Know thy harmless enemy

Sheryl Crow, diagnosed with a benign brain tumour, says she’s not worried. Here are some facts about the tumour — known as a meningioma — with which Crow was diagnosed. First, some definitions: The “oma” suffix refers to a swelling, tumour or cancer. It’s Greek. The “meninge” part of the word speaks to where these tumours originate: from the three membranes that cover the brain and the spinal cord, known as meninges. (Cancers are often described this way — melanoma is a cancer originating in the pigment-forming melanocyte cells in skin, lipomas are benign tumours originating from fat cells, etc.) The middle membrane, called the arachnoid, is the source of meningiomas. They can crop up in the spinal cord or in the brain in different places: on the outside of the brain (that’s a convexity meningioma), in a spot between the two sides of the brain (falcine and parasagittal meningioma) or somewhere in the ventricles — the fluid-filled spaces in the brain (intraventricular meningioma). And there are still more, sometimes with specific symptoms (an olfactory groove meningioma, for example, grows along the nerves between the nose and the brain and can lead to a loss of smell). Meningiomas are the most common type of tumour originating in brain tissue (as opposed to cancers that can originate at other sites but spread to the brain). They are usually benign, meaning they’re non-cancerous and slow-growing. “However, the word ’benign’ can be misleading in this case, as when benign tumours grow and constrict and affect the brain, they can cause disability and even be life-threatening,” a Brigham and Women’s Hospital website notes. Location is key, since even a slow-growing tumour can cause symptoms if it’s in a delicate spot in the brain, and starts pressing against it. In other cases, the tumour can grow for quite a while and get quite large before that happens. Often, people can walk around with meningiomas for years and not know, or discover it through an MRI exam undergone for some other problem. Symptoms of a meningioma depend on where it’s located, but commonly include headaches, seizures, numbness and blurred vision. Treatment of meningiomas depends a lot on each specific case. Doctor and patient might opt to watch the tumour if it’s not growing fast and not in a site that threatens life or causes symptoms, following them with periodic MRIs. In other cases, when the tumour is in a bad spot or is growing rapidly, surgery or radiation is preferred. The complexity of surgery depends on the location of the meningioma: Those on the outside of the brain are most easily removed, not surprisingly. But how common are they? Nowhere near as common as Crow’s publicist asserted when she said that “half of us” are walking around with one. But it’s true that a lot of us have them and don’t know it. After all, they would only be discovered if they caused symptoms that led to investigation, or if a brain scan for some other purpose revealed them by chance. They’re more common in older people and two to three times more common in women than men. They’re estimated to affect about 2 in 100,000 people. But the rates might be higher than that, and certainly higher in older people. To figure out the true rate, you’d have to go scan a large number of people with no symptoms. Exposure to radiation and having a genetic condition called neurofibromatosis type 2 both increase the risk for meningioma. Survivors of Hiroshima, for example, have higher rates, and some studies have suggested exposure to X-rays to the head during dental exams can up the incidence too. But that is probably more germane to older people because the X-ray doses used in dental exams were greater in the past. Scientists have also looked at whether exposure to female hormones could be linked to meningioma risk (inspired by the fact that women get them more often than men and the fact that these tumours do respond to the hormones). One study found a slightly increased risk for women who had taken oestrogen (without a progestin) for at least six months at or after menopause. From gulfnews