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Diagnosing Astrocytoma

A diagnosis of astrocytoma will begin with a physical exam, during which a doctor will ask about symptoms and learn an individual’s history, including past illnesses and treatments, along with family history. The physician will check reflexes, balance, coordination, and muscle strength, and may order a blood test that includes a pituitary hormone test. The doctor may also ask a series of questions to check a person’s mental status.

Hearing and various vision tests may be performed.  A field-of-vision exam will determine the total area over which a person can see objects when looking straight ahead, as well as assess peripheral vision, or how much a person can still notice in other directions while looking straight ahead. Problems with vision may provide clues about the part of the brain affected by an astrocytoma.

If a doctor suspects a brain tumor, the next steps are usually imaging tests and other diagnostic tests to confirm the diagnosis and evaluate the tumor type, size, location, and speed of growth. These tests may include:

  • A magnetic resonance imaging (MRI) scan uses a strong magnetic field and radio waves to create detailed images that reveal the location of a tumor and which parts of the brain or spine are involved.
  • An MRI with contrast is aprocedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of the brain and spinal cord. A substance called gadolinium (the “contrast”) is injected into a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture.
  • Advanced MRIs include magnetic resonance spectroscopy (MRS) spectroscopy, which compares the chemical composition of normal brain tissue with abnormal tumor tissue, or perfusion MRI, which shows the amount of blood in an area of the brain (active areas take up the most blood, normal areas may take up lower amounts).
  • Functional magnetic resonance imaging (fMRI) and diffusion-tensor imaging (DTI) are techniques that may be used in surgical planning (called brain mapping) to help safely remove the astrocytoma without affecting healthy brain tissue. .

A CT scan is a diagnostic imaging technique in which a computer reads X-rays to create a three-dimensional map of soft tissue or bone. These scans are most useful for rapid diagnosis of a brain tumor when one is suspected.

A biopsy, in which a neurosurgeon removes a sample of tissue for testing, can provide a definitive diagnosis. For brain tumors, a needle is guided by a computer to remove the tumor sample. A pathologist will analyze the cells under a microscope to determine the tumor type, and a neurosurgeon may remove the tumor during the same surgery. A specialized test of the tumor cells from the biopsy, known as immunohistochemical staining, is used in the diagnosis of cancer cells to detect and view components of the tumor. 

Reviewed by: Rohan Ramakrishna, MD
Last reviewed/last updated: December 2020