Brain Tumors

Diagnosing Brain Tumors

To diagnose the type of brain tumor you have, your doctor will perform a thorough exam that will include questions about your medical history and symptoms, as well as a neurologic exam to assess your vision, hearing, strength and reflexes. In addition, your doctor may add any of the following tests to diagnose the tumor and determine how advanced it 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 arteries 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, enabling it to provide more details than a standard X-ray.

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 and are connected to a computer, which displays the activity in wavy lines

Hemodynamic imaging measures the brain’s blood supply and flow. The photos taken are 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.

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 or to help determine whether a tumor is malignant.

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.

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.

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. It is rarely used to diagnose brain tumors but may help the doctor distinguish between low- and high-grade tumors.

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.

Biopsy

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

  1. 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.
  2. Open biopsy is the removal of a tumor sample during a surgical procedure in which the tumor is exposed.
  3. Stereotactic biopsy is a computer-assisted needle biopsy that uses a guidance system to identify the precise location of the tumor.

Biomarker Testing

Biomarkers are substances, such as genes or molecules, which can be measured in the blood, plasma, urine, cerebrospinal fluid or other body fluids or tissues. They are produced by cancer cells or other cells of the body in response to cancer. Biomarkers are also known as tumor markers or biological markers.

Biomarkers may be prognostic, predictive or diagnostic. 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. Diagnostic biomarkers help determine the type of tumor. Some biomarkers may also help determine how aggressive (fast-growing) a tumor is and may predict long-term survival.

Although this type of testing is still very new and mostly performed in clinical trials, it is becoming a part of regular clinical practice with brain tumors. Several biomarkers have already been found to be useful in predicting treatment outcomes or long-term survival, and some cancer centers are considering working with molecular tumor boards to help doctors incorporate genomic-guided cancer care into treatment plans.

The most commonly tested biomarkers in people with brain tumors include the following:

  • 1p/19q co-deletion. Genetic changes in chromosomes 1 and 19 can occur in tumor cells (primarily for oligodendrogliomas and anaplastic oligodendrogliomas). The test for this is prognostic, predictive and diagnostic.
  • Isocitrate dehydrogenase (IDH-1). This mutated gene may be found in low-grade tumors, specifically oligodendrogliomas and astrocytomas, and secondary glioblastomas. The test for this is prognostic and diagnostic.
  • Methyl guanine methyl transferase (MGMT). This is a gene involved with DNA repair. The test is prognostic and predictive and most commonly used with glioblastomas.

Research in clinical trials is ongoing to find new biomarkers that may help diagnose brain tumors earlier or direct treatment options. In addition, knowing your biomarkers may help determine which clinical trials you may qualify for. Ask your doctor if biomarker testing is right for you.

Additional Resources

 

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