Brain and spinal cord tumors are usually found because of signs or symptoms a person is having. If a tumor is suspected, tests will be needed to confirm the diagnosis.
If signs or symptoms suggest you might have a brain or spinal cord tumor, your doctor will ask about your medical history, focusing on your symptoms and when they began. The doctor will also check your brain and spinal cord function by testing things like your reflexes, muscle strength, vision, eye and mouth movement, coordination, balance, and alertness.
If the results of the exam are abnormal, you may be referred to a neurologist (a doctor who specializes in medical treatment of nervous system diseases) or a neurosurgeon (a doctor who specializes in surgical treatment of nervous system diseases), who will do a more detailed neurologic exam and may order other tests.
Your doctor may order one or more imaging tests. These tests use x-rays, strong magnets, or radioactive substances to create pictures of the brain and spinal cord.
Magnetic resonance imaging (MRI) and computed tomography (CT) scans are used most often to look for brain diseases. These scans will almost always show a brain tumor, if one is present. Doctors can often also get an idea about what type of tumor it might be, based on how it looks on the scan and where it is in the brain.
MRI scans are very good for looking at the brain and spinal cord and are considered the best way to look for tumors in these areas. The images they provide are usually more detailed than those from CT scans (described below). But they do not pick up the bones of the skull as well as CT scans and therefore may not show the effects of tumors on the skull.
MRI scans use radio waves and strong magnets (instead of x-rays) to make pictures. A contrast material called gadolinium may be injected into a vein before the scan to help see details better.
Special types of MRI can be useful in some situations:
Magnetic resonance angiography (MRA) and magnetic resonance venography (MRV): These special types of MRI may be used to look at the blood vessels in the brain. This can be very useful before surgery to help the surgeon plan an operation.
Magnetic resonance spectroscopy (MRS): This test can be done as part of an MRI. It measures biochemical changes in an area of the brain (displayed in graph-like results called spectra, although basic images can also be created). By comparing the results for a tumor to that of normal brain tissue, it can sometimes help determine the type of tumor (or how quickly it is likely to grow), although a biopsy of the tumor is often still needed to get an accurate diagnosis. MRS can also be used after treatment to help determine if an area that still looks abnormal on another test is remaining tumor or if it is more likely to be scar tissue.
Magnetic resonance perfusion: For this test, also known as perfusion MRI, a contrast dye is injected quickly into a vein. A special type of MR image is then obtained to look at the amount of blood going through different parts of the brain and tumor. Tumors often have a bigger blood supply than normal areas of the brain. A faster growing tumor may need more blood.
Perfusion MRI can give doctors an idea of the best place to take a biopsy. It can also be used after treatment to help determine if an area that still looks abnormal is remaining tumor or if it is more likely to be scar tissue.
Functional MRI (fMRI): This test looks for tiny blood flow changes in an active part of the brain. It can be used to determine what part of the brain handles a function such as speech, thought, sensation, or movement. Doctors can use this to help determine which parts of the brain to avoid when planning surgery or radiation therapy.
This test is similar to a standard MRI, except that you will be asked to do specific tasks (such as answering simple questions or moving your fingers) while the scans are being done.
A CT scan uses x-rays to make detailed cross-sectional images of your brain and spinal cord (or other parts of the body). Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.
CT scans are not used as often as MRI scans when looking at brain or spinal cord tumors, but they can be useful in some cases. They may be used if MRI is not an option (such as in people who are very overweight or people who have a fear of enclosed spaces). CT scans also show greater detail of the bone structures near the tumor.
As with MRI, you may get an injection of a contrast dye through an IV (intravenous) line before the scan (although a different dye is used for CT scans). This helps better outline any tumors that are present.
CT angiography (CTA): For this test, you are injected with a contrast material through an IV line while you are in the CT scanner. The scan creates detailed images of the blood vessels in the brain, which can help doctors plan surgery. CT angiography can provide better details of the blood vessels in and around a tumor than MR angiography in some cases.
For a PET scan, you are injected with a slightly radioactive substance (usually a type of sugar known as FDG) which collects mainly in tumor cells. A special camera is then used to create a picture of areas of radioactivity in the body. The picture is not as detailed as a CT or MRI scan, but it can provide helpful information about whether abnormal areas seen on other tests (such as MRIs) are likely to be tumors or not. This test is more likely to be helpful for fast-growing (high-grade tumors) than for slower-growing tumors.
This test is also useful after treatment to help determine if an area that still looks abnormal on an MRI scan is remaining tumor or if it is more likely to be scar tissue. Remaining tumor might show up on the PET scan, while scar tissue will not.
A chest x-ray might be done to look for tumors in the lungs if a tumor is found in the brain. This is because in adults, most tumors in the brain actually have started in another organ (most often the lung) and then spread to the brain. This test can be done in a doctor’s office, in an outpatient radiology center, or in a hospital.
Imaging tests such as MRI and CT scans may show an abnormal area that is likely to be a brain or spinal cord tumor. But these scans can’t always tell exactly what type of tumor it is. Often this can only be done by removing some of the tumor tissue in a procedure called a biopsy. A biopsy may be done as a procedure on its own, or it may be part of surgery to remove the tumor.
Sometimes, a tumor may look so characteristically obvious on an MRI scan (for example, clearly looking like an astrocytoma) that a biopsy is not needed, especially if the tumor is in a part of the brain that would make it hard to biopsy (such as the brain stem). In rare cases a PET scan or MR spectroscopy may give enough information so that a biopsy is not needed.
The 2 main types of biopsies for brain tumors are:
This type of biopsy may be used if, based on imaging tests, surgery to remove the tumor might be too risky (such as with some tumors in vital areas, those deep within the brain, or other tumors that probably can’t be removed safely with surgery) but a sample is still needed to make a diagnosis.
The patient may be asleep (under general anesthesia) or awake during the biopsy. If the patient is awake, the neurosurgeon injects a local anesthetic into areas of skin above the skull to numb them. (The skull and brain do not feel pain.)
The biopsy itself can be done in two main ways:
The removed tissue is sent to a pathologist (a doctor specializing in diagnosis of diseases by lab tests). Sometimes it might need to be looked at by a neuropathologist, a pathologist who specializes in nervous system diseases. The pathologist looks at it under a microscope (and might do other lab tests) to determine if the tumor is benign or malignant (cancerous) and exactly what type of tumor it is. This is very important in determining a person's prognosis (outlook) and the best course of treatment. A preliminary diagnosis might be available the same day, although it often takes at least a few days to get a final diagnosis.
If imaging tests show the tumor can likely be treated with surgery, the neurosurgeon may not do a needle biopsy. Instead, an operation called a craniotomy (described in Surgery for Adult Brain and Spinal Cord Tumors) might be done to remove all or most of the tumor. (If removing all of the tumor would likely damage nearby important structures, removing most of the tumor, known as debulking, might be done.)
For a preliminary diagnosis, small samples of the tumor are looked at right away by the pathologist while the patient is still in the operating room. This can help guide treatment, including whether further surgery should be done at that time. A final diagnosis is made within a few days in most cases.
You can read more about the kinds of tests done on biopsy or tissue samples in Testing Biopsy and Cytology Specimens for Cancer.
Finding out which type of tumor someone has is very important in helping to determine their outlook (prognosis) and treatment options. But in recent years, doctors have found that changes in certain genes, chromosomes, or proteins within the cancer cells can also be important. Some tumors are now tested for these types of changes. For example:
Lab tests looking for other gene or chromosome changes might also be done.
This test is used mainly to look for cancer cells in the cerebrospinal fluid (CSF), the liquid that surrounds the brain and spinal cord. For this test, you lie on your side on a bed or exam table with your knees up near your chest. The doctor first numbs an area in the lower part of the back near the spine. A small, hollow needle is then placed between the bones of the spine to withdraw some of the fluid.
This fluid is sent to a lab to be looked at for cancer cells. Other tests may be done on the fluid as well.
Lumbar punctures are usually very safe, but doctors have to make sure the test does not result in a large drop in fluid pressure inside the skull, which could possibly cause serious problems. For this reason, imaging tests such as CT or MRI scans are done first.
Lumbar punctures usually aren’t done to diagnose brain tumors, but they may be done to help determine the extent of a tumor by looking for cancer cells in the CSF. They are often used if a tumor has already been diagnosed as a type that can commonly spread through the CSF, such as an ependymoma. Lumbar punctures are particularly important in people with suspected brain lymphomas because lymphoma cells often spread into the CSF.
These lab tests rarely are part of the actual diagnosis of brain and spinal cord tumors, but they may be done to check how well the liver, kidneys, and some other organs are working. This is especially important before any planned surgery. If you are getting chemotherapy, blood tests will be done routinely to check blood counts and to see if the treatment is affecting other parts of your body.
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National Cancer Institute Physician Data Query (PDQ). Adult Central Nervous System Tumors Treatment. 2020. Accessed at www.cancer.gov/types/brain/hp/adult-brain-treatment-pdq on February 11, 2020.
Wong ET, Wu JK. Overview of the clinical features and diagnosis of brain tumors in adults. UpToDate. 2020. Accessed at https://www.uptodate.com/contents/overview-of-the-clinical-features-and-diagnosis-of-brain-tumors-in-adults on February 11, 2020.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Central Nervous System Cancers. V.3.2019. Accessed at www.nccn.org/professionals/physician_gls/pdf/cns.pdf on February 13, 2020.
Last Revised: May 5, 2020