What is a cranial CT scan?

A cranial CT scan is a diagnostic tool used to create detailed pictures of features inside your head, such as your skull, brain, paranasal sinuses, ventricles, and eye sockets. CT stands for computed tomography, and this type of scan is also referred to as a CAT scan. A cranial CT scan is known by a variety of names as well, including brain scan, head scan, skull scan, and sinus scan.

This procedure is noninvasive, meaning it doesn’t require surgery. It’s usually suggested to investigate various symptoms involving the nervous system before turning to invasive 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:

  • abnormalities of the bones of your skull
  • arteriovenous malformation, or abnormal blood vessels
  • atrophy of brain tissue
  • birth defects
  • brain aneurysm
  • hemorrhage, or bleeding, in your brain
  • hydrocephalus, or fluid buildup in your skull
  • infections or swelling
  • injuries to your head, face, or skull
  • stroke
  • tumors

Your doctor may order a cranial CT scan if you’ve had an injury or display any of these symptoms with no apparent cause:

  • fainting
  • headache
  • seizures, especially if any occurred recently
  • 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 your 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.

Some people find the CT scanner stressful or claustrophobic. Your doctor may suggest a sedative to keep you calm during the procedure. A sedative will also help keep you still. If your child is having the CT scan, their doctor may recommend a sedative for these same reasons.

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 creates 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.

Contrast dye helps highlight some areas better on CT images. For example, it can highlight and emphasize blood vessels, intestines, and other areas. The dye is given through an intravenous line inserted into a vein of your arm or hand.

Often, images are first taken without contrast, and 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 aren’t recommended for pregnant women.

You’ll want to be aware of some extra precautions 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.

Side effects and risks for a cranial CT scan involve discomfort, exposure to radiation, and allergic reaction to the contrast dye.

Discuss any concerns with your doctor before the test so you can assess the potential risks and benefits for your medical condition.


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.

Radiation exposure

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 it 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 head MRI scan or ultrasound, which don’t use radiation.

Allergic reaction to contrast

Tell your doctor before the scan if you’ve ever had an allergic reaction to contrast dye.

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. after the test, you may need to drink extra fluids 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.

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.

A radiologist will interpret the results of the test 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. Depending on the results, your doctor might order more tests. Or if they’re able to reach a diagnosis, they will go over next steps with you, if any.