Tests for Brain and Spinal Cord Tumors in Children

Brain and spinal cord tumors are usually found because of signs or symptoms a child is having. If a tumor is suspected, tests will be needed to confirm the diagnosis.

Medical history and physical exam

If your child has symptoms that suggest a brain or spinal cord tumor, the doctor will get a complete medical history, focusing on the symptoms and when they began. The doctor will also do a neurologic exam to check your child’s brain and spinal cord function, if possible. Depending on the child’s age, the exam may test reflexes, sensation, muscle strength, vision, eye and mouth movement, coordination, balance, alertness, and other functions.

If the results are abnormal, your child’s doctor may refer you to a neurologist (a doctor specializing in medical treatment of nervous system diseases) or a neurosurgeon (a surgeon specializing in nervous system diseases), who will do a more detailed exam and might order other tests.

Imaging tests

Your child’s doctors may order one or more imaging tests. These tests use x-rays, strong magnets, or radioactive substances to create pictures of internal organs such as the brain and spinal cord. The pictures may be looked at by doctors specializing in this field (neurosurgeons, neurologists, and neuroradiologists) as well as by your child’s primary care doctor.

Magnetic resonance imaging (MRI) and computed tomography (CT) scans are used most often for brain diseases. These scans will almost always show a brain or spinal cord 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 (or spinal cord).

Magnetic resonance imaging (MRI) scan

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. MRI images are usually more detailed than those from CT scans (described below). But they don't show the bones of the skull as well as CT scans and therefore might not show the effects of tumors on the skull.

MRI scans use radio waves and strong magnets (instead of x-rays) to make pictures, so they don't expose the child to radiation. A contrast material called gadolinium may be injected into a vein before the scan to help see details better.

MRI scans can take a long time, and they require a person to stay still for several minutes at a time. Some children might need medicine to help them relax or even go to sleep during the test.

Special types of MRI can be useful in some situations:

Magnetic resonance angiography (MRA) and magnetic resonance venography (MRV): These special forms of MRI may be done to look at the blood vessels in the brain, especially in and around a tumor. 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 (which are displayed in graph-like results called spectra). By comparing the results from 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 if another test shows an area still looks abnormal. The MRS can help determine if the area is remaining tumor or if it is more likely to be scar tissue.

Magnetic resonance perfusion (perfusion MRI): For this test, a contrast dye is injected quickly into a vein. Then this type of MRI can show 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 like a regular MRI, except that your child will be asked to do certain tasks (like answering simple questions or moving their fingers) to activate different areas of the brain while the scans are being done.

Diffusion tensor imaging (DTI), also known as tractography: This is a type of MRI test that can show the major pathways (tracts) of white matter in the brain. This information can be used by surgeons to help avoid these important parts of the brain when removing tumors.

Computed tomography (CT) scan

The CT scan uses x-rays to make detailed cross-sectional images of your child’s brain and spinal cord. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.

For brain and spinal cord tumors, CT scans are not used as often as MRI scans, which give slightly more detailed images and do not use radiation. Still, there are instances where CT scans may have advantages over MRI scans:

• CT scans take much less time than MRIs, which can be particularly helpful for children who have trouble staying still.
• CT scans provide greater detail of the bone structures near the tumor than MRIs do.
• CT angiography (CTA), described below, can provide better details of the blood vessels in and around a tumor than MRA in some cases.

Before the scan, your child may get an injection of a contrast dye through an IV (intravenous) line. This helps better outline any tumors that are present.

CT angiography (CTA): For this test, your child gets an injection of contrast material through an IV line while they are in the CT scanner. The scan creates detailed images of the blood vessels in the brain, which can help doctors plan surgery.

Positron emission tomography (PET) scan

For a PET scan, a radioactive substance (usually a type of sugar known as FDG) is injected into the blood. The amount of radioactivity used is very low and passes out of the body within a day or so. Because tumor cells in the body are growing quickly, they absorb larger amounts of the sugar than most other cells. A special camera is then used to create a picture of areas of radioactivity in the body. Some children might need medicine to help them relax or even go to sleep during the test.

The PET scan image 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.

Brain or spinal cord tumor biopsy

Imaging tests such as MRI and CT scans may show that a child has a brain or spinal cord tumor. But often the type of tumor can only be determined by removing a sample of it, which is called a biopsy. A biopsy may be done as a procedure on its own for diagnosis, or it may be part of surgery to treat the tumor.

In some cases (such as for many astrocytomas or brain stem gliomas), it may not be necessary or possible to biopsy the tumor safely, so the diagnosis is made based only on how the tumor looks on imaging tests.

Biopsies can be done in different ways.

Stereotactic needle biopsy

This type of biopsy may be used if imaging tests show surgery to remove the tumor might be too risky (such as with some tumors in vital areas or deep within the brain), but a sample is still needed to make a diagnosis.

Depending on the situation, the biopsy may be done with the child awake or under general anesthesia (asleep). If the child is awake, the neurosurgeon injects a local anesthetic into areas of skin over the skull to numb them. (The skull and brain itself do not feel pain.)

The biopsy itself can be done in 2 main ways:

• The most common approach is to get an MRI or CT scan, and then use either markers (each about the size of a nickel) placed on different parts of the scalp, or facial and scalp contours, to create a map of the inside of the head. An incision (cut) is then made in the scalp, and a small hole is drilled in the skull. An image-guidance system is then used to direct a hollow needle into the tumor to remove small pieces of tissue. 
• In an approach that’s used less often, a rigid frame is attached to the head. An MRI or CT scan is used along with the frame to help the neurosurgeon guide a hollow needle into the tumor to remove small pieces of tissue. This also requires an incision in the scalp and a small hole in the skull.

The biopsy samples are then sent to a pathologist (a doctor specializing in diagnosis of diseases by lab tests). 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 helps determine the best course of treatment and the prognosis (outlook).

Craniotomy (surgical or open biopsy)

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 Brain and Spinal Cord Tumors in Children) might be done to remove all or most of the tumor. (Removing most of the tumor is known as debulking.)

Small samples of the tumor are looked at right away by the pathologist while the child is still in the operating room, to get a preliminary diagnosis. This can help guide treatment, including whether further surgery should be done at that time. A final diagnosis is made a within a few days in most cases.

Lab tests of biopsy specimens

Finding out which type of tumor a child 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 tumor cells can also be important. Some tumors are now tested for these types of changes. For example:  

• Gliomas that are found to have IDH1 or IDH2 gene mutations tend to have a better outlook than gliomas without these gene mutations.
• Oligodendrogliomas whose cells are missing parts of certain chromosomes (known as a 1p19q co-deletion) are much more likely to be helped by chemotherapy than patients whose tumors do not.
• In high-grade gliomas, MGMT promoter methylation is linked with better outcomes and a higher chance of responding to chemotherapy, so it can sometimes be used to help guide treatment.
• For any type of low-grade glioma, the tumor cells might be tested for the BRAF V600E gene mutation to see if treatment with certain targeted therapy drugs might be an option.
• For medulloblastomas, changes in certain genes can be used to divide these tumors into groups, some of which have a better prognosis (outlook) than others.

You can read more about the kinds of tests that are done on biopsy or tissue samples in Testing Biopsy and Cytology Specimens for Cancer.

Lumbar puncture (spinal tap)

This test is used mainly to look for signs of cancer in the cerebrospinal fluid (CSF), which is the liquid that bathes the brain and spinal cord. For this test, the doctor first numbs an area in the lower part of the back over the spine. The doctor may also recommend that the child be given something to make them sleep so the lumbar puncture can be done more easily and safely. A small, hollow needle is then placed between the bones of the spine to withdraw some of the fluid.

The fluid is looked at under a microscope for cancer cells. The CSF can also be tested for certain substances released by some germ cell tumors.

Lumbar punctures are often used if a tumor has already been diagnosed as a type that can commonly spread through the CSF (such as a medulloblastoma). Information from the spinal tap can influence treatment.

Bone marrow aspiration and biopsy

Because some tumors (especially medulloblastomas) can spread beyond the nervous system, in some instances the doctor may recommend looking at cells in your child’s bone marrow (the soft, inner part of certain bones) to see if tumor cells have spread there.

The bone marrow aspiration and biopsy are often done at the same time. The samples are usually taken from the back of the pelvic (hip) bone, but in some cases they may be taken from other bones.

For a bone marrow aspiration, the skin over the hip and the surface of the bone is cleaned and then numbed with local anesthetic. In most cases, the child is also given other medicines to make them drowsy or even asleep during the procedure. A thin, hollow needle is then inserted into the bone, and a syringe is used to suck out (aspirate) a small amount of liquid bone marrow.

A bone marrow biopsy is usually done just after the aspiration. A small piece of bone and marrow is removed with a slightly larger needle that is pushed down into the bone. Once the biopsy is done, pressure is applied to the site to help stop any bleeding.

The specimens are then looked at under a microscope for tumor cells.

Blood and urine tests

These lab tests are rarely used to diagnose brain and spinal cord tumors, but if your child has been sick for some time 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 your child is getting chemotherapy, blood tests will be done routinely to check blood counts and to see if the treatment is affecting other parts of the body.