How are brain tumors diagnosed?

Biopsies and diagnostic imaging, such as CAT scans and MRIs, are used to diagnose brain tumors and determine the type of tumor and treatment options.

If you have symptoms that suggest a brain tumor, your doctor will give you a physical exam and ask about your personal and family health history. You may have one or more of the following tests:

  • Neurologic exam: Your doctor checks your vision, hearing, alertness, muscle strength, coordination, and reflexes. Your doctor also examines your eyes to look for swelling caused by a tumor pressing on the nerve that connects the eye and the brain.
  • MRI: A large machine with a strong magnet linked to a computer is used to make detailed pictures of areas inside your head. Sometimes a special dye (contrast material) is injected into a blood vessel in your arm or hand to help show differences in the tissues of the brain. The pictures can show abnormal areas, such as a tumor.
  • CT scan: An x-ray machine linked to a computer takes a series of detailed pictures of your head. You may receive contrast material by injection into a blood vessel in your arm or hand. The contrast material makes abnormal areas easier to see.

Your doctor may ask for other tests:

  • Angiogram: Dye injected into the bloodstream makes blood vessels in the brain show up on an x-ray. If a tumor is present, the x-ray may show the tumor or blood vessels that are feeding into the tumor.
  • Spinal tap: Your doctor may remove a sample of cerebrospinal fluid (the fluid that fills the spaces in and around the brain and spinal cord). This procedure is performed with local anesthesia. The doctor uses a long, thin needle to remove fluid from the lower part of the spinal column. A spinal tap takes about 30 minutes. You must lie flat for several hours afterward to keep from getting a headache. A laboratory checks the fluid for cancer cells or other signs of problems.
  • Biopsy: The removal of tissue to look for tumor cells is called a biopsy. A pathologist looks at the cells under a microscope to check for abnormal cells. A biopsy can show cancer, tissue changes that may lead to cancer, and other conditions. A biopsy is the only sure way to diagnose a brain tumor, learn what grade it is, and plan treatment.

This answer is based on source information from the National Cancer Institute.

Dr. Tania B. Kaprealian, MD
Radiation Oncologist

Magnetic resonance imaging (MRI) with and without contrast is a common tool for diagnosing brain tumors. There’s also surgery, whether it be a biopsy, a subtotal resection (incomplete resection), a near-total resection or a gross-total resection (complete resection). These are all helpful for pathology, so doctors can look under the microscope and determine what exactly the tumor is.

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