Meningiomas represent about 1 out of 3 primary brain and spinal cord tumors. They are the most commonly diagnosed primary brain tumors in adults. And although they evolve in the meninges, the layers of tissue that surround the outer part of the brain and spinal cord, they are referred to as brain tumors
The vast majority of meningiomas are benign, but these tumors can grow slowly and, if left undiscovered, can be severely disabling and life-threatening depending on their location. About 10 to 15 percent of meningiomas are malignant, or cancerous.
Michael McDermott, M.D. ., a neurosurgeon and the chief medical executive of Miami Neuroscience Institute , is a world-renowned leader  in neurosciences, with a clinical expertise in the field of meningioma surgery.
“I would say that the greatest proportion of meningiomas are discovered by chance,” explains Dr. McDermott. “Because of the wide availability of modern imaging, particularly with magnetic resonance imaging (MRI), studies are done for other reasons. That’s why these tumors are frequently discovered.”
Dr. McDermott is the editor of two books that were recently published: Handbook of Clinical Neurology: Meningiomas, Part 1, Vol. 169 (2020); and Part 2, Vol. 170 (2020).
Most meningiomas are usually discovered after an MRI or CT scan that someone may undergo after complaining of headaches or seizures, or possibly after a head injury. Since meningiomas are commonly slow-growing tumors, they often do not cause noticeable symptoms until they grow to certain size. In extreme cases, these tumors can alter a person’s behavior and mood.
In the following Q&A, Dr. McDermott provides more insight into meningiomas, including symptoms, risk factors and treatments.
What should people know about meningiomas?
“Meningiomas are the most common primary brain tumor in adults from over the age of 35 until death. Approximately 70 percent of these are low-grade and benign-behaving tumors. About 25 percent are a slightly higher grade, more aggressive and they need radiation therapy. They’re a very common tumor. They’re found frequently incidentally. For example, after a concussion, a CT scan is done for other reasons — and lo and behold — there’s a tumor and it’s a meningioma.
“Most of the meningiomas diagnosed do not require treatment. So, if the patient is asymptomatic, they don’t have symptoms specific to the tumor site and there’s no documented growth, then there’s no role for intervention. The patient can be safely observed.”
What are common symptoms associated with meningiomas?
“The most common symptoms for an adult patient with a brain tumor of any type are headaches, seizures, and progressive focal neurologic deficit. What does that mean? If the tumor overlies your motor cortex, you develop weakness on the other side. If it’s over your sensory cortex, you develop sensory symptoms. If it’s over your visual cortex, you develop visual symptoms. And then the other one is changing personality or behavior. That relates to the fact that the frontal lobe and temporal lobe are large parts of the brain and they control mood, insight, judgment, personality and behavior.
“So, if you have a big tumor pressing on your frontal lobe, you’ll have the so-called frontal lobe syndrome, which can encompass an apathetic and demotivational state, and depressed mood. Those are the kind of symptom complexes that the patients show. Every headache is not a brain tumor. But a headache that’s present for two weeks, is worse in the morning than the evening, and is associated with nausea and vomiting — that’s not normal.”
What are the top risk factors for meningiomas?
“Overwhelming, the majority, 90 percent or greater, are sporadic — meaning we don’t know why they occur. As I mentioned before, the majority are benign. But there are risk factors, such as prior radiation therapy exposure. With childhood leukemias, where the children are radiated prophylactically between the ages of three to seven. Now, there’s a national registry for those patients … understanding that there’s a 25-fold risk increase for the later development of meningioma.
“There are other associations with certain genetic syndromes, like neurofibromatosis (a genetic disorder that causes tumors to form on nerve tissue); non-causative links like breast cancer. Breast cancers are very common, and meningiomas are much less common. But they have similar genetic abnormalities. That doesn’t mean if you have breast cancer, you going to develop a meningioma, or vice versa.
“There’s an association with thyroid tumors; an association with fertility treatments; and an and an association with a family history — like two first-degree relatives with meningiomas — that might put you at a higher risk later in life for being diagnosed with one.”
What is the most common misconception that people may have about meningiomas?
“When you tell a patient that they have a benign tumor, they think that surgical treatment will be curative. But that’s not always the case and we have options for treatment. So, if we’re following a patient who’s asymptomatic, and they either become symptomatic or we have documented radiographic growth, then there’s a consideration for intervention or treatment.
“The different forms of treatment include surgery, radiation therapy or radiosurgery at diagnosis. And each of those forms of treatment has a different risk profile. Even 50 percent of benign tumors that are totally excised will recur 25 years after diagnosis. So, the key thing is that if you treat a patient with a benign tumor, they have to be followed essentially for their lifetime to rule out recurrence.”