When a tumor emerges from the meninges (membranes that encapsulate the brain and the spinal cord), it's called a meningioma. While it's not precisely a brain tumor by definition, it is attributed to the same category due to the potential brain damage that it can cause, similar to that of actual brain tumors. Meningiomas grow over the course of many years and generally do not cause harm, but sometimes it can happen that the brain tissue or adjacent vessels and nerves get pressed and damaged by its mass.
Aside from radiation exposure, very specific injuries and type 2 neurofibromatosis, there are no known causes of meningioma. The increased frequency of meningiomas in women as opposed to their counterparts has been linked to the recent study that suggests progesterone (a hormone produced mostly by the ovaries) may cause and enhance meningioma growth. Malign meningiomas are known to cause seizures, headaches, blurred vision, arm and leg weakness, speech problems and numbness.
Studies show that maintaining a healthy body weight and avoiding unneeded dental x-rays helps reduce the risk of meningiomas. Benign meningiomas are generally observed without any medical intrusion, while malignant ones are treated with surgery, radiotherapy, and chemotherapy.