Pediatric brain tumors are diagnosed when a child exhibits symptoms and signs of brain tumors in children that may indicate an abnormality in the central nervous system. There are multiple tests that are conducted before a definite diagnosis can be made .
If the physician suspects that there may be a brain tumor, the first thing the doctor will do is obtain a complete medical history starting with the type and timeline of the symptoms. Doctors will also conduct a neurological exam which involves:
- testing motor skills,
- senses including the ability to move the eye and the mouth,
- balance and
If the results are not normal, then the physician will refer the patient to either a neurologist or a neuro-oncologist who will conduct the rest of the diagnosis .
Magnetic resonance imaging (MRI) or computed tomography will show a brain tumor, if there is one, in most cases. MRI scans, which use radio waves and magnets, are considered as the best way to look for brain tumors as they contain more details than CT scans and don’t image bones, just the brain matter.
Sometimes, a chemical called gadolinium may be inserted into the child as it helps increase contrast in the images. This process can take up to an hour.
Magnetic resonance angiography is a special type of MRI that is used specifically to look at blood vessels in the brain.
- Magnetic resonance spectroscopy,
- Magnetic resonance perfusion and
- functional MRI
are all variations of the original MRI method that look at different things in the brain in order to obtain more information about the type of tutor present .
Computed tomography scans, or CT scans, use x-rays to look at the details of the brain and the spinal cord. CT scans can provide very detailed images but they are not used as often as MRI scans as CT scans use radiation which can be harmful to the child. Some advantages of CT scans include:
- less time,
- greater detail of how bones may be impacted by the tumor, and
- a CT angiography can allow imaging of blood vessels around the tumor.
Similar to an MRI scan, a contrast dye may sometimes be used .
Positron emission tomography (PET) scan is another type of imaging method which requires the injection of a radioactive substance into the blood vessel. The radioactivity is not dangerous as it can have very low activity and passes through the body in 24 hours. While not used as often as CT or MRI, the PET scan can provide important information such as whether the abnormal areas seen on the images are actually tumors, which is particularly useful for post-surgical analysis .
While the imaging tests outlined above are great in terms of determining whether a child has a brain tumor, the type of tumor is hard to discern and therefore, biopsies are the main method of diagnosing type of tumor.
The biopsy can be conducted on its own as a removal of tissue for the sole purpose of diagnosis, or it can be done during surgery when the surgeon is removing part of the tumor. A doctor called a pathologist then looks at the biopsy sample under a microscope and then determines whether the tumor is non-cancerous or cancerous as well as the type of tumor .
There are four different types of biopsies:
- stereotactic needle biopsy,
- spinal tap,
- bone marrow aspiration.
Stereotactic needle biopsy is conducted when the tumor is too risky to be operated on but a sample is still needed to make a definite diagnosis. In this case, a small cut is made in the scalp and a small hole is drilled into the skull and a MRI or CT scan is used to guide the surgeon to the tumor to remove a small piece .
A craniotomy is conducted when the imaging tests show that the tumor is treatable with surgery, in which case the surgeon will go ahead and remove the whole tumor. A small piece of the tumor is used to make the diagnosis, which can help determine whether more surgery is needed for the patient .
A spinal tap is conducted to look at whether cancer cells have invaded the CSF or the cerebrospinal fluid, which is present in the brain and the spinal cord. This involves a small hollow needle being inserted between the spinal bones to withdraw the fluid. This biopsy helps determine whether the tumor has spread to the spinal fluid .
Bone marrow aspiration is conducted in the case of certain tumors that are more like to have spread outside of the nervous system. This involves looking at cells in the bone marrow by inserting a thin hollow needle into the bone to suck out the liquid bone marrow. This biopsy helps determine whether the tumor has metastasized beyond the brain .