Tests

Tests may include:

• MRI scan —a test that uses magnetic fields to make computerized pictures of the brain
• CT scan —a type of x-ray that uses a computer to make pictures of structures inside the body
• Angiography —a test that uses x-rays to make pictures of blood vessels after injection of contrast material into your blood circulation
• Biopsy —removal of a sample of brain tissue to test for cancer cells
• Stereotactic biopsy—use of a computer-assisted CT or MRI scan to locate the tumor and take a biopsy
  • To take a biopsy, the doctor drills a small hole in the skull, inserts a needle guided by stereotaxis (guiding the biopsy using three dimensional techniques) and withdraws a sample of tumor tissue.
• PET and SPECT scans—tests that detect the level of metabolic activity in the brain and other organs by tracking a radioactive substance that is injected into the bloodstream
  • These tests are far from routine and are currently not used in the initial evaluation. These may be used to supplement information from the CT and MRI scans.
• Electroencephalogram (EEG)—a noninvasive test used to evaluate brain function or disorders

CT Scan of the Head Copyright © Nucleus Medical Media, Inc.

Sometimes tests are combined. For instance, certain contrast agents can be injected into the bloodstream that will produce better images with CT or MRI scanning, thus combining angiography with computerized imaging. An example of this test is a CTA (CT angiogram) or MRA (magnetic resonance angiogram).

Characteristics of Tumors

Some important characteristics of a tumor are:

• Type of tumor
• Location
• Size

These factors determine the symptoms, prognosis, and treatment. It is important whether the tumor originated in the nervous system or spread there from somewhere else in the body.

Tumors are graded according to numerous features. All cancers are graded to identify the most promising treatment and to determine their prognosis. In some cases, a biopsy cannot be safely performed. The doctors then estimate what type of brain tumor exists and make treatment plans accordingly.

Grading

Malignant brain tumors are graded on a numerical scale using one of several systems. The preferred grading system is the World Health Organization’s (WHO). The tumor grades help predict the rate of tumor growth, its ability to spread, and in turn prognosis. Astrocytomas are graded on a scale of I through IV as follows:

• Grades I—a tumor that has well-defined borders; primarily found in children
• Grade II—an invasive tumor that can grow and progress to a higher grade
• Grades III and IV—high-grade tumors, the most common form found in adults; can grow rapidly and can spread throughout the brain and spinal cord; aggressive treatment is needed
  • Grade III astrocytomas are also known as anaplastic astrocytomas.
  • Grade IV astrocytomas are also known as glioblastoma multiforme.

Patient Factors

The two most important factors that predict how well someone may do are the patient’s age and performance status. Younger patients generally do better, as do patients who have very few symptoms associated with their tumor. Doctors always consider a patient’s age and performance status when they plan treatment.