Meningiomas HADASSA EIN KAREM – NEUROSURGICAL ROTATION

Introduction:

Meningiomas are the most common benign brain tumours, and constitute about 15% of all intracranial tumours (gliomas – 45%)

Arises from the arachnoid layer of the meninges, principally the arachnoid villi and granulations.

“Meningioma” named by Harvey cushing in 1922 although described prior in late 1700’s

Peak incidence in middle age

Very uncommon in children

Women > men

Etiology:

No definite aetiological factor has been identified.

Possible risk factors include:

Trauma (unproven) noted occurenece in areas of meningies post trauma

Radiation (i.e. Nagasaki study, tinea capitis study)

NF2 (multiple – proven association with monosomy 22 even in non-NF2 patients in 50-80%)

Other chromosomal alterations

Sex hormones (increased incidence in females 2-4X) progesterone (50-100%) more commonly associated than estrogen (30%)

Position:Parasagital and falx 25%

Convexity 20%

Sphenoid wing 20%

Olfactory groove 12%

Suprasellar 12%

Posterior Fossa 9%

Ventricle 1.5 %

Optic sheath 0.5 %

Pathology:Meningiomas are classified by position rather than histology, as tumor behavior is a function of location and relationship to adjacent structures

5 major histological sub-types

• Syncytial or meningotheliomatous: sheets of cells with varying amounts of stroma

• Transitional: whorls of cells which may undergo hyalin degeneration with subsequent deposition of calcium salts. These calcified concentric psammoma bodies form the characteristic feature of many transitional meningiomas (may also be present in the syncytial or fibroblastic types).

• Fibroblastic: reticulin and collagen fibres.

• Angiomatous: predominance of vascular channels separated by sheets of cells. Histologically, these tumours resemble cerebellar hemangioblastomas.

• Malignant: cellular pleomorphism, necrosis, increased numbers of mitotic figures and local invasion of brain.

• Atypical: lack the histological features of malignancy, but have a biological behaviour intermediate between the typical and malignant meningioma. Most likely to recur.

Clinical presentation

Meningiomas present with features of: raised intracranial pressure focal neurological signs epilepsy

The position of the tumour will determine the features of the clinical presentation.

These tumours grow slowly and there is frequently a long history (years) of symptoms prior to diagnosis.

Parasagittal tumours Most often arise in the middle third of the skull

vault

May present with focal epilepsy and paresis, usually affecting the opposite leg and foot as the motor cortex on the medial aspect of the posterior frontal lobe is affected.

Tumours arising anteriorly are often bilateral and patients present with features of raised intracranial pressure. As these tumours involve the frontal lobes, pseudopsychiatric symptoms, as well as impairment of memory, intelligence and personality, may occur. Urinary incontinence is occasionally a symptom of a large frontal tumour, especially if it is bilateral.

Tumours arising from the posterior falx may affect the parieto-occipital region and produce a homonymous hemianopia. If the tumour lies above the calcarine fissure the inferior quadrant is more affected; when the tumour is below the fissure the upper quadrant is predominantly affected.

CT MRI

Convexity tumours

Convexity tumours may grow to a large size if situated in front of the coronal suture. They present with raised intracranial pressure.

More posterior tumours will cause focal neurological symptoms and focal epilepsy

CT MRI

Sphenoidal ridge tumoursInner sphenoidal ridge:

Cause compression of the adjacent optic nerve. patients may present with a history of uniocular visual failure. If the tumour is large enough to cause raised intracranial pressure papilloedema will develop in the contralateral eye.

The presenting features of primary optic atrophy in one eye and papilloedema in the other is known as the Foster Kennedy syndrome, and was described in 1911.

May also cause compression of the olfactory tract, resulting in anosmia.

Outer sphenoidal ridge:

Present with features of raised intracranial pressure, often severe papilloedema with relatively inconspicuous localizing symptoms or signs.

Tumours in this region occur as a thin sheet, and are known as ‘en plaque’.

They may cause an excessive bony reaction (hyperostosis) resulting in proptosis

Olfactory groove tumours Olfactory groove meningiomas cause

anosmia,initially unilateral and later bilateral.

May include symptoms of raised intracranial pressure, and failing vision either from chronic papilloedema or from direct compression of the optic nerve or chiasm causing visual field defects.

May also present with the Foster Kennedy syndrome and the intellectual and psychiatric problems caused by frontal lobe compression described for inner spheroidal ridge meningiomas.

MRIMRI

Suprasellar tumours

Arise from the tuberculum sellae will cause visual failure and a bitemporal hemianopia.

Lack of endocrine disturbance will distinguish the clinical presentation of this tumour from that of a pituitary tumour.

MRICT

Ventricular tumours

Tumours arising in the lateral ventricle present with symptoms of raised intracranial pressure extending over several years.

Associated with a mild global disturbance of function of one hemisphere.

Frequently a homonymous hemianopia.

CT

Posterior fossa tumours Posterior fossa tumours may arise from the

cerebellar convexity or from the cerebellopontine angle or clivus.

The cerebellopontine angle tumours simulate an acoustic neuroma with symptoms involving the acoustic nerve, trigeminal nerve and facial nerve, ataxia due to cerebellar involvement and raised intracranial pressure, often due to hydrocephalus caused by obstruction of the 4th ventricle.

Meningiomas arising from the clivus or the foramen magnum region may compress the brainstem directly.

CT MRI

MRI

Radiological investigationsCT scan:

Shows a tumour of slightly increased density prior to contrast; it enhances vividly and uniformly following intravenous contrast. Hyperostosis of the cranial vault may be a focal process at the site of the tumour attachment or, as seen with en plaque meningioma, a more diffuse sclerosis.

These bone changes may also be seen on plain skull X-ray.

MRI:

Meningiomas are usually isointense on T1- weighted images, but enhance intensely and usually homogeneously following administration of gadolinium.

Angiography:

No longer necessary as a diagnostic investigation but may be useful preoperatively to ascertain the position of the cerebral vessels.

It will demonstrate external carotid artery supply to the tumour with a characteristic tumour blush, differentiating it from a glioma or metastatic tumour

Angiography allows preoperative embolization of the tumour.

MRI pre-gad MRI post-gad

Cerebral Angiography

Preoperative management

Meningiomas are frequently surrounded by severe cerebral edema and patients should be treated with high-dose steroids (dexamethasone) prior to surgery if possible.

Preoperative embolization of the tumour vasculature may be considered advisable in some anterior basal and sphenoidal wing tumours where the major vascular supply is not readily accessible in the early stages of the operation.

Treatment Total surgical excision, including obliteration of the dural attachment.

Although usually possible, there are some situations where complete excision is not achievable because of the tumour position.

Tumours arising from the clivus, in front of the brainstem or those situated within the cavernous sinus, are notoriously difficult to excise without causing serious morbidity.

Radiation therapy may be used to treat residual tumours following subtotal resection,in order to reduce the risk of recurrent growth.

Stereotactic radiotherapy has been used to treat small meningiomas (less than 3 cm in diameter), particularly if the tumours are located in portions not easily amenable to surgery, or in the elderly or medically infirm patient.

Clinical studies have shown short-term control rates of over 90%, but long-term studies will be necessary to prove the efficacy and safety of focused radiation treatment

Postoperative management

Involves the routine management of patients following a craniotomy but with particular attention to the minimization of cerebral edema.

Steroid therapy is continued initially and gradually tapered.

Care is taken to avoid excessive hydration and the patient is nursed with the head of the bed elevated to promote venous return.

Neurological deterioration requires urgent assessment and a CT scan will determine the pathological cause, either postoperative haemorrhage or cerebral edema.

Tumour recurrence

Depends on the extent of tumour excision.

When the tumour and its dural origins are completely excised, the risk of recurrence is remote.

The most common source of recurrence is from a tumour that has invaded a venous sinus and which was not resected(e.g. superior sagittal sinus or cavernous sinus).

Recurrence is more common if the tumour has histological features of malignancy.