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Diagnosing brain and spinal cord cancer
Diagnosis is the process of finding the 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 reasons for a health problem before making a cancer diagnosis. Diagnostic tests for brain and spinal cord cancer are usually done when:
- the symptoms of brain or spinal cord cancer are present
- the doctor suspects brain or spinal cord cancer after talking with the person about their 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 person’s general health and to help plan treatment. Tests may include the following.
|Diagnostic tests||Staging and other tests|
The medical history is a record of present symptoms, risk factors and all the medical events and problems a person has had in the past. The medical history of a person’s family may also help the doctor to diagnose brain or spinal cord cancer.
In taking a medical history, the doctor will ask questions about:
- a personal history of:
- radiation exposure
- inherited conditions
- conditions or medications that weaken the immune system
- a family history of:
- a brain or spinal cord tumour
- factors that may increase the risk of developing a brain or spinal tumour
- other cancers
- signs and symptoms that may suggest brain or spinal cord cancer
A physical examination allows the doctor to look for any signs of brain or spinal cord cancer. The doctor may also do a neurological examination and vision and hearing tests if a brain or spinal cord tumour is suspected.
- neurological examination
- balance and coordination
- motor skills
- muscle strength
- response to pain
- awareness of surroundings
- judgment and reasoning
- ability to calculate
- language skills
- vision tests
- visual field
- eye movement
- hearing tests
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. MRI is considered the best way to look for tumours in the areas of the brain and spinal cord. MRI usually provides more detailed images of soft tissues than CT scans, but CT scans produce better images of the bones in the skull. The choice between a CT scan, MRI or other types of imaging depends on what tissues a doctor wants to see. Other special types of MRIs might be done.
- magnetic resonance angiography (MRA)
- MRA is used to look at the structure of blood vessels in the brain.
- It is useful in planning the operation before surgery.
- magnetic resonance spectroscopy (MRS)
- MRS highlights some features of brain tumours that are not clearly seen by MRI.
- It may help doctors determine the possible tumour type.
- It is used after treatment to see if an abnormal area is a tumour or only scar tissue.
- magnetic resonance perfusion (perfusion MRI)
- Perfusion MRI images show the amount of blood going though different parts of the brain.
- It can give doctors an idea of how fast a tumour is growing and help them determine the best place to take a biopsy.
- It is used after treatment to see if an abnormal area is a tumour or simply scar tissue.
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. CT scans are not used as often as MRI scans to diagnose or stage brain cancer, but are useful in some cases. They may be used:
- to provide better detail of the bone structures near the tumour
- when MRI is not an option (for example, with people who are very overweight or are afraid of enclosed spaces)
CT angiography (CTA) creates detailed images of blood vessels in the brain, which can help the surgeon plan the operation.
A PET scan uses very weak 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. It is used:
- to determine if abnormal areas seen on an MRI or CT scan are likely to be cancerous
- after treatment to see if an abnormal area is a tumour or scar tissue
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 following biopsies may be used for brain or spinal cord cancer.
Surgical (open) biopsy
If the tumour appears to be treatable with surgery based on the imaging tests, a biopsy sample will be taken during surgery to remove the tumour.
- During the operation, called a craniotomy, part of the skull is removed so the surgeon can reach the tumour. All or most of the tumour is removed.
- Small samples of the tumour are examined while the person is still in the operating room. This first diagnosis can help guide treatment, including whether further surgery should be done at that time.
- The bone that was removed from the skull to make an opening is usually replaced after the tumour is taken out.
Endoscopic third ventriculoscopy
An endoscopic third ventriculoscopy (ETV) uses an endoscope to explore the fluid-filled chambers (ventricles) of the brain.
- The endoscope can be used to take a biopsy sample or remove tumours inside the ventricles.
Stereotactic (closed) biopsy
Stereotactic biopsy may be used for tumours that likely can’t be removed by surgery (for example, tumours that are in vital areas or deep within the brain).
- A local anesthetic is used to freeze the scalp. Some people may be under general anesthesia.
- A special frame is fastened to the head to hold it in place to ensure that the surgeon can accurately target the tumour.
- The surgeon makes a cut in the scalp and drills a small hole in the skull.
- An MRI or CT scan is usually used along with the frame to help the surgeon guide a hollow needle into the tumour and remove tissue samples for biopsy.
A lumbar puncture is a biopsy procedure that removes a small amount of cerebrospinal fluid (CSF) for examination under a microscope. During the procedure, the doctor inserts a needle into the spine of the lower back and withdraws CSF from the space where it circulates within the spinal cord. The pathologist looks for any cancer cells in the CSF.
Lumbar punctures are not generally done to diagnose brain and spinal cord cancer, but may be done after a diagnosis of certain types of brain tumours that are known to spread via the CSF.
Blood tests are not used to diagnose brain or spinal cord cancer. However, they are routinely done to provide a baseline before any planned treatment. They can provide helpful information about:
- a person’s general health
- how some other organs, such as the liver and kidneys, are functioning
- other medical conditions
- the potential risks of treatment
Blood tests that are used with brain and spinal cord cancer are:
- 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.
Urinalysis is a test that measures substances found in urine, such as electrolytes, hormones or other waste products. Urine tests are not used to diagnose brain and spinal cord cancer. However, they may provide helpful information about a person’s general health, how some other organs are functioning and other medical conditions.
An x-ray uses small doses of radiation to make an image of the body’s structures on film. A chest x-ray may be done after a brain tumour is found because tumours in the lung often spread to the brain. Spine x-rays may be done if doctors think the cancer may have spread (metastasized) to the space around the spinal cord.
During angiography, dye is injected into the bloodstream and x-rays are taken to map out the size and shape of blood vessels. It is used to look at the blood vessels and the flow of blood in the brain. In recent years, angiography has been mostly replaced by other tests, such as magnetic resonance angiography and CT angiography.
During myelography, a dye is injected into the space between the meninges of the spinal cord, usually by way of a lumbar puncture. The x-ray produced outlines the spinal cord and nerve roots. A CT scan (CT myelography) makes images of the spinal cord structures on film. It is used to:
- locate a spinal cord tumour
- identify how much the tumour has invaded the spinal cord and nerves
In recent years, myelography and CT myelography have been mostly replaced by magnetic resonance imaging (MRI).
I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.
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