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A neurological exam is usually the first test given when a patient complains of symptoms that suggest a brain tumor. The exam includes checking eye movements, hearing, sensation, muscle movement, sense of smell, and balance and coordination. The doctor will also test mental state and memory.
Advanced imaging techniques have dramatically improved the diagnosis of brain tumors.
Magnetic Resonance Imaging. Magnetic resonance imaging (MRI) is the gold standard for diagnosing a brain tumor. It does not use radiation and provides pictures from various angles that can enable doctors to construct a three-dimensional image of the tumor. It gives a clear picture of tumors near bones, smaller tumors, brainstem tumors, and low-grade tumors. MRI is also useful during surgery to show tumor bulk, for accurately mapping the brain and for detecting response to therapy.
A variant called magnetic resonance spectroscopy (MRS) is capable of providing information on the activity of the brain using magnetic resonance imaging. MRS can help provide information on the degree of malignancy and distinguish between dead tissue caused by radiation (radiation necrosis) and recurrent tumor cells.
Computed Tomography. Computed tomography (CT) uses a sophisticated x-ray machine and a computer to create a detailed picture of the body's tissues and structures. It is not as sensitive as an MRI in detecting small tumors, brain stem tumors, and low-grade tumors. It is useful in certain situations, however. Often, doctors will inject the patient with a contrast material to make it easier to see abnormal tissues. A CT scan helps locate the tumor and can sometimes help determine its type. It can also help detect swelling, bleeding, and associated conditions. In addition, computed tomography is used to check the effectiveness of treatments and watch for tumor recurrence.
Positron Emission Tomography. Positron emission tomography (PET) provides a picture of the brain's activity rather than its structure by tracking a sugar that has been labeled with a radioactive tracer. As with magnetic resonance spectroscopy (MRS), it is sometimes able to distinguish between recurrent tumor cells from dead cells or scar tissue caused by radiation therapy PET is not routinely used for diagnosis, but it may supplement MRIs to help determine tumor grade after a diagnosis. Data from PET may also help improve the accuracy of newer radiosurgery techniques.
Other Imaging Techniques. Numerous other advanced imaging techniques may be used for specific purposes, if available or under investigation.
A lumbar puncture is used to obtain a sample of spinal fluid, which is examined for the presence of tumor cells. Spinal fluid may also be examined for the presence of certain tumor markers (substances that indicate the presence of a tumor). However, most primary brain tumors do not currently have identified tumor markers.
A computed tomography (CT) scan or magnetic resonance imaging (MRI) should generally be performed before a lumbar procedure to be sure that the procedure will be safe.
A biopsy is a surgical procedure in which a small sample of tissue is taken from the suspected tumor and examined under a microscope for malignancy. The results of the biopsy also provide information on the cancer cell type. Biopsies may be performed as part of surgery to remove a tumor, or as a separate diagnostic procedure.
In some cases, such as brain stem gliomas, a standard biopsy might be too hazardous because removing any healthy tissue from this area can affect vital functions. In these cases, surgeons can use alternative techniques such as needle biopsy and stereotaxic biopsy. Stereotaxic biopsy is computer-directed type of needle biopsy that uses images provided from MRI or CT scans to provide precise information on the tumorÔ ' s location.
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