Diagnosis

If your primary care doctor suspects you have a brain tumor, you may be referred to a specialist who is trained in treating brain and nervous system disorders (neurologist). Your doctor may recommend a number of tests and procedures, including:

• A neurological exam. During a neurological exam, your doctor may check your vision, hearing, balance, coordination, strength and reflexes. Problems in one or more of these areas may provide clues about the part of your brain that could be affected by a brain tumor.

• Imaging tests. Magnetic resonance imaging (MRI) is often used to help diagnose brain tumors. In some cases, a dye (contrast material) may be injected through a vein in your arm during your MRI study to help show differences in brain tissue.

  A number of specialized MRI scan components — including functional MRI, perfusion MRI and magnetic resonance spectroscopy — may help your doctor evaluate the tumor and plan treatment.

Other imaging tests may include computerized tomography (CT) scan and positron emission tomography (PET).

• Tests to find cancer in other parts of your body. To rule out other types of brain tumors that may have spread from other parts of the body, your doctor may recommend tests and procedures to determine where the cancer originated. Gliomas originate within the brain and are not the result of cancer that has spread (metastasized) from elsewhere.

• Collecting and testing a sample of abnormal tissue (biopsy). Depending on the location of the glioma, a biopsy may be performed with a needle before treatment or as part of an operation to remove the brain tumor.

  A stereotactic needle biopsy may be done for gliomas in hard-to-reach areas or very sensitive areas within your brain that might be damaged by a more extensive operation. During a stereotactic needle biopsy, your neurosurgeon drills a small hole into your skull. A thin needle is then inserted through the hole. Tissue is removed through the needle, which is frequently guided by CT or MRI scanning.

  The biopsy sample is then analyzed under a microscope to determine if it's cancerous or benign.

  A biopsy is the only way to definitively diagnose a brain tumor and give a prognosis to guide treatment decisions. Based on this information, a doctor who specializes in diagnosing cancer and other tissue abnormalities (pathologist) can determine the grade or stage of a brain tumor.

  The pathologist will also examine the physical appearance and growth rate of your biopsy sample (molecular diagnosis). Your doctor will explain the pathologist's findings to you. This information helps guide decision-making about your treatment plan.