If you have symptoms, your doctor will perform a complete medical history and physical examination. A neurological assessment will evaluate, for example, your eye movement and pupil reaction; your hearing and senses of smell and touch; your reflexes and coordination; and your thinking ability and memory. Other tests that can help in diagnosing tumors may be ordered. Surgery is often required to determine if there is a brain tumor and to see what type of tumor it is.
When a brain tumor is suspected, a number of diagnostic tests are available to help validate the diagnosis:
X-rays: Your doctor may order a regular X-ray, which can show changes in the skull caused by a tumor or calcium deposits present in some tumors.
CT (computed tomography) scan: This special kind of X-ray uses a computer to create a series of images, or cross sections, of the brain. The patient must lie as still as possible as the table moves through a large, doughnut-shaped scanning device. Movement could blur the images produced by the scanner. A contrast agent may be injected into the bloodstream to help make a tumor more visible; abnormal tissue often absorbs more of the dye than does healthy tissue.
MRI ( magnetic resonance imaging): This imaging test provides clear pictures but takes longer to perform than a CT scan or an X-ray and is considerably more expensive. It uses a magnet, radio waves, and a computer to make a series of detailed three-dimensional pictures of the brain and spinal cord as the patient lies inside a large tube. In some cases, a contrast agent is used to make a tumor easier to see.
PET ( positron emission tomography) scan: This is a technique to obtain three-dimensional, color images of the brain that, unlike X-rays and CT scans, provide information about function rather than structures; the intensity of the color indicates chemical activity. By analyzing how tissue absorbs glucose tagged with a radioactive substance, doctors can often differentiate tumors from other types of tissue.
Angiography: This is an examination of blood vessels following the injection of a dye that makes the blood vessels visible on an X-ray. If a tumor is present, it may be visible on the X-ray.
Myelogram: This is a test in which a special dye is injected into the fluid of the spinal canal to help detect a tumor in the spinal cord on an X-ray.
EEG (electroencephalography): EEG is a test to study the electrical activity of the brain using electrodes placed on the scalp. Wires attached to the electrodes record the electrical impulses. Brain waves that have an abnormal frequency and amplitude may indicate the presence of a tumor.
MEG (Magnetoencephalography): MEG is a special device that maps the magnetic fields generated by the brain. It can be used to locate sources of seizures or other brain functions.
Spinal tap (lumbar puncture): A needle inserted into the lower back and into the spinal canal is used to remove a sample of cerebrospinal fluid. The fluid is then tested for the presence of cancer cells and certain molecules.
A biopsy, which removes a small sample of tissue to be analyzed for cancer cells, is the most accurate way to diagnose a brain tumor. A pathologist views the tissue under a microscope to determine how much it differs from normal tissue. This tells the doctor the grade of the tumor—how quickly the tumor is likely to grow and spread—so an effective plan of treatment can be devised.
A biopsy is performed in one of two ways. In a stereotactic brain biopsy, a surgeon makes a small hole in the skull and passes a needlelike biopsy instrument into the brain to retrieve tissue. The needle is guided by a CT or MRI scan to the location of the tumor by special computers. Alternatively, an open biopsy is when a tissue sample is taken by opening the skull, often during surgery to therapeutically remove tumor.
Last reviewed on 10/9/09
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