Brain Stem Glioma - Childhood: Diagnosis

Approved by the Cancer.Net Editorial Board, 08/2020

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find out the cause of a medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, a brain stem glioma. They also do tests to learn if the tumor has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the tumor has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments could work best.

For most types of tumors, a biopsy is the only sure way for the doctor to know if an area of the body has a tumor. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory.

However, diffuse brain stem glioma is unlike most other tumors. Brain stem glioma is usually diagnosed with magnetic resonance imaging (MRI) only (see below).

In general, a biopsy is avoided in children with diffuse brain stem glioma because the results of the biopsy do not change treatment options and the procedure can have serious risks. Sometimes, a biopsy may be used in clinical trials or when a brain stem glioma has unusual features. By testing the part of the tumor removed during a biopsy, doctors may find certain molecular features that can help plan treatment. As new treatments based on this molecular information increase and the risk of a biopsy decreases, these procedures may be done more often.

For a focal brain stem glioma, a biopsy and removing the tumor with surgery may be considered. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.

This section describes options for diagnosing brain stem glioma. Not all tests listed below will be used for every person. Your child’s doctor may consider these factors when choosing a diagnostic test:

  • The type of tumor suspected

  • Your child’s signs and symptoms

  • Your child’s age and general health

  • The results of earlier medical tests

In addition to a physical examination, the following tests may be used to diagnose a brain stem glioma:

  • MRI. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill to swallow.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these pictures into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size. Sometimes, a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow. For a brain stem glioma, this test generally does not provide enough information to make a definite diagnosis, and an MRI is still needed.

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. As explained above, a biopsy is generally not done for the more common, diffuse type of brain stem tumor. However, for a focal tumor, it is often used to find out the type of tumor. If possible, a doctor called a neurosurgeon will remove a small piece of tissue from the brain. A neurosurgeon specializes in treating a CNS tumor using surgery. A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

After diagnostic tests are done, your child’s doctor will review all of the results with you. If the diagnosis is brain stem glioma, these results also help the doctor describe the tumor. This is called staging and grading.

The next section in this guide is Stages and GradesIt explains the system doctors use to describe the extent of brain stem glioma. Use the menu to choose a different section to read in this guide.