Meningioma

Meningioma is a primary extra axial tumour arising from arachnoid cap cells.

Most are slow growing and benign, but biological behaviour ranges from indolent incidental tumours to aggressive recurrent malignant disease.

Common locations include:

• Cerebral convexity
• Parasagittal region
• Sphenoid wing
• Olfactory groove
• Tuberculum sellae
• Petroclival region
• Posterior fossa
• Foramen magnum
• Spinal canal

Symptoms result from:

• Brain compression
• Cranial nerve compression
• Venous sinus involvement
• Peritumoral oedema
• Seizures

WHO grading

WHO grade 1

Most meningiomas.

Generally slower growing.

WHO grade 2

Includes atypical, clear cell and chordoid meningiomas and tumours meeting higher mitotic or brain invasion criteria.

Higher recurrence risk.

WHO grade 3

Aggressive malignant meningioma.

A TERT promoter mutation or homozygous CDKN2A/B deletion is sufficient for WHO grade 3 designation even when histological appearance is not frankly anaplastic.

Simpson resection grading

Useful for describing surgical completeness.

Grade I

Complete tumour removal plus involved dura and abnormal bone.

Grade II

Complete tumour removal with coagulation of dural attachment.

Grade III

Complete tumour removal without resection or coagulation of dural attachment or involved extradural tissue.

Grade IV

Subtotal tumour removal.

Grade V

Simple decompression or biopsy.

Modern management does not sacrifice critical venous sinuses or cranial nerves solely to achieve a lower Simpson grade when the neurological morbidity would outweigh recurrence benefit.

Many meningiomas are incidental.

Symptomatic disease depends on location.

Presentations include:

• Seizure
• Headache
• Progressive focal weakness
• Cognitive or personality change
• Visual loss
• Cranial nerve palsy
• Ataxia
• Raised ICP with large tumours

Parasagittal lesions can invade the superior sagittal sinus.

Tuberculum sellae lesions commonly present with progressive visual impairment.

Sphenoid wing tumours can involve:

• Optic nerve
• Cavernous sinus
• Internal carotid artery
• Orbit

MRI brain with gadolinium: principal imaging study.

Typical appearance is an extra axial enhancing mass with broad dural attachment.

CT is useful for:

• Hyperostosis
• Calcification
• Bone invasion
• Surgical planning at skull base

CT or MR venography is useful for parasagittal tumours involving major venous sinuses.

Definitive grade requires tissue diagnosis.

Observation

Observe an asymptomatic incidental tumour when:

• Small
• No significant mass effect
• No concerning growth pattern
• Patient age or comorbidity favours conservative care

Use interval MRI.

Growth rather than size alone should influence treatment.

Surgery

Operate when there is:

• Progressive neurological deficit
• Seizures attributable to the lesion
• Significant growth
• Mass effect
• Raised ICP
• Threatened vision
• Diagnostic uncertainty

Maximal safe resection is the primary treatment for symptomatic surgically accessible meningioma.

The objective is maximum safe resection, not neurological sacrifice for radicality.

Examples:

Convexity meningioma

Often allows complete resection including dural attachment.

Parasagittal meningioma

If a patent major superior sagittal sinus is densely invaded, subtotal tumour removal plus postoperative surveillance or radiotherapy can be preferable to catastrophic venous infarction.

Skull base meningioma

Aggressive dissection from:

• Cranial nerves
• Brainstem
• Internal carotid artery

may create more morbidity than leaving a small controlled residual.

Peritumoral oedema

For significant symptomatic vasogenic oedema:

Dexamethasone 4 mg IV or orally every 6 hours

is a common starting regimen in a significantly symptomatic adult.

Use the lowest effective dose and taper after surgical decompression or clinical improvement.

Steroids are not required for every meningioma.

Seizures

Treat a documented tumour related seizure with an antiseizure medication.

A practical option is:

Levetiracetam 500 to 1000 mg orally or IV every 12 hours

with dose adjustment according to renal function and seizure control.

Routine long term prophylaxis in a seizure free patient undergoing uncomplicated tumour surgery is not necessary in every case.

Radiotherapy

WHO grade 1

Use radiotherapy for:

• Unresectable symptomatic tumour
• Progressive residual or recurrent tumour
• Skull base tumour where surgery carries major morbidity

Stereotactic radiosurgery is particularly useful for small well defined tumours away from highly radiosensitive structures.

WHO grade 2

After subtotal resection, postoperative radiotherapy is commonly used because recurrence risk is high.

After complete resection, postoperative radiotherapy is individualised according to:

• Histological features
• Molecular risk
• Location
• Recurrence history

WHO grade 3

Requires postoperative fractionated radiotherapy after maximal safe resection because local recurrence risk is extremely high.

Systemic therapy remains investigational for most recurrent meningiomas.

Follow up

Surveillance intensity should increase with:

• Higher grade
• Residual tumour
• Aggressive molecular markers
• Previous recurrence

New growth after previous treatment requires assessment of whether:

• Repeat surgery
• Radiosurgery
• Fractionated radiotherapy

provides the best local control.