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Diagnosing childhood brain and spinal cord cancer
Diagnosis is the process of finding the underlying cause of a health problem. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other possible reasons for a health problem before making a cancer diagnosis. Diagnostic tests for childhood brain and spinal cord cancer are usually done when:
- the symptoms of brain and spinal cord cancer are present
- the doctor suspects brain or spinal cord cancer after talking with the child and their parents about the child’s health and completing a physical examination
Many of the same tests used to initially diagnose cancer are also used to determine the stage (how far the cancer has progressed). The doctor may also order other tests to check the child's general health and to help plan treatment. Tests may include the following:
The medical history is a record of present symptoms, risk factors and all the medical events and problems a child has had in the past. The medical history of a child's family may also help the doctor to diagnose brain and spinal cord cancer.
In taking a medical history, the doctor will ask questions about:
- a personal history of
- inherited genetic conditions
- exposure to radiation to the head
- signs and symptoms the child is experiencing that may suggest brain and spinal cord cancer
A physical examination allows the doctor to look for any signs of brain and spinal cord cancer. When brain or spinal cord cancer is suspected, the doctor will perform a neurological exam to check the child's brain function and find out which part of the brain might be affected. The age of the child will determine what aspects of neurological function can be assessed. During a neurological exam, the doctor may check the child's:
- mental status
- Does the child know the time of day, the day of the week and where the child is?
- Can the child recall yesterday's supper, a recent holiday or event, or a list of objects displayed earlier in the appointment?
- Can the child pay attention to the doctor during the appointment?
- cranial nerve function
- Can the child follow an object with the eyes?
- Do both eyes close equally?
- Is the child's smile equal on both sides?
- Can the child turn the head and shrug the shoulders?
- Can the child stick out the tongue?
- Can the child hear equally well with each ear?
- sensory function
- Can the child tell the difference when touching different objects, such as a soft cotton ball and a stone?
- Can the child tell the difference between varying tastes and smells?
- muscle function
- Can the child grip the doctor's hands with equal strength?
- Can the child push both arms or both legs against the doctor with equal strength?
- Can the child hold both arms straight out and steady for 10 seconds? Can the child do this with both eyes closed?
- coordination and gait
- Can the child balance on the toes? On one foot? On both feet with the eyes closed?
- Can the child walk a straight line?
- Can the child touch the fingers to the nose?
- The doctor will check if reflexes in the arms, legs and feet are equal and strong by gently tapping on specific points with a rubber hammer.
Blood tests are not usually done to definitively diagnose brain or spinal cord cancer, but they may help to determine the type of brain or spinal cord cancer. Doctors will routinely do blood tests to help assess the child's overall health and fitness for treatment.
- A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets.
- Blood chemistry tests measure certain chemicals in the blood and show how well certain organs, such as the liver and kidneys are working.
- Tumour marker tests check for substances – usually proteins – in the blood that may help the doctor determine the type of tumour a child has.
- Alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) are 2 tumour markers that may be elevated if the child has a germ cell or a pineal tumour
MRI uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-dimensional pictures. Sometimes a dye is injected into the child's vein to create a better picture. MRI is considered the best way to look at tumours in the brain and spinal cord areas.
MRI examination requires that the child lie still for long periods of time. Young children may need a general anesthetic to keep them from moving and ensure that the scan can be done properly.
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of tumours, organs, tissues, bones and blood vessels inside the body. A computer turns the images into pictures. Sometimes a dye is injected into a child's vein to make structures easier to see in the pictures. CT scans have been largely replaced by MRIs, which provide a more detailed image. However, a CT scan takes much less time to perform and is preferred for children who cannot lie still. A CT scan may also help doctors determine if an MRI scan needs to be done.
An angiogram is sometimes done to check the blood vessels in the area of the brain or spinal cord tumour. A special dye is injected into the child's vein and then x-rays are taken of the child's brain or spinal cord. Angiograms have largely been replaced by MRIs.
A PET scan uses radioactive materials (radiopharmaceuticals) to detect changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3-dimensional colour images of the area being scanned. PET scans may help doctors tell the difference between cancerous and non-cancerous areas, but are not often used in childhood brain and spinal cord cancer.
During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample. The biopsies that could be used for brain and spinal cord cancer are:
- surgical (open) biopsy
- The surgeon takes a biopsy sample during surgery to remove the tumour.
- A part of the skull is removed so the surgeon can reach the tumour and remove it.
- The bone is often replaced after the tumour is removed.
- stereotactic (closed) biopsy
- The doctor inserts a thin probe into the tumour through a small hole in the skull to collect a biopsy sample.
- A special frame holds the child's head in place.
- An MRI or CT scan is done to guide the surgeon to the tumour.
During a lumbar puncture, the doctor inserts a needle into the spine to collect a small amount of cerebrospinal fluid (CSF) for examination under a microscope. A lumbar puncture may be done to see if a brain tumour has spread to the spinal cord.
A bone scan uses bone-seeking radioactive materials (radiopharmaceuticals) and a computer to create a picture of the bones. It is often used to see if a certain brain tumour, called a medulloblastoma, has spread to any bones in the body.
During a bone marrow aspiration and biopsy, the doctor inserts a special needle into one of the larger bones, such as the hip. The doctor uses the needle to collect a sample of bone marrow, blood and a small piece of bone. A bone marrow aspiration and biopsy is done to see if a certain brain tumour, called a medulloblastoma, has spread to the bone or bone marrow.