Common Tests

CAT Scan (Computerized Axial Tomography):

A CAT scan (also called a CT scan) is a test that uses x-rays and sophisticated computers to generate cross-sectional images (like looking at the slices of a tomato) of the inside of the head or the body. This special X-ray machine rotates 180 degrees around the head or body to obtain these types of cross-sectional images. The CT machine is shaped like a giant donut standing on its side. Your child will be asked to lie down on a sliding table and the part of the body being scanned will be placed inside the machine (like sliding through the middle of a donut). It is a painless procedure and usually takes approximately 15 to 60 minutes depending on the parts of the body being scanned and if a special dye needs to be used.

You will be notified by the CT department of any special preparations you need for your child. For further information about your child's CT scan please contact the CT department at Children's Hospital of Western Ontario. This can be obtained through the general switchboard (519 685-8484).

For general information on CAT scans, see MedLinePlus:

• printable version
• interactive version

EEG (Electroencephalogram) (ee-lek-tro-en-seh-fah-lo-gram):

The EEG is a harmless diagnostic test that picks up electrical impulses from the brain and records them in a series of wavy lines. In order to accomplish this, electrodes are placed on the scalp using gel. Having an EEG is a safe and painless procedure. This test is a primary diagnostic tool for epilepsy.

Please ask your doctor or nurse practitioner if any special preparations are necessary prior to your child having his/her EEG. You may be asked to limit your child's amount of sleep the day before or day of the EEG in order to get a more accurate EEG. This is known as a sleep-deprived EEG.

It is important for your child to continue taking his/her medications the day of the EEG. She /he may eat and drink as usual. It is helpful to bring along a bottle or toddler cup with a preferred drink as well. For example, if your child is bottle fed, a drink prior to the procedure often helps him/her settle better during the test. Please bring a favourite quiet toy, such as a stuffed animal or blanket along for comfort. You may also bring a soothing CD (no cassettes) which can be played during the EEG to help keep your child calm. You will be allowed to stay with your child during the procedure.

For more information about EEGs at the London Health Sciences Centre visit http://www.lhsc.on.ca/eeg/

MRI (Magnetic Resonance Imaging):

An MRI is a non-invasive procedure that uses a large magnet, radio waves, and a computer to collect data of the inside of the body without using radiation (x-rays). This data is fed into a computer to produce precise images and details of the body and its organs. This is helpful for diagnosing certain conditions that other tests may not be able to show. MRI staff will provide you with instructions about any special preparations or restrictions regarding eating or drinking for your child. If you have questions regarding your child's MRI scan please contact the MRI department at the London Health Sciences Centre by dialing the main switchboard (519 685-8500) and ask to be connected to the MRI department at West Campus.

For more information on MRI, see MedLinePlus:

• printable version
• interactive version

For more information on these and other diagnostic tests used for epilepsy, visit:

• Epilepsy Ontario: Children Living with Epilepsy
• Epilepsy Ontario: Diagnostic Tests

Skin Biopsy

A skin biopsy is a test that is performed specifically to look for disorders that occur at a cellular level. These are known as metabolic disorders. During a skin biopsy, a small piece of skin, about the size of a small pea, is taken from the axilla (armpit) area. The skin under the arm contains a rich supply of cells that are helpful for making a proper diagnosis.

This procedure usually takes place in the pediatric medical day unit (PMDU) or on one of the patient floors. Your child does not need a general anesthetic, however, an anesthetic cream (a local anesthetic) can be applied to the skin approximately one to two hours prior to the procedure to numb the area. Your child may experience minimal discomfort after the skin biopsy. A small Band-Aid will be placed over the site and can be removed within 24 hrs. Please observe for any signs or symptoms of infection, such as redness, drainage or swelling. Some local redness and inflammation is common for 1 - 2 days post biopsy.

For more information, talk to your health care professional.