Meningiomas are usually benign tumors which aris from the meninges covering of the brain and spinal cord, the arachnoid. About 1 of every 5 brain tumors are meningiomas. Since these tumors arise from the meninges, they almost always occur over the surface of the brain or under the brain in the skull base. These tumors generally do not invade the brain and therefore can often be totally removed by a craniotomy. However even with total excision, recurrence rates of 10% to 30% are reported, depending upon the length of follow-up. Skull base meningiomas often are more challenging to remove. Multiple meningiomas occur in 5% of patients, and meningiomas constitute 25% of intraspinal tumors. Rarely meningiomas may be malignant with rapid growth, invasion of the brain and frequent recurrence after surgery or radiation.

Meningiomas become symptomatic in several ways. During their slow growth they may irritate the brain causing epileptic seizures. Alternately, these tumors may compress adjacent brain producing progressive neurological symptoms, such as progressive weakness, or visual loss. Often these symptoms can be very subtle: progressive dementia or apathy may mimic depression in some patients with frontal meningiomas. Tumor which begin near less critical brain regions (so-called "silent brain") may become quite large producing symptoms of increased intracranial pressure such as headache and visual loss. On rare occasions these tumor may spontaneously bleed, producing an abrupt neurological deficit: a stroke.  Spinal meningiomas produce progressive weakness and numbness...interestingly these  spinal tumors are much most frequently seen in elderly females.

Fortunately meningiomas are relatively easy to diagnose as they have characteristic appearances on CT or MR images. Sometimes cerebral angiograms and MR spectroscopy can clinch the diagnosis in difficult cases.