Definition of Cranial CT scan:

A cranial computed tomography (CT) scan uses many x-rays to create pictures of the head, including the skull, brain, eye sockets, and sinuses.

See: Computed tomography

How the test is performed:

You will be asked to lie on a narrow table that slides into the center of the CT scanner.

Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam without stopping.)

A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the head area can be created by stacking the slices together.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

Generally, complete scans take only a few minutes. The newest scanners can image your entire body, head to toe, in less than 30 seconds.

How to prepare for the test:

Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast helps certain areas show up better on the x-rays.

• Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.
• Let your doctor know if you have ever had a reaction to contrast. You may need to take medications before the test in order to safely receive this substance.
• Before receiving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions.

If you weigh more than 300 pounds, find out if the CT machine has a weight limit. Too much weight can cause damage to the scanner's working parts.

You will be asked to remove jewelry and wear a hospital gown during the study.

How the test will feel:

The x-rays produced by the CT scan are painless. Some people may have discomfort from lying on the hard table.

Contrast given through a vein may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the test is performed:

A cranial CT scan is recommended to help diagnose or monitor the following conditions:

• Birth (congenital) defect of the head or brain
• Brain infection
• Brain tumor
• Buildup of fluid inside the skull (hydrocephalus)
• Craniosynostosis
• Injury (trauma) to the head and face
• Stroke or bleeding in the brain

A cranial CT may also be done to look for the cause of:

• Changes in thinking or behavior
• Fainting
• Headache, when certain other signs or symptoms are present
• Hearing loss (in some patients)
• Symptoms of damage to part of the brain, such as vision problems, muscle weakness, numbness and tingling, hearing loss, speaking difficulties, or swallowing problems