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Diffuse Midline Gliomas Diagnosis and Treatment

MRI of a diffuse midline glioma in the brain.

Credit: NCI-CONNECT Staff

Diffuse midline gliomas are primary central nervous system (CNS) tumors. This means they begin in the brain or spinal cord. Diffuse midline glioma is a rare subtype of glial tumors. 

To get an accurate diagnosis, a piece of tumor tissue will be removed during surgery, if possible. A neuropathologist should then review the tumor tissue.

What are the grades of diffuse midline gliomas?

Primary CNS tumors are graded based on the tumor location, tumor type, extent of tumor spread, genetic findings, the patient’s age, and tumor remaining after surgery, if surgery is possible.

Diffuse midline gliomas are all grade 4 tumors (also written as grade IV). This means they are malignant (cancerous) and fast-growing.

What do diffuse midline gliomas look like on an MRI?

Diffuse midline gliomas usually appear as a mass that has spread in the middle area of the brain. The tumor shows degrees of brightness with contrast. In adults, the diagnosis of diffuse middling glioma can’t be made by imaging alone because the tumors look similar to glioblastomas and other high-grade brain cancers.

What causes diffuse midline gliomas?

Cancer is a genetic disease – that is, cancer is caused by certain changes to genes that control the way our cells function. Genes may be mutated (changed) in many types of cancer, which can increase the growth and spread of cancer cells. The cause of diffuse midline gliomas is not known. People with gene changes that can be passed down through families, such as Li-Fraumeni syndrome and neurofibromatosis type I, are at increased risk for developing a diffuse midline glioma. Changes in a gene known as the h3K27M mutation, have also been linked to the growth of diffuse midline glioma.

Where do diffuse midline gliomas form?

Diffuse midline glioma most often forms in the pons in the brainstem, thalamus, spinal cord, and cerebellum.  It’s uncommon for these tumors to occur in other areas of the CNS. The tumors are named, in part, based on the locations where these tumors most often occur.  Therefore, tumors in other brain or spine locations thought to be diffuse midline glioma should be reviewed by neuro-oncology providers with experience in treating people with these tumors.

Diffuse midline glioma is a rare type of astrocytoma that look similar under the microscope to other more common astrocytomas, such as a glioblastoma. Since it can be hard to tell them apart, they require molecular testing. Some diffuse midline gliomas have changes in histone-related genes, the most common is h3K27M.  Review by a neuropathologist is recommended to confirm this diagnosis.

Do diffuse midline gliomas spread?

Diffuse midline gliomas are fast-growing tumors and can spread to other areas of the CNS through cerebrospinal fluid (CSF). The tumor can invade nearby tissue and extend beyond what can be seen on MRI or by the surgeon during surgery. Diffuse midline glioma, however, usually grow and come back in the same location in which they first appeared.

What are the symptoms of diffuse midline gliomas?

Symptoms related to diffuse midline glioma depend on the tumor’s location. Here are some possible symptoms that can occur.

Diffuse Midline Glioma Symptoms
  • Double vision
  • Problems swallowing
  • Weakness on one or both sides of the body
  • Loss of balance 

Diffuse midline glioma in the brain also may cause increased pressure within the skull due to production of too much CSF or blockage of its normal flow. This problem is known as hydrocephalus.

Signs and symptoms of hydrocephalus may include:

  • Nausea
  • Vomiting
  • Irritability
  • Headaches
  • Blurred or double vision
  • A strong desire to sleep
  • Seizures

People with a diffuse midline glioma in the spine may have:

  • Progressive weakness
  • Numbness
  • Problems with bowel and bladder control

Who is diagnosed with diffuse midline gliomas?

Diffuse midline gliomas occur in both children and adults. Diffuse midline glioma tends to occur in children. Diffuse midline gliomas occur more often in males than females. They are most common in white and non-hispanic people. An estimated 6,033 people are living with this tumor in the United States.

Diffuse Midline Glioma Statistics

What is the prognosis of diffuse midline gliomas?

The likely outcome of the disease or chance of recovery is called prognosis.

Diffuse Midline Glioma Prognosis

The relative 5-year survival rate for diffuse midline glioma is 48.9% but know that many factors can affect prognosis. This includes the tumor grade and type, traits of the cancer, the person’s age and health when diagnosed, and how they respond to treatment. If you want to understand your prognosis, talk to your doctor.

What are the treatment options for diffuse midline gliomas?

The first treatment for diffuse midline glioma is surgery, if possible. The goal of surgery is to obtain tissue to determine the tumor type and to remove as much tumor as possible without causing more symptoms for the person.  The brainstem, thalamus, and spinal cord are sensitive locations in the CNS and surgery in these areas can cause serious loss of function. Diffuse midline glioma may sometimes be treated with radiation therapy alone without a biopsy if the risk of biopsy is thought to be too high.  A procedure such as a ventriculoperitoneal shunt, may also be needed to redirect the flow of cerebrospinal fluid if the patient has hydrocephalus.

Diffuse midline gliomas usually require further treatments. Treatments may include radiation, chemotherapy, or clinical trials. Surgery is followed by radiation therapy in most cases.  Chemotherapy is sometimes given with radiation therapy, or after radiation.  However, there is no standard chemotherapy regimen, and each plan should be tailored to each patient.  Review of diffuse midline glioma by a team of experts including neuro-oncologists, neuroradiologists, radiation oncologists, and neurosurgeons is important to determine the best treatment plan.  Clinical trials, with new chemotherapy, targeted therapy, or immunotherapy drugs, may also be available and can be a possible treatment option.

Open Clinical Studies for Diffuse Midline Gliomas

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