Brain Tumours

Meningioma

The most common primary brain tumour — usually benign, and often curable with surgery.

In brief

Arises from the meninges covering the brain, not from the brain itself
The most common primary brain tumour; usually benign (grade 1)
Often found incidentally and may only need monitoring
Diagnosed on MRI, with CT in selected cases
Managed by observation, surgery or radiosurgery depending on size and symptoms

What is a Meningioma?

A meningioma is a tumour that grows from the meninges — the thin protective membranes that cover the brain and spinal cord. It is not a tumour of the brain tissue itself; instead it arises on the surface, from the layer of cells lining these coverings, and grows inward, pressing on the brain or spinal cord rather than growing out of it. This distinction matters, because it means a meningioma can typically be separated from the brain and thus removed. Meningiomas are the most common primary brain tumour in adults — that is, the most common tumour that begins within the head rather than spreading there from elsewhere. They account for over 40% of all primary brain and central nervous system tumours, more than any other single type.1 The great majority are benign (non-cancerous) and slow-growing: about 80% are the lowest grade (WHO grade 1), and many never cause any symptoms at all.2 A substantial number — around 30% of those diagnosed — are found by chance on a scan performed for an unrelated reason, such as after a minor head injury or for headaches or dizziness.³ Because most meningiomas grow slowly and many never cause trouble, finding one is often far less alarming than it first sounds. A great many are simply monitored and never need treatment (see Should a Meningioma be Treated?, below).

Who Gets a Meningioma?

Meningiomas become more common with age and are usually diagnosed in later life, with the average age at diagnosis in the mid-to-late sixties.1,2 They are about twice as common in women as in men, and this female predominance is even more pronounced for meningiomas of the spine.²

Most meningiomas occur without any identifiable cause. Several factors are, however, recognised to increase the risk:

Previous radiation to the head — exposure to ionising radiation, particularly radiotherapy given to the head earlier in life, is the most firmly established environmental risk factor.²
Hormonal factors — meningiomas carry receptors for female sex hormones, which is thought to contribute to their being more common in women. Long-term use of certain high-dose progestogen hormone medications — in particular cyproterone acetate (an anti-androgen, or hormone-blocking, medication used for conditions such as severe acne, excessive hair growth and prostate cancer) — has been shown to increase the risk, and this risk rises with the cumulative dose and falls after the medication is stopped.4
A genetic predisposition — an inherited condition called NF2-related schwannomatosis (formerly neurofibromatosis type 2) predisposes to meningiomas, often multiple ones, though this accounts for only a small minority of cases.²

Where do Meningiomas Occur?

A meningioma can arise anywhere the meninges are found, over the surface of the brain, at the base of the skull, or along the spine. The most common sites are over the top and sides of the brain (the convexity), alongside the large midline vein at the top of the head (parasagittal and parafalcine), and along the sphenoid wing behind the eye.² The location, more than the size, tends to determine what symptoms a meningioma causes and how straightforward it is to treat.

How are Meningiomas Graded?

Meningiomas are graded from 1 to 3 under the World Health Organization (WHO) classification, according to how the tumour cells look under the microscope and, increasingly, their genetic features. The grade describes how the tumour is likely to behave — in particular how quickly it may grow and how likely it is to come back after treatment.⁵

Grade 1 (benign) — by far the most common, making up about 80% of meningiomas. These are slow-growing and, if they can be completely removed, are frequently cured.2
Grade 2 (atypical) — around 15–20% of meningiomas, a figure that has risen as the criteria for this grade have broadened. They grow more readily and are more likely to recur, so are watched more closely and more often need additional treatment after surgery.2
Grade 3 (anaplastic/malignant) — uncommon, around 1–2% of meningiomas. These are genuinely cancerous, grow quickly and tend to recur, and usually require combined treatment.2

The 2021 WHO classification refined this system by adding genetic (molecular) criteria to the traditional appearance under the microscope. Certain molecular changes — for example a TERT promoter mutation or loss of a gene called CDKN2A/B — now define a grade 3 meningioma in their own right, regardless of how the tumour looks down the microscope, because they identify tumours that behave aggressively.⁵ The great majority of meningiomas remain grade ¹.

Occasionally, a meningioma returns at a higher grade than it was originally. For grade 1 tumours this is uncommon — of the order of 1–4% over many years of follow-up.^6,7It is more frequent for grade 2 (atypical) tumours, of which roughly a quarter to a third eventually progress to a higher grade, and usually sooner.⁷ This is one of the reasons regular scans continue after treatment.

What are the Symptoms?

Most meningiomas cause no symptoms and are found incidentally. When symptoms do occur, they typically come on gradually — unless due to a seizure — often over months or years, reflecting the slow growth of the tumour, and depend far more on where the meningioma sits than on how large it is. They arise because the tumour presses on the adjacent brain, a nerve, or the spinal cord. Common features include:

Headaches — often mild and non-specific
Seizures (fits) — a meningioma is one of the more common tumours to cause a first seizure in an adult
Focal neurological symptoms — such as weakness or numbness of a limb, difficulty with speech, or unsteadiness, depending on the region involved
Visual symptoms — blurring, loss of part of the field of vision, or double vision, particularly with tumours near the eye or the base of the skull
Loss of smell — with tumours at the front of the skull base (the olfactory groove)
Personality or memory change — with larger tumours at the front of the brain, sometimes mistaken for other conditions
Symptoms in the spine — a spinal meningioma may cause weakness, numbness or difficulty walking, or disturbance of bladder or bowel function

A note on driving: a brain tumour that has caused a seizure, or that affects vision or concentration, usually means you must stop driving for a period and notify the licensing authority; your treating team will advise you in line with national fitness-to-drive guidelines.

How are Meningiomas Diagnosed?

Magnetic Resonance Imaging (MRI)

MRI with contrast (a gadolinium dye) is the key test. A meningioma has a very characteristic appearance: a well-defined mass attached to the coverings of the brain (dural-based) that takes up contrast strongly and evenly, often with a small “tail” of enhancement extending along the adjacent dura (the “dural tail”). The MRI shows the tumour’s size, precise location and its relationship to important structures such as blood vessels and nerves, and in the great majority of cases the diagnosis can be made confidently from the scan alone.⁸

Computed Tomography (CT)

CT is less detailed than MRI for the brain but complements it well for meningiomas. It shows calcification within the tumour (a sign of slow, long-standing growth) and any thickening of the overlying bone (hyperostosis), and is useful where MRI cannot be performed.

Other Tests

Occasionally a specialised nuclear medicine scan (a DOTATATE PET scan), which highlights receptors found on meningioma cells, is used in difficult cases — for example to distinguish tumour from scar tissue after treatment, or to define the extent of a tumour at the skull base.⁸ A biopsy is not usually needed before treatment, because the diagnosis is generally clear from imaging; the tissue diagnosis and grade are confirmed on the tumour removed at surgery.

Should a Meningioma be Treated?

Many meningiomas do not require treatment. Because so many are slow-growing, benign and cause no symptoms, a large proportion are best managed by careful observation rather than intervention — and the guiding principle is that the risk of any treatment must be less than the risk of the tumour itself.⁸

How likely is a meningioma to grow? For most people with a small, incidentally discovered meningioma the answer is reassuring. In studies following such tumours, only around 8% went on to develop symptoms, and fewer than one in four ever required any treatment.³ Whether a particular tumour is likely to progress can be estimated from its appearance on the scan — its size, its signal characteristics, and how close it lies to critical structures. Using these features, tumours can be sorted into low-, medium- and high-risk groups, with five-year risks of growth or progression of approximately 3%, 28% and 75% respectively; importantly, when a meningioma is going to progress it usually does so within the first few years, after which the risk settles.⁹

Observation (“watch and wait”) is the appropriate approach for many patients, particularly:

Small, incidentally discovered meningiomas that are causing no symptoms — the situation in which a meningioma is most often found. Studies following such tumours show that only a small minority ever go on to cause symptoms, and that when a tumour is going to grow it usually declares itself within the first few years.^3,9
Older patients, or those in whom the risks of surgery are increased, where a small or stable tumour is better left alone.⁸

Observation involves a repeat MRI after an interval to check for growth (typically 6 to 12 months to begin with), and then scans at lengthening intervals if the tumour remains stable, together with prompt review if any new symptoms develop.8 Features such as a small size, heavy calcification and a low signal on certain MRI sequences (such as the T2 and FLAIR sequences) all suggest a tumour that is unlikely to grow.⁹

Treatment — surgery or radiation — is generally considered when a meningioma is causing symptoms, is clearly growing on successive scans, or its size or position makes future problems likely. The decision is always made individually, weighing the tumour’s size, location and growth against the patient’s age, general health and wishes.⁸

How are Meningiomas Treated?

Surgery

Surgical removal is the main treatment for a meningioma, and for a grade 1 tumour that can be completely removed it is often curative.⁸ The operation involves a general anaesthetic and an opening in the skull (craniotomy) over the tumour, which is then separated from the surrounding brain and removed under the operating microscope. Where it can be done safely, the surgeon also removes the small area of dura from which the tumour grew, as this reduces the chance of it returning. The single most important factor determining whether a meningioma comes back is how completely it is removed — the more complete the removal, the lower the risk of recurrence.⁸ That said, complete removal is not always the right goal: when a tumour is wrapped around critical structures such as major blood vessels or nerves at the base of the skull, deliberately leaving a small amount behind and, if needed, treating it later with radiation is often far safer than attempting to remove every last part. This measured approach — removing what can be removed safely and no more — protects neurological function, which matters more than the satisfaction of a “complete” removal on a scan. The risks of surgery depend heavily on the tumour’s size and, above all, its location. For an accessible meningioma over the surface of the brain the risks are generally low; for a tumour at the base of the skull, near critical nerves and vessels, they are higher. The specific risks in any individual case are discussed in detail before surgery.

Radiotherapy and Radiosurgery

Radiation is a valuable treatment for meningiomas, used either as an alternative to surgery or in addition to it. It does not remove the tumour but is highly effective at stopping it growing.

Stereotactic radiosurgery (SRS) — despite its name, this is not an operation but a way of delivering a single, highly focused dose of radiation (for example with a Gamma Knife) precisely to the tumour, sparing the surrounding brain. It is well suited to small and moderate-sized meningiomas, particularly at the skull base, and to any tumour remaining or recurring after surgery. Because it is so precise, it can be used even for tumours lying close to the optic nerves — sometimes delivered in a few sessions, rather than one, to protect vision.10 For benign meningiomas, large radiosurgery series report the tumour is controlled in around 95% of cases at five years.¹¹
Fractionated radiotherapy — radiation given as a series of small daily treatments over several weeks, used for larger tumours and higher-grade tumours.

The role of radiotherapy after surgery depends on the grade. For grade 2 (atypical) meningiomas there is at present no definitive evidence establishing whether radiotherapy after surgery is beneficial, so the decision is made individually — jointly by your neurosurgeon and a radiation oncologist — taking account of how completely the tumour was removed and its other features.¹²For grade 3 (anaplastic) meningiomas, radiotherapy after surgery is standard and is recommended in all cases.¹³

Medications

There is no established drug treatment for meningiomas; unlike some other tumours, they do not respond reliably to any chemotherapy or targeted drug. Medicines have a supporting role only — for example a short course of corticosteroids (such as dexamethasone) to reduce swelling around a large tumour, or anti-seizure medication if seizures have occurred. For the rare high-grade meningioma that keeps returning despite surgery and radiation, drug therapies are the subject of ongoing research but remain investigational.⁸

Hormones and meningiomas

Most meningiomas carry receptors for progesterone, and some for oestrogen — part of why they are more common in women. This matters practically: progestogen-based medications (such as cyproterone acetate) and menopausal hormone (replacement) therapy can encourage a meningioma to grow, and stopping the responsible hormone often causes the tumour to stabilise or shrink, sometimes avoiding surgery.^14,15 If you have a meningioma, we will therefore review any hormone treatment you are taking; menopausal hormone therapy is generally best avoided where a safe alternative exists, and any decision to stop or continue it is made with you and your general practitioner, with a follow-up scan after any change.¹⁵Drugs that block these receptors directly have been tried without success and are not used.¹⁴

What is the Outlook?

For the great majority of people with a meningioma, the outlook is very good.

Grade 1 meningiomas — the large majority — are benign, and when completely removed are frequently cured; even when treated by observation or radiation, most are controlled long-term. They can recur years later, which is why follow-up scanning continues for some time, but the overall prognosis is excellent.⁸
Grade 2 (atypical) meningiomas are more likely to recur and need closer surveillance and, in selected cases, radiotherapy after surgery; many are nonetheless controlled for many years.¹²
Grade 3 (anaplastic) meningiomas are uncommon but serious, behaving more like a cancer, with a real risk of recurrence and a guarded outlook despite combined treatment.¹³

Because a meningioma’s behaviour depends so much on its grade, location and how completely it can be treated, your neurosurgeon will discuss what your particular tumour means for you at your consultation. For most people, the message is a reassuring one.

References

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Meningioma — patient information sheet PDF · prepared by Mr Jeremy Russell

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Content on this page is for education and information only and is not a substitute for advice from your doctor. Medically reviewed by Mr Jeremy Russell.