Brain Tumors

Diagnosing

If your doctor suspects a brain tumor, he or she will perform a thorough exam, which will include questions about your medical history and symptoms, along with a neurologic exam to assess elements such as vision, hearing, strength and reflexes. Based on the results, your doctor may add any of the following tests to diagnose and evaluate how advanced the tumor may be.

Imaging Tests

Angiogram uses X-rays to map out blood flow in the brain. You will be given a special dye (called a “contrast”) before the scan. The X-ray images map how the dye moves through the artery and into the blood vessels of the brain. Movement of the dye helps identify the network of blood vessels that supply the tumor.

Computed tomography (CT) produces three-dimensional, cross-sectional X-ray images, so it can provide more precise details than a standard X-ray. For this test, a special dye (called a “contrast”) may be injected into your vein, and you likely will be asked to swallow another type of dye. These dyes help better define organs and tissues in the images.

Electroencephalography (EEG) measures and records the electrical activity that is produced when brain cells communicate with each other. Special sensors, called electrodes, are attached to the outside of your head. The sensors are attached to wires that are connected to a computer, which displays the activity in wavy lines.

Hemodynamic imaging measures the brain’s blood supply (cerebral blood volume, or CBV) and flow (cerebral blood flow, or CBF). A special dye (called a “contrast”) is injected into a vein while a scanner takes a rapid succession of photographs. The photos are then used to create images of the blood flow into the tumor, allowing the doctor to see the tumor’s blood supply.

Magnetic resonance imaging (MRI) uses magnetic fields instead of X-rays to create visual images of internal structures of the body. For an MRI scan, you will lie on a table that moves through a large, circular scanner. A special dye (called a “contrast”) may be injected into a vein before the scan begins.

Magnetic resonance spectroscopy (MRS) measures metabolites (substances produced by living tissue) to produce images that represent patterns of activity in the brain. These patterns can be helpful in diagnosing specific types of brain tumors, such as low-grade gliomas, or to help determine whether a tumor is malignant. MRS may be used to supplement information obtained from other scans.

Magnetoencephalography (MEG) measures the magnetic fields emitted when nerve cells produce electrical currents during neurotransmission. This type of scan creates computer-generated images that help gauge the function of certain areas of the brain. MEG may be used to supplement information obtained from other scans.

Positron emission tomography (PET) images are not as finely detailed as those from CT or MRI but can provide helpful information to supplement those results and determine tumor grade. Cancer cells take up more glucose (a sugar substance) than normal cells. A small amount of glucose containing radioactive atoms is injected into the body. A special camera is then used to show which cancer cells have taken up the glucose.

Single photon emission computed tomography (SPECT) is similar to PET. SPECT uses a special camera to detect radioactive material that has been injected into the body. SPECT is rarely used to diagnose brain tumors but may help the doctor distinguish between low- and high-grade tumors.

Biopsy

A biopsy is the removal of tissue from a suspected tumor or removal of the entire tumor during surgery for the purpose of diagnosing the tumor. Three types of biopsy procedures generally are used for brain tumors.

Needle biopsy is a procedure in which a small hole is drilled into the skull and a hollow needle is inserted into the tumor. A sample of tissue from the tumor is collected in the hollow part of the needle. Even if a tumor is considered inoperable, it may be possible for the surgeon to perform a needle biopsy.

Open biopsy is removal of a tumor sample during a surgical procedure in which the tumor is exposed.

Stereotactic biopsy is a computer-assisted needle biopsy that uses a guidance system to identify the precise location of the tumor.

Biomarker Testing

The study of biomarkers found in body fluids, such as blood, plasma and cerebrospinal fluid, may help determine how aggressive (fast-growing) a tumor is and predict long-term survival. This type of testing is still very new and primarily performed as part of clinical trials, although it is becoming a part of clinical practice.

Biomarkers are DNA, RNA or proteins shed by brain tumor cells and are found in body fluids, such as blood, plasma and cerebrospinal fluid. Biomarkers are used to help detect, diagnose and manage some types of cancer. Although an elevated level of a biomarker may suggest the presence of cancer, this alone is not enough to diagnose cancer. Biomarkers may be prognostic or predictive. A prognostic biomarker provides information about a person’s overall cancer outcome, regardless of therapy, while a predictive biomarker gives information about the effect of a specific treatment approach. A predictive biomarker can be a target for therapy.

Several biomarkers may be involved with brain tumors:

  • 1p/19q
  • Akt3
  • ATRX
  • BRAF
  • EGFR
  • EGFRvIII
  • IDH1/IDH2
  • MGMT
  • PTEN
  • TERT

Lumbar Puncture (Spinal Tap)

A spinal tap is used to collect a sample of cerebrospinal fluid, which is examined for the presence of tumor cells, blood infection and proteins. This procedure may be used to help diagnose pineal region or meningeal tumors or central nervous system lymphoma, as well as tumors that have spread after surgery. The sample may be studied for the presence of biomarkers.

Additional Resources

 

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