Tumours of the cerebral hemispheres extrinsic

Extrinsic tumours arise outwith the brain substance. MENINGIOMA

Meningiomas constitute about one-fifth of all primary intracranial tumours. They are slow growing and arise from the arachnoid granulations. These lie in greatest concentration around the venous sinuses, but they also occur in relation to surface tributary veins. Meningiomas may therefore develop at any meningeal site. Occasionally they are multiple. Meningiomas present primarily

Sites of intracranial meningioma

Convexity ___ ____Parasagittal/falcine

in the 40-60 age group and have a slight female preponderance. They are principally benign tumours, although a malignant form exists. Pathology

Various histological types are described - syncytial, transitional, fibroblastic and angioblastic; different types may coexist within the same tumour. These distinctions serve little clinical value, although it is important to identify the haemangiopericytic variant of the angioblastic group as well as the malignant type, as these indicate the likelihood of rapid growth and a high rate of recurrence following removal.

Olfactory groove (10%)

Olfactory groove (10%)

The remainder arise from the middle fossa, orbital roof and lateral ventricle

Macroscopic appearance The dural origin usually incorporates the main arterial supply. The tumour surface, although often lobulated, is well demarcated ^^ from the surrounding brain and attached only by small bridging vessels.

Marked oedema often develops in the ------

surrounding brain.

A reactive hyperostosis develops in adjacent bone, forming a swelling on the inner table. Hyperostosis affecting the outer table may produce a palpable lump. Tumour tissue may infiltrate adjacent bone.

Parasagittal tumours may Ij^Yj^. invade and obstruct the si____sagittal sinus.

~ Tumour texture and vascularity varies considerably from patient to patient - some are firm and fibrous, others soft. Calcified deposits (psammoma bodies) are often found.

En-plaque meningioma: In some patients, rather than developing a spherical form, the meningioma spreads 'en-plaque' over the dural surface. This type often arises from the outer aspect of the sphenoid wing.

localised neurological disease and its management a intracranial

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