Diagnosis
Most brain tumors are not detected until the patient starts having symptoms. If you have any symptoms of a brain tumor, your doctor will take your medical history and conduct a physical examination. Your doctor may then use the following tests to diagnose the cause of your symptoms:
Neurologic examination
Your doctor will perform a neurologic examination to test your brain and spinal cord function. A neurologic examination tests vital functions such as your vision, hearing, muscle strength, reflexes, coordination, and alertness. If your tests results are irregular, your doctor may refer you to a neurologist for further testing.
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Computed tomography (CT) scan
For a CT scan, you lie flat on a table while a machine rotates around your body and takes X-ray pictures. It produces detailed cross-sectional images of your brain, allowing doctors to pinpoint the exact location of the tumor in the brain. CT scans show bone, calcification, enlarged ventricles, bleeding and swelling very well but do not give the best picture of the soft tissue of the brain.
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Magnetic resonance imaging (MRI) scan
MRI scans use strong magnets to produce very detailed images of the brain and spinal cord. This test is very useful for examining the soft tissues in the head. MRIs can show differences in brain tissue, including abnormal growths and swelling (edema), allowing doctors to identify brain tumors.
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Positron emission tomography (PET) scan
For a PET scan, your doctor first injects a radioactive substance into your bloodstream. This substance is then absorbed by cells that use a lot of energy (metabolically active). Cells that are actively growing/dividing will take up a lot of the injected substance and therefore "light-up" on an X-ray. Areas of abnormal bright signal on the PET scan allow your doctor to pinpoint the location of a tumor. Because normal brain tissue is very metabolically active, a PET scan may not optimally allow for detection of a tumor in the brain.
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Lumbar Puncture (Spinal Tap)
Your doctor removes a sample of cerebrospinal fluid (CSF) from the bottom section of your spinal cord using a long, thin needle, after first numbing the area where the needle is to be inserted. Your doctor then sends the CSF to a laboratory to be examined under a microscope for any abnormalities or signs of tumor cells.
Surgical Biopsy (Craniotomy)
During a biopsy, the doctor removes a tissue sample from the tumor and has it examined under a microscope. A biopsy is the only way to be certain of the nature of the brain tumor, specifically, if the tumor is benign or malignant. For brain tumors, doctors usually take a biopsy sample at the same time you have surgery to remove the tumor. Your doctor may watch your tumor closely depending on its size, location, and how it was found before deciding to surgically remove it. When performing a craniotomy (surgery opening up the skull) to remove the tumor, your doctor will send a tissue sample to the laboratory to verify the diagnosis.
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Stereotactic Biopsy
Doctors perform stereotactic biopsies for tumors that are deep in the brain and difficult to reach. Your doctor drills a small hole in your skull and uses a CT scan or MRI to guide a needle to precise location of the tumor to remove a small tissue sample. If your tumor is in the brain stem or another critical area, your doctor may not be able to extract a tissue sample without harming healthy tissue.
