Meningiomas arise from the coverings over the brain or spinal cord. They usually grow slowly, and most are benign. Many meningiomas form a discrete mass, compressing adjacent neural tissue. Other meningiomas, particularly those located along the cranial base, grow as a sheet and surround, as well as compress, cranial nerves and arteries.

Meningiomas can arise in any location within the cranial cavity although there are certain areas in which they are more common, and where they cause characteristic symptoms. Meningiomas may arise from the dura over the surface of the brain (convexity meningiomas), from the wall of the sagittal sinus and adjacent dura and falx (parasagittal meningiomas), or from the falx (falx meningiomas). Their symptoms and signs depend on the location of the tumour and they usually progress gradually. Patients may present with a seizure; headache is uncommon. Frontal tumours may cause a change in personality or mental function; frontal–parietal tumours may cause progressive weakness or cortical sensory loss in the opposite extremities or dysphasia when the dominant cerebral hemisphere is involved; occipital tumours cause visual symptoms. Meningiomas arising from the midline of the floor of the frontal fossa (olfactory groove meningioma) can cause dementia, personality change, headache, or visual symptoms. Loss of smell is rarely noted by the patient, but this may be found on special examination. Tumours originating from the area of the tuberculum sellae and anterior clinoid cause gradual visual loss. When they grow from the sheath of the optic nerve in the orbit and optic canal they may cause gradual visual loss and proptosis of the eye. Meningiomas arising along the bone of the sphenoid wing may extend into the orbit and into the temporal fossa intracranially. Proptosis of the eye is often the only symptom. Meningiomas in the region of the cavernous sinus may involve the internal carotid artery. Ptosis of the eyelid due to involvement of the third cranial nerve or double vision due to impaired ocular motion are the most common symptoms. Tumours may occur in the trigone of the lateral ventricle of the cerebral hemisphere. Headache may be due to obstruction of spinal fluid flow, and pressure on the adjacent brain may cause a visual field defect.

Hearing loss, facial numbness, and ataxia are common symptoms caused by meningiomas affecting the petrous bone or the clivus and extending into the cerebellopontine angle. Meningiomas arising from the tentorium compress the occipital lobe, cerebellum, or cranial nerves at the tentorial edge. Meningiomas in the region of the foramen magnum may cause cervical pain, neck stiffness, dysaesthesia, and clumsiness of the hands and fingers.

The diagnosis is usually made from the characteristic findings on MRI or CT scan. The location, the sharp demarcation of the surface of the tumour, and dense enhancement following intravenous contrast injection suggest the diagnosis. Oedema may be present in the adjacent brain areas. Some meningiomas, particularly those involving the sphenoid wing, may be associated with hyperostosis, best seen on the CT scan. Angiography is sometimes indicated to define the relationship between the tumour, the arterial circulation, and venous sinuses. There is often a characteristic development of new or enlarged arteries supplying the tumour, and a stain of dye in the venous phase of the study.

Surgery is the appropriate treatment for most patients. Careful preoperative preparation, the use of microneurosurgical techniques, excellent anaesthesia, and specialized postoperative care all produce a very low operative mortality rate and little serious morbidity. In some patients with highly vascular tumours pre-operative embolization is indicated.

Radiation therapy may be used when the risks of removing the tumour are high and the meningioma is enlarging or causing major neurological disability. Observation with periodic MRI scans and clinical evaluation may be indicated in patients with asymptomatic meningiomas and in some patients with tumours causing mild symptoms, particularly those of the cranial base and those occurring in the elderly.

Complete removal of meningiomas, including any involved dura and bone, gives a high probability of cure. However, the goal of surgery is to preserve and improve function. In some patients total removal of the tumour carries the risk of significant morbidity, and it is better judgement to leave some tumour and to monitor the patient's progress or to use radiation therapy.

Tumours of the convexity, parasagittal, falx, olfactory groove, and intraventricular regions, and some suprasellar, petrous, and tentorial meningiomas can be removed completely. Meningiomas of the cranial base involving the cavernous sinus region, sphenoid wing, and clivus, and large tumours in the suprasellar and petrous regions are more difficult to remove completely. Extensive but subtotal removal of the tumour may be followed by resolution of symptoms and many years without significant recurrence.

Guthrie BL, Ebersold MJ, Scheithauer BW. Neoplasms of the intracranial meninges. In Youmans JR, ed. Neurological Surgery, 3rd edn. Philadelphia: Saunders, 1990: 3250–315.

Ojemann RG. Meningiomas: clinical features and surgical management. In Wilkins RH, Tengachary SS, eds. Neurosurgery. Vol 1. New York: McGraw-Hill 1985: 635–54.