. PMID: 34181733

20. Chen WC, et al. Radiation therapy of meningioma. Handb Clin Neurol. 2020;170:289-298. PMID: 32586500

21. Rogers CL, et al. High-risk Meningioma: Initial Outcomes From NRG Oncology/RTOG 0539. Int J Radiat Oncol Biol Phys. 2020;106(4):790-799. PMID: 31786276

22. Ganz JC, et al. Meningiomas. Prog Brain Res. 2022;268:269-290. PMID: 35074079

23. Tran AQ, et al. Spheno-Orbital Meningioma - Treatment Outcomes and Factors Influencing Recurrence. Ophthalmic Plast Reconstr Surg. 2023;39(5):491-496. PMID: 37133386

24. Raheja A, et al. Cavernous sinus meningioma. Handb Clin Neurol. 2020;170:349-361. PMID: 32586510

25. Westphal M, et al. Skull Base Meningiomas. Adv Exp Med Biol. 2023;1416:215-242. PMID: 37432619

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18. Revision Summary (High-Yield Points)

One-Sentence Summary

Meningiomas are the most common benign extra-axial brain tumours arising from arachnoid cap cells, typically presenting with seizures or focal deficits, diagnosed by MRI showing dural tail sign, and managed by observation, surgical resection (Simpson grading), or stereotactic radiosurgery depending on size, location, and symptoms.

Key Statistics to Memorize

• Incidence: 37-39% of all primary CNS tumours, 8.8 per 100,000 person-years
• F:M ratio: 2.3:1
• WHO Grade I: 80-90% (benign)
• 10-year survival: Grade I \u003e90%, Grade II 70-75%, Grade III 40-50%
• Recurrence (Grade I + Simpson I): ~10% at 10 years
• SRS control: 90-95% at 5 years

Must-Know Classifications

1. WHO Grading: Grade I (\u003c4 mitoses/10HPF), Grade II (≥4 mitoses OR brain invasion), Grade III (≥20 mitoses)
2. Simpson Grading: I (tumour+dura+bone), II (tumour+coagulate dura), IV (subtotal)
3. Molecular: NF2 loss (poor), TRAF7/AKT1 (good), CDKN2A/B deletion (Grade 3)

Classic Exam Traps

• Dural tail is NOT 100% specific (also metastases, lymphoma)
• Brain invasion = minimum WHO Grade II
• Foster-Kennedy syndrome (olfactory groove): ipsilateral optic atrophy + anosmia + contralateral papilloedema
• Adjuvant RT for WHO Grade III even after GTR

Management One-Liner

"Small asymptomatic → observe; symptomatic/growing → surgery (Simpson I/II); skull base \u003c3cm → SRS; Grade II + STR or Grade III → adjuvant RT."