Diagnosis

Doctors use many tests to diagnose a brain stem glioma and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most tumors, a biopsy is the only way to make a definitive diagnosis. However, biopsies are rarely used and are often specifically avoided in children with diffuse brain stem glioma because the results of the biopsy do not influence treatment, and they can have major risks. In addition, the diagnosis can often be made by magnetic resonance imaging (MRI) alone (see below). Diffuse brain stem glioma is unlike most other tumors in this regard. For a focal tumor, a biopsy and surgical tumor removal may be considered. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your child’s doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
  
  
• The type of tumor suspected
  
  
• Severity of symptoms
  
  
• Previous test results

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 contrast medium (a special dye) may be injected into a patient’s vein to create a clearer picture.

Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium is injected into a vein to provide better detail. For a brain stem glioma, this test generally does not provide enough information to make a definite diagnosis, and an MRI is required.

Biopsy.A biopsy is the removal of a small amount of tissue for examination under a microscope. 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 determine the type of tumor. If possible, a neurosurgeon (a specialist who operates on the brain and spine) will remove a small piece of tissue from the brain. The sample removed during the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease).

Learn more about what to expect when having common tests, procedures, and scans.

Find out more about common terms used during a diagnosis of cancer.