Glioma

Diagnosis

PET scan of glioblastoma multiforme

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Diagnosing a brain tumor usually begins with an exam by a neurologist, which includes checking vision, hearing, balance, coordination and reflexes. Depending on those results, the physician may request one or more of the tests described below. A biopsy is usually required to diagnose a brain tumor and confirm its type.

Magnetic Resonance Imaging (MRI) Scan
This scan uses magnetic fields to generate images of the brain. The patient lies inside a cylindrical machine for approximately an hour. MRI scans are particularly useful in diagnosing brain tumors, because they outline the normal brain structures in detail. Sometimes a special dye is injected into the bloodstream during the procedure to help better distinguish tumors from healthy tissue (MRI angiogram).

Computed Tomography (CT) Scan
A CT scan uses a sophisticated X-ray machine linked to a computer to produce detailed, two-dimensional images of the brain. A patient lies still on a movable table that is 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 to help better distinguish tumors (CT angiogram). A CT scan is painless and generally takes less than 10 minutes.

Angiogram
A special dye is injected into the arteries that go to the brain. The dye, which flows through the blood vessels in the brain, can be seen on X-ray. This test helps locate blood vessels in and around a brain tumor.

Other Brain Scans
Magnetic resonance spectroscopy (MRS), single-photon emission computed tomography (SPECT) or positron emission tomography (PET) scanning also help physicians gauge brain activity and blood flow. These scans can be combined with MRIs to help physicians understand a tumor's effects on brain activity and function. If a brain scan detects a tumor, especially multiple tumors, physicians may test for cancer elsewhere in the body.

X-rays of the Head and Skull
An X-ray of the head may show skull alterations indicating a tumor or calcium deposits sometimes associated with brain tumors. However, an X-ray is far less sensitive than brain scans and is used less often.

Biopsy

A biopsy is usually required to diagnose a brain tumor and confirm its type. In a biopsy, a tiny piece of tumor is removed for examination under a microscope. A biopsy can be perfomed separately or as part the surgery to remove the tumor.

The tissue is examined by a neuropathologist to determine the kind of tumor, which is critical to determining the proper treatment. It is important that this analysis be performed by a pathologist who specializes in brain tumors (a neuropathologist). Studies have shown that the diagnosis may change substantially for at least one-third of patients when an experienced neuropathologist does the review. Mayo's neuropathologists are internationally known for their expertise in diagnosing brain tumors.

Read more about brain tumor biopsies on the brain tumor pages.