A number of laboratory (lab) tests are used to diagnose and monitor patients with brain tumors. Understanding these tests — what they are, how they work, and what they can and cannot show — may help you feel more comfortable and in control of the situation. If at any time you have questions about the tests ordered, be sure to ask.
Some lab tests are used to verify the presence of a brain tumor. Others are used to assess whether or not medications or treatments are working and the tumor is growing or shrinking.
Some common lab tests in patients with brain tumors include:
- Lumbar Puncture (Spinal Tap): This procedure is used to obtain a sample of cerebrospinal fluid (CSF). The sample is examined in a lab to determine if tumor cells, infection, protein, or blood is present. This information is particularly helpful in diagnosing primary central nervous system (CNS) lymphoma, a pineal region or meningeal tumor. After surgery, the presence of tumor cells in the CSF indicates that the tumor has spread. This information is used for tumor staging and helps the doctor choose the best treatment for the patient. The CSF may also be examined for the presence of known tumor markers, in addition to tumor cells, and substances that indicate the presence of a tumor.
- Myelogram: Lumbar puncture is used to inject a special dye before a myelogram. The patient is then tilted to allow the dye to mix with the CSF. This test is used primarily to diagnose a spinal tumor and to get pre-operative information for spinal tumor surgery.
- It should be noted that spinal MRI has replaced myelography for many conditions.
- Evoked-potentials: Evoked-potential testing uses small electrodes to measure the electrical activity of a nerve. This test is particularly helpful in diagnosing a vestibular schwannoma (Link to Schwannoma page)(acoustic neuroma). Evoked-potentials can also be used to monitor neurological function during the surgical removal of the tumor.
- Audiometry: A hearing test that is useful in the diagnosis of a cerebellopontine angle tumor such as the vestibular schwannoma (acoustic neuroma).
- Endocrine Evaluation: Along with scans, measurements of hormone levels in blood and/or urine samples are used to diagnose pituitary and/or hypothalamic tumors.
- Perimetry: This technique measures the size of the visual fields. The data obtained might be useful in the diagnosis of a tumor in the area of the optic chiasm, such as a pituitary tumor.
- Biomarker Research: In recent years, scientists have begun to find ways to detect tiny bits of genetic material—proteins or DNA from brain tumor cells—in bodily fluids. This field of study is called biomarker research. These tiny bits of genetic material are being explored for their potential use in the diagnosis, treatment, and monitoring of the effectiveness of medications in patients with brain tumors. To date, biomarkers have been found in blood, plasma, CSF, urine, and saliva. While the science behind these findings is advancing rapidly, their practical, everyday use in a clinical setting is still unclear and requires further investigation.
If the results of your lab test(s) are not normal, you will be sent back to the doctor for further tests and advice. Sometimes additional tests are required.
It is important to note that the information provided here is basic and does not take the place of an in-person assessment by a physician. If you have any questions about how brain tumors are diagnosed, please contact your doctor.