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Small meningioma found by chance on a brain scan

A brain MRI or CT done for something else, such as headaches, dizziness or a head injury, may report a "small meningioma". This is a growth of the thin lining that covers the brain. Most are slow-growing and not cancer, and many never cause symptoms. (NHS)(EANO 2021)(Islim 2019) This page covers what the report means and the repeat scans guidance lists, not treatment.

What the report means

  • What it is. A meningioma grows from the thin layer of tissue covering the brain. It is the most common type of brain tumour that starts in the head, and it can sometimes be cancerous. (NHS)(NCI)
  • Mostly grade 1. Meningiomas are graded 1 to 3. In US data, 94.6% were grade 1, 4.2% grade 2 and 1.2% grade 3. (EANO 2021) Grade 1 tumours grow slowly. (NCI)
  • A scan suggests it. The diagnosis is usually made from the look of the MRI. Only removing tissue gives a definite grade, so a meningioma seen by chance is often called a "suspected" meningioma. (EANO 2021)
  • Benign versus cancer. Brain tumours can be benign, with no cancer cells, or malignant, with cancer cells that grow quickly. (MedlinePlus)

How common it is with age and in women

  • On brain scans. Meningiomas found by chance appear on 0.9% to 1.0% of brain MRIs in the general population. (EANO 2021) They make up about 15% of unexpected findings on brain MRI. (IMPACT protocol 2022)
  • Rises with age. In the US about 8.6 people per 100,000 are diagnosed each year, with a strong rise after age 65. (EANO 2021) A review of 19,559 people having a brain MRI found tumours of any kind in 0.70%, and the share rose with age. (Morris 2009)
  • More common in women. Grade 1 and 2 meningiomas are about 2.3 times more common in women than in men. (EANO 2021) In a review of meningiomas found by chance, 1,526 of the 1,919 people whose sex was recorded were women. (Islim 2019)
  • Smaller ones are found more often. As scans became more common, the share of meningiomas under 1 cm at diagnosis in the US rose from 6% in 2004 to 11% in 2012. (IMPACT protocol 2022) Radiation to the head, especially in childhood, raises the risk. (NCI)

How size, calcium and the scan pattern shape follow-up

  • Most stay quiet. In a 5-year study of 64 meningiomas found by chance, none caused symptoms. Three in four grew by 15% or more in volume, but more than 60% showed growth that levelled off. (EANO 2021) Across 20 studies of 2,130 people, 22.6% of tumours grew and 8.1% of people being watched developed symptoms, mostly within 5 years. (Islim 2019)
  • Size. A diameter of 3 cm or more was strongly linked to symptoms developing later. (Islim 2019) Larger volume also predicted growth. (EANO 2021)(Islim 2020)
  • Calcium (calcification). In a study of 232 untreated meningiomas, those without calcium were more likely to grow fast. Swelling around the tumour and a bright signal on one type of MRI image (T2) also predicted faster growth. (EANO 2021) Calcium seen on CT matches a dark signal on these MRI images. (Islim 2020)
  • Risk groups. The IMPACT model sorts meningiomas found by chance into low, medium and high risk using size, the MRI signal, swelling around the tumour and how close it sits to key nerves and blood vessels. Over 5 years, 3%, 28% and 75% of each group progressed, and the risk levelled off after 5 years. (Islim 2020)

Repeat scans guidance lists when there are no symptoms

  • Watching first. European guidance says observation is the first option for a meningioma found by chance that causes no symptoms, and that MRI is the best test for follow-up. (EANO 2021)
  • NICE (UK). For a meningioma found by chance with no symptoms: a scan at 12 months, and if there is no change, consider discharge or a scan at 5 years. (NICE NG99)
  • EANO (Europe). By consensus, a yearly MRI for 5 years, after which the gap between scans can be doubled, depending on age and general health. (EANO 2021)
  • New symptoms at any time. NICE advises a clinical review with a scan for anyone with a meningioma, including one found by chance, who develops new or changing nerve or brain symptoms. (NICE NG99)
  • Worry is real. NICE notes that routine scans and waiting for results can cause anxiety. (NICE NG99) See after an abnormal screening result.

How it ties to your age-based checks

No body recommends brain scans to look for meningiomas in people without symptoms. A review of unexpected brain MRI findings concluded they are not enough to justify screening healthy people. (Morris 2009) A finding like this is still a good moment to make sure your routine checks are up to date:

Other brain scan findings have their own pages: white matter changes on a brain MRI, small brain aneurysm found by chance and pituitary spot found by chance.

Who it applies to

Adults told that a brain MRI or CT done for another reason shows a small meningioma, with no symptoms from it. People with symptoms from the tumour, people with neurofibromatosis type 2 or past radiation to the head, and children are outside this page.

The NHS advises an urgent GP appointment or NHS 111 if you keep getting headaches, they do not go away or get worse, they wake you at night or are worse in the morning, or you have other brain tumour symptoms that do not go away. Call 999 (911 in the US) for a sudden, extremely painful headache or a first seizure. (NHS)

Routine age-based screening

A finding on a brain scan does not replace the routine screenings for your age. See screenings by age and gender.

Where they differ:

  • How many scans. NICE suggests a scan at 12 months and then discharge or one more scan at 5 years. (NICE NG99) EANO suggests yearly MRI for 5 years, then less often. (EANO 2021)
  • One schedule or a personal one. The IMPACT authors found little benefit from strict monitoring in low-risk people and in older people with several other health problems, and suggest some can be discharged with advice on which symptoms to watch for. (Islim 2020) The 2019 review found that follow-up varied widely between centres and that treating at diagnosis may lead to overtreatment. (Islim 2019)
  • How common. Figures range from about 3 per 1,000 to 1% of brain scans, depending on the population and the scan used. (IMPACT protocol 2022)(EANO 2021)

Your doctor decides what your result means for you.

Questions people ask

How common is a meningioma found by chance?

Meningiomas show up on about 0.9% to 1.0% of brain MRI scans in the general population, and they make up about 15% of unexpected findings on brain MRI. They become more common with age. (EANO 2021) (IMPACT protocol 2022)

Is a meningioma cancer?

Most are not. About 95% of meningiomas are grade 1, a slow-growing type that is not cancer. A small share are grade 2 or 3. (EANO 2021) (NCI)

Why are they more common in women?

Grade 1 and 2 meningiomas are about 2.3 times more common in women than in men. In a review of incidental meningiomas, 1,526 of 1,919 people were women. (EANO 2021) (Islim 2019)

Does a small one usually grow?

Many grow slowly or stop growing. In one 5-year study none of 64 incidental meningiomas caused symptoms, and more than 60% showed growth that levelled off. Across 20 studies, 8.1% of people being watched developed symptoms. (EANO 2021) (Islim 2019)

How often will I have a repeat scan?

NICE suggests a scan at 12 months and, if nothing has changed, either discharge or one more scan at 5 years. European guidance suggests a yearly MRI for 5 years, then less often. Your doctor decides. (NICE NG99) (EANO 2021)

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