Diffuse Midline Glioma 

What is diffuse midline glioma?

Diffuse midline glioma, often shortened to DMG, is a rare and very aggressive type of brain tumour. It mainly affects children and young people, although adults can develop these tumours too. 

DMGs are a type of glioma, which means they develop from glial cells. These are the support cells in the brain and spinal cord that help nerve cells work properly. DMG is one of a group of aggressive childhood brain tumours known as paediatric-type diffuse high-grade gliomas, or PDHGGs.  

The word “midline” refers to where these tumours grow. DMGs form in the central areas of the brain or spinal cord, including the brainstem, thalamus and spinal cord. These areas control vital functions such as breathing, movement, balance and swallowing. 

All diffuse midline gliomas are classed as grade 4, meaning they grow very quickly. They are particularly difficult to treat because of where they grow and because they spread into the surrounding brain tissue. Sadly, outcomes remain very poor, with fewer than 1 in 10 children surviving two years after diagnosis.  

Diffuse intrinsic pontine glioma (DIPG) was the term previously used for diffuse midline gliomas that develop in the pons, part of the brainstem. Today, these tumours are classified as diffuse midline gliomas (DMGs), reflecting a broader understanding of this group of tumours and their shared biological features.

Brain Tumour Research has committed more than £2.7 million on research into paediatric high-grade gliomas since 2021. You can read more about what we are doing to find a cure for these devastating tumours here.

What are the symptoms of a brain tumour in children?

The symptoms a child experiences will often depend on where the tumour is growing in the brain or spinal cord. Symptoms can also vary depending on the child’s age and stage of development.

Symptoms may include:

  • Persistent headaches 

  • Nausea or vomiting

  • Seizures 

  • Vision or eye problems 

  • Difficulty with strength, balance, or coordination 

  • Noticeable changes in behaviour 

  • Issues with posture 

  • Delayed or halted puberty 

  • An unusually large head size in a baby 

Cancer in children is rare, and these symptoms are often caused by other conditions. However, it’s important to have your child checked by their GP.

How are diffuse midline gliomas diagnosed?   

Doctors use a combination of scans and tests to diagnose DMGs and to understand exactly which type of tumour a child has.

  • Brain scans

    MRI scans are usually the main test used to diagnose a DMG. These scans create detailed images of the brain and spinal cord, helping doctors see where the tumour is and how it is behaving. 

  • Biopsy (tissue sample) 

    In some cases, doctors may take a biopsy. This means removing a very small sample of tumour tissue so it can be examined in a laboratory.

    Because DMGs often grow in very sensitive areas of the brain or spinal cord, a biopsy is not always possible or safe. However, when it can be done, it can provide important information about the tumour and may help doctors understand whether a child could be eligible for certain clinical trials.

  • Molecular and genetic testing 

    If a tissue sample is available, doctors can carry out tests to look for changes in the tumour’s genes. These changes can help confirm the diagnosis and give more insight into how the tumour may behave.

    One of the key changes linked to diffuse midline glioma affects a gene called H3. This gene helps control how DNA is packaged inside cells and how certain instructions are switched on or off. In DMG, changes to this gene can disrupt normal cell behaviour and help drive tumour growth.

Frequently asked questions

What are the treatments for diffuse midline glioma? 

Diffuse midline gliomas are extremely difficult to treat. This is partly because they grow in areas of the brain and spinal cord that control essential functions. Surgery, which is often one of the first treatments considered for other brain tumours, is usually not possible for DMG because it could cause serious harm.

These tumours are also “diffuse”, which means tumour cells spread into the surrounding brain tissue. This makes them very hard to remove or target. They also tend not to respond well to standard chemotherapy.

Radiotherapy is currently the main treatment used for DMG. It can help slow the growth of the tumour and ease symptoms for a period of time, but it is not a cure.

Researchers are working to better understand these tumours and develop new, more effective treatments. This includes studying the genetic and molecular changes that help DMGs grow, and looking for ways to target them more precisely.

What causes diffuse midline gliomas?  

At the moment, the exact cause of diffuse midline gliomas is not known.

Research has shown that some DMGs are linked to changes in genes that help control how cells grow and behave. These changes are usually thought to happen by chance rather than being inherited. There is nothing a child or their family could have done to cause or prevent the tumour.

Are paediatric gliomas different to adult gliomas?  

Yes. In the past, childhood gliomas were often grouped together with adult gliomas or described using older terms, such as paediatric glioblastoma or diffuse intrinsic pontine glioma, known as DIPG.

Research has since shown that paediatric gliomas are biologically different from adult gliomas. This means they can have different genetic and molecular features and may behave differently. Because of this, the World Health Organization (WHO) now classifies paediatric gliomas separately from adult gliomas.

In the 2021 WHO classification of central nervous system tumours, paediatric gliomas are divided into two broad groups:

Paediatric-type diffuse low-grade gliomas, grades 1 to 2
These include tumour types such as pilocytic astrocytoma, ganglioglioma and other low-grade gliomas with specific genetic changes.

Paediatric-type diffuse high-grade gliomas, grades 3 to 4
This group includes diffuse midline glioma, H3 K27-altered; diffuse hemispheric glioma, H3 G34-mutant; diffuse paediatric-type high-grade glioma, H3-wild type and IDH-wild type; and infant-type hemispheric glioma.

Understanding these differences is important because it helps researchers develop treatments that are designed around the biology of childhood brain tumours, rather than relying on approaches developed for adult disease.

Find out more about PDHGG.

Are diffuse midline gliomas and diffuse intrinsic pontine gliomas the same thing?  

Diffuse intrinsic pontine glioma, or DIPG, is an older term that is still widely recognised, particularly by families and support organisations. It refers to a tumour that grows in the pons, part of the brainstem.

Diffuse midline glioma, or DMG, is the newer and broader term. It includes tumours that grow in the pons, but also those that develop in other midline areas such as the thalamus and spinal cord.

Some researchers are referring to DMGs that grow in the pons, and most likely would have previously been called DIPG, as pontine DMG.

Can adults develop DMGs? 

Yes. Diffuse midline gliomas mainly affect children and young people, but adults can develop them too, although this is rare.

This information is to provide general information and is NOT clinical information.