Cranial CT scan

Answer 1

Definition

A cranial computed tomography (CT) scan is an imaging method that uses x-rays to create cross-sectional pictures of the head, including the skull, brain, eye sockets, and sinuses.

See: Computed tomography

Alternative Names

Brain CT; Head CT; CT scan - skull; CT scan - head; CT scan - orbits; CT scan - sinuses

How the test is performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner. Depending on the study being done, you may need to lie on your stomach, back, or side.

A cranial CT scan produces images from your upper neck to the top of your head.

You must be still during the exam, because movement causes blurred images. If you can't stay still, pillows or cushions may be placed around your head to hold it in place.

Once inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam in one continuous motion.) You may be told to hold your breath for short periods of time.

Small detectors inside the scanner measure the amount of x-rays that make it through the part of the body being studied. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of your head can be created by stacking the individual slices together.

Special dye, called contrast, may be used to help highlight blood vessels and look for a mass (tumor). If this is needed, the health care provider will inject the dye into a vein.

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

How to prepare for the test

Usually, no preparation is needed. However, if contrast is needed, you may be asked not to eat or drink anything for 4-6 hours before the test.

Tell your health care provider if you are allergic to IV contrast.

Since x-rays have difficulty passing through metal, 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 give 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:

• Abnormal development of the head or neck
• Bleeding in the brain
• Brain infection
• Brain tumor

A cranial CT may also be done to:

• Determine the cause of a headache
• Determine the cause of vision problems, muscle weakness, numbness and tingling, hearing loss, speaking difficulties, or swallowing problems
• Diagnose a new stroke
• Evaluate changes in thinking or behavior
• Evaluate injury to the head and face

What abnormal results mean

Abnormal results may be due to:

• Abnormal blood vessels (arteriovenous malformation)
• Abnormal sinus drainage
• Aneurysm
• Bleeding (for example, chronic subdural hematomaor intracranial hemorrhage)
• Bone infection
• Brain abscessor infection
• Brain damage due to injury
• Brain tissue swelling or injury
• Brain tumor or mass
• Cerebral atrophy (loss of brain tissue)
• Hydrocephalus(fluid collecting in the skull)
• Problems with the hearing nerve
• Stroke or transient ischemic attack (TIA)

What the risks are

Iodine is the usual contrast dye. Some patients are allergic to iodine and may experience a reaction that may include hives, itching, nausea, breathing difficulty, or other symptoms.

As with any x-ray examination, radiation is potentially harmful. Consult your health care provider about the risks if multiple CT scans are needed over a period of time.

Special considerations

A CT scan can decrease or eliminate the need for invasive procedures to diagnose problems in the skull. This is one of the safest means of studying the head and neck.

Alternative tests that may be performed in place of Cranial CT scan include:

• MRI of the head
• Positron emission tomography (PET) scan of the head
• Skull x-ray

References

Shaw AS, Dixon AK. Multidetector computed tomography. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 4.

Saunders D, Jager HR, Murray AD, Stevens JM. Skull and brain: methods of examination and anatomy. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 55.

Answer 2

Definition

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

Alternative Names

Brain CT; Head CT; CT scan - skull; CT scan - head; CT scan - orbits; CT scan - sinuses; Computed tomography - cranial

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

What abnormal results mean

Abnormal results may be due to:

• Abnormal blood vessels (arteriovenous malformation)
• Aneurysm in the brain
• Bleeding (for example, chronic subdural hematomaor intracranial hemorrhage)
• Bone infection
• Brain abscessor infection
• Brain damage due to injury
• Brain tissue swelling or injury
• Brain tumor or other growth (mass)
• Cerebral atrophy (loss of brain tissue)
• Hydrocephalus (fluid collecting in the skull)
• Problems with the hearing nerve
• Stroke or transient ischemic attack (TIA)

What the risks are

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans do expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your doctor should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Some people have Allergies to contrast dye. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.

• The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting,sneezing, itching,or hives may occur.
• If you absolutely must be given such contrast, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

Special considerations

A CT scan can reduce or avoid the need for invasive procedures to diagnose problems in the skull. This is one of the safest ways to study the head and neck.

Other tests that may be done instead of Cranial CT scan include:

• MRI of the head
• Positron emission tomography (PET) scan of the head
• Skull x-ray

References

Shaw AS, Dixon AK. Multidetector computed tomography. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 4.

Saunders D, Jager HR, Murray AD, Stevens JM. Skull and brain: methods of examination and anatomy. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 55.

Reviewed By

Review Date: 11/22/2010

Ken Levin, MD, Private Practice specializing in Radiology and Nuclear Medicine, Allentown, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.