A cranial CT scan of the head is a diagnostic tool used to create detailed pictures of the skull, brain, paranasal sinuses, and eye sockets. CT stands for “computed tomography,” but is known by a variety of names, including brain scan, head scan, skull scan, paranasal sinus scan, and CAT scan.
The cranial CT scan is noninvasive and is usually suggested first to avoid more invasive and painful procedures.
The pictures created by the cranial CT scan are far more detailed than regular X-rays and can help in the diagnosis of injuries, stroke, bleeding, tumors, infections, birth defects, fluid buildup, and bone abnormalities.
Your doctor may order a cranial CT scan if you have had an injury or display any of these symptoms with no apparent cause:
- behavioral changes or changes in thinking
- hearing loss
- vision loss
- muscle weakness or numbness and tingling
- speech difficulty
- difficulty swallowing
A cranial CT scan can also be used to guide other procedures such as surgery or biopsy.
The cranial CT scanner takes a series of X-rays. A computer then puts these X-ray images together to create detailed pictures of the head to assist your doctor in diagnosing your condition.
The procedure is usually done in a hospital or outpatient center. On the day of the procedure:
- You must remove jewelry and other metal objects that can damage the scanner or interfere with the X-rays. You may be asked to wear a hospital gown.
- You will lie on a narrow table either face up or face down, depending on the reasons for your CT scan.
- It is very important that you remain completely still during the exam. Even a little movement can blur the images. If required, your doctor may suggest a sedative to keep your body still. Some people find the CT scanner stressful or claustrophobic. Your doctor may also suggest a sedative to keep you calm during the procedure.
- The table will slowly slide so that your head is inside the scanner.
- In some cases you may be asked to hold your breath for a short period.
- The scanner’s X-ray beam will rotate around your head, creating a series of images of your head taken at different angles. The individual images are called “slices.”
- The images can be seen immediately on a monitor, stored for later viewing, and printed. Stacking the slices together can create three-dimensional images.
- For your security, the CT scanner has a microphone and speakers for two-way communication with the scanner operator.
- It should take only about 15 minutes to complete your scan.
Cranial CT Scan for Children
If your infant or toddler must have a cranial CT scan, a sedative may be recommended to help your child remain calm and keep still.
Contrast dye helps highlight some areas better on the images. For example, it can highlight and emphasize blood vessels, intestines, or other areas. The dye is given through an IV in your arm or hand. Often, images will be taken first without contrast, then again with contrast.
Your doctor may direct you not to eat or drink for several hours prior to the test if you are to receive contrast. This can vary according to your particular medical condition, so be sure to ask your doctor for specific instructions for your CT scan.
Use of contrast dye is not always necessary—it depends on what your doctor is looking for.
The scanner table is very narrow. If you weigh more than 300 pounds, ask if there is a weight limit for the CT scanner table.
Be sure to tell your doctor if you are pregnant. X-rays of any kind are not recommended for pregnant women.
If contrast dye will be used, there are some extra precautions to be aware of. For example, special measures must be taken for people on the diabetes medicine metformin (Glucophage), so be sure to inform your doctor if you take this drug. Also tell your doctor if you have ever suffered an adverse reaction to contrast dye.
The CT scan itself is a painless procedure. Some people feel uncomfortable on the hard table or have difficulty remaining still.
If you are given contrast dye, you may feel a slight burning when it enters your vein. Some people experience a metal taste in their mouth and a warm sensation throughout their body. These reactions are normal and generally last less than a minute.
CT scans do expose you to some radiation. Doctors generally agree that the risks are low compared to the potential risk of not being diagnosed with a dangerous health problem. The risk from a single scan is small, but the risk increases if you have many X-rays or CT scans over time. Newer scanners may expose you to less radiation than older models.
Tell your doctor if you’re pregnant. To avoid exposing your baby to radiation, your doctor may be able to use other tests, such as magnetic resonance imaging (MRI) or ultrasound, which do not use radiation.
Discuss the radiation risk of cranial CT scan with your doctor prior to the test so you can assess the potential risks and benefits for your medical condition.
Allergic Reaction to Contrast
Inform your doctor prior to the scan if you have ever had an allergic reaction to contrast dye.
The contrast dye commonly contains iodine and may cause nausea, vomiting, rash, hives, itching, or sneezing in people who are allergic to iodine. To help with these symptoms, steroids or antihistamines may be given prior to the injection of the dye. People who have diabetes or kidney disease may need to take extra fluids after the test to help flush the iodine from the body.
In very rare cases, contrast dye causes anaphylaxis, a whole-body allergic reaction that can be life threatening. Notify the scanner operator immediately if you have trouble breathing.
Note: CT scanners have an intercom system that allows two-way conversation.
A radiologist will interpret the results and send a report to your doctor. The scans are stored electronically for future reference. Your doctor will discuss the radiologist’s report with you.
Some conditions that can be identified through cranial CT scan include:
- brain aneurysm
- bleeding in the brain abscesses, hemorrhage
- brain tumor or other mass
- brain infection or swelling
- abnormal blood vessels (arteriovenous malformation)
- atrophy of brain tissue
- fluid buildup in the skull (hydrocephalus)
- fracture or injury to head, face, or skull
- birth defects
- abnormalities of the bone of the skull