A cranial CT scan of the head is a diagnostic tool used to create detailed pictures of the skull, brain, paranasal sinuses, ventricles, and eye sockets. CT stands for “computed tomography,” but is known by a variety of names, including brain scan, head scan, skull scan, sinus scan, and CAT scan.
A cranial CT scan is noninvasive and is usually suggested to investigate various neurological symptoms before turning to more invasive and painful procedures.
The pictures created by a cranial CT scan are far more detailed than regular X-rays. They can help diagnose a range of conditions, including:
- birth defects
- fluid buildup
- 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:
- seizures (especially recent onset)
- sudden 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.
A 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. These images help your doctor make a diagnosis.
The procedure is usually done in a hospital or outpatient imaging center. It should take only about 15 minutes to complete your scan.
On the day of the procedure, you must remove jewelry and other metal objects. They can damage the scanner and interfere with the X-rays.
You’ll probably be asked to change into a hospital gown. You’ll lie on a narrow table either face up or face down, depending on the reasons for your CT scan. It’s very important that you remain completely still during the exam. Even a little movement can blur the images.
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. 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 from different angles. The individual images are called “slices.” Stacking the slices together can create three-dimensional images.
Images can be seen immediately on a monitor. They will be stored for later viewing and printed. For your security, the CT scanner has a microphone and speakers for two-way communication with the scanner operator.
Cranial CT Scan for Children
Your child’s doctor may recommend a sedative to help them 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, and other areas. The dye is given through an IV in your arm or hand.
Often, images are first taken first without contrast, then again with contrast. However, use of contrast dye isn’t always necessary. It depends on what your doctor is looking for.
Your doctor may direct you not to eat or drink for several hours before the test if you’re going to receive contrast dye. This depends on your particular medical condition. Ask your doctor for specific instructions for your CT scan.
The scanner table is very narrow. Ask if there is a weight limit for the CT scanner table if you weigh more than 300 pounds. Be sure to tell your doctor if you’re pregnant. X-rays of any kind are not recommended for pregnant women.
There are some extra precautions to be aware of if contrast dye will be used. For example, special measures must be taken for people on the diabetes medicine metformin (Glucophage). Be sure to let your doctor know if you take this drug. Also tell your doctor if you’ve 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.
You may feel a slight burning when the contrast dye enters your vein. Some people experience a metal taste in their mouths and a warm sensation throughout their bodies. These reactions are normal and generally last less than a minute.
CT scans 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. Your doctor may be able to avoid exposing your baby to radiation by using other tests. These may include a magnetic resonance imaging (MRI) or ultrasound, which does not use radiation.
Discuss the risk of cranial CT scan with your doctor before the test so you can assess the potential risks and benefits for your medical condition.
Allergic Reaction to Contrast
Tell your doctor before the scan if you’ve 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. You may be given steroids or antihistamines to help with these symptoms before you receive the dye injection. You may need to drink extra fluids after the test to help flush the iodine from the body if you have diabetes or kidney disease.
In very rare cases, contrast dye can cause anaphylaxis, a whole-body allergic reaction that can be life-threatening. Notify the scanner operator immediately if you have trouble breathing.
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, or hemorrhage
- brain tumor or other mass
- brain infection (e.g., abscess) 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
- abnormalities of the bone of the skull
You should be able to return to your normal routine after the test. Your doctor may give you special instructions if contrast was used in your test.
Your doctor will go over your results with you once they’re ready. Depending on the results, your doctor might order more tests.