Pineal Tumors (cont.)
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Exams and Tests
The signs and symptoms of a brain tumor initially may be vague and come and go, making the diagnosis of a brain tumor difficult. Other diseases can cause similar signs and symptoms.
Diagnosing a brain tumor involves several steps. The doctor may perform a neurologic exam, which among other things includes checking the patient's:
Depending on the results of the neurologic exam, the doctor may request one or more of these tests:
Computerized Tomography (CT) Scan
The CT scan uses a sophisticated x-ray machine linked to a computer to produce detailed, two-dimensional images of the brain. The patient lies still on a movable table, guided into what looks like an enormous doughnut where the images are taken. A special dye may be injected into the bloodstream after a few CT scans are taken. The dye helps make tumors more visible on X-rays. The CT scan generally takes less than 10 minutes.
Magnetic Resonance Imaging (MRI) Scan
The MRI scan uses magnetic fields and radio waves to generate images of the brain. The patient lies inside a cylindrical machine for 15 minutes to an hour. MRI scans are particularly useful in diagnosing brain tumors because they outline soft tissues of the body as well as bone. Sometimes a special dye is injected into the bloodstream during the procedure. The dye usually makes tumors easier to distinguish from healthy tissue.
An angiogram involves injecting a special dye into the bloodstream. The dye, which flows through the blood vessels in the brain, can be seen by x-ray. This test helps show the location of blood vessels in and around a brain tumor.
X-rays of the Head and Skull
An x-ray of the head may show alterations in skull bones that could indicate a tumor. It may show calcium deposits, which are sometimes associated with brain tumors. However, a routine x-ray is a far less sensitive test than brain scans and so is used less often.
Other Brain Scans
Other tests, such as magnetic resonance spectroscopy (MRS), single-photon emission computerized tomography (SPECT) or positron emission tomography (PET) scanning, help doctors gauge brain activity by studying brain metabolism and chemistry as well as blood flow within the brain. These scans can be combined with MRIs to help doctors understand the effects of a tumor on brain activity and function, but doctors don't typically use them to make an initial diagnosis of brain tumor.
If the doctor sees what appears to be a brain tumor on a brain scan, especially if there are multiple tumors, he or she may test for cancer elsewhere in the patient's body before making a definitive diagnosis. Letting the doctor know of a prior history of cancer anywhere in the body, even many years earlier, is important.
The only test that can absolutely make a diagnosis of a brain tumor is a biopsy. This can be done as part of an operation to remove the tumor, or can be done in a separate procedure in which only a small sample of tissue is obtained. A needle biopsy may be used for brain tumors in hard-to-reach areas within the brain. The surgeon drills a small hole, called a burr hole, into the skull. A narrow, thin needle is then inserted through the hole. Tissue is removed using the needle, which is frequently guided by CT scanning.
The tissue is then viewed under a microscope to determine if it is a tumor, and if so, what type of tumor. Additional tests on the tissue are often done to help determine the exact type of tumor, which may help in guiding treatment.
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