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Diffuse Intrinsic Pontine Glioma (DIPG)

Diffuse intrinsic pontine gliomas (DIPG) are highly aggressive and difficult to treat brain tumours found at the base of the brain. They are glial tumours, meaning they arise from the brain’s glial tissue (tissue made up of cells that help support and protect the brain’s neurons). These tumours are found in an area of the brainstem (the lowest, stem-like part of the brain) called the pons, which controls many of the body’s most vital functions such as breathing, blood pressure, and heart rate.

Diffuse intrinsic pontine gliomas account for 10 percent of all childhood central nervous system tumours. While DIPGs are usually diagnosed when children are between the ages of 5 and 9, they can occur at any age in childhood. These tumours occur in boys and girls equally and do not generally appear in adults.

Stages of DIPG

There are four stages or “grades” of gliomas, according to how the cells look under a microscope. Ordered from least severe to most severe, they are:


Low grade

  • Grade I (pilocytic)
  • Grade II (fibrillary)

High grade

  • Grade III (anaplastic)
  • Grade IV (glioblastoma multiforme)

When DIPGs are biopsied, they are usually grade III or grade IV. Occasionally, they are grade II, but because of their location in the brain they are still considered malignant. That being said, diffuse intrinsic pontine gliomas usually progress like grade IV glioblastoma multiforme tumours. They are very aggressive tumours and grow by invading normal brain tumours.

Causes and symptoms

For a long time, little was understood about DIPGs because clinicians feared that DIPGs could not be safely biopsied. However, recent and ongoing research has led to important discoveries, and more is being learnt about certain genetic mutations that might be causing DIPG.

Symptoms of DIPG usually develop very rapidly prior to diagnosis, reflecting the fast growth of these tumours. Most patients start experiencing symptoms less than three months – and often less than three weeks – before diagnosis. The most common symptoms include:

  • Rapidly developing problems controlling eye movements, facial expressions, speech, chewing, and swallowing (due to problems in the cranial nerves)
  • Weakness in the arms and legs
  • Problems with walking and coordination

Diagnosis of DIPG

Diffuse intrinsic pontine glioma is most commonly diagnosed from imaging studies. A doctor will typically perform a complete medical and physical examination. In addition, the treating doctor may order some of the following imaging tests:

  • Computerized tomography scan (also called a CT or CAT scan) – a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. CT scans are more detailed than general x-rays.
  • Magnetic resonance imaging (MRI) – a diagnostic procedure that uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs and structures within the body. MRI provides greater anatomical detail than CT scan and does a better job of distinguishing between tumours, tumour-related swelling and normal tissue.
  • Magnetic resonance spectroscopy (MRS) – a diagnostic test conducted along with an MRI. It can detect the presence of organic compounds around the tumour tissue that can identify the tissue as normal or tumour, and may also be able to tell if the tumour is a glial tumour or if it is of neuronal origin (originating in a neuron, instead of an astrocytic or glial cell).
  • Biopsy – with recent advances in neuro-surgical techniques, it is now possible to safely biopsy diffuse intrinsic pontine glioma (when performed by a pediatric neuro-surgeon with specific expertise in performing biopsies for DIPG).

Prognosis

Unfortunately, the prognosis for DIPGs remains very poor. Although a small percentage of patients survive this disease and new DIPG research may provide the key to improved treatment options, currently only 10% of children with DIPG survive for 2 years following diagnosis, and less than 1% survive for 5 years. The median survival time is 9 months from diagnosis

Information has been sourced from defeatdipg.org and danafarberbostonchildrens.org