Credit: Thinkstock When our doctors order tests because of our Migraines or headaches, we often have questions about those tests. We want to know what the tests can reveal, and we want to know how they’re performed.
Although there are no diagnostic tests to confirm a diagnosis of Migraine, there are times when our doctors may order tests to rule out other possible causes our symptoms before attributing them to our Migraines. This may be done at the time of diagnosis or later on if our Migraines change patterns or new symptoms occur.
One of these tests is a CT scan. CT stands for computerized tomography and is an imaging study that uses x-rays to create pictures of cross-sections of the body. In the case of Migraines, the CT scans are most likely to be of the head and neck.
How a CT Scan Is Performed:
- The patient is asked to lie on a narrow table that slides into the center of the CT scanner.
- Once the patient is inside the scanner, the machine’s x-ray beam rotates around them. 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 body area can be created by stacking the slices together.
- The patient must lie still during the exam because movement can cause blurred images. The patient may be told to hold their breath for short periods of time.
- Complete scans usually take only a few minutes. The newest scanners can image the entire body in less than 30 seconds.
Preparing for a CT Scan:
- Leave jewelry at home since you’ll need to remove it before the scan.
- Sometimes, a CT scan may require a special contrast dye to be delivered to help certain areas show up better on the x-rays.
- Be sure to tell your doctor know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to avoid another reaction.
- Contrast can be given several ways, and depends on the type of CT being performed:
- Through a vein (IV) in the hand or forearm.
- Orally. The contrast liquid may taste chalky, although some are flavored. The contrast passes out of your body through the stools.
- If contrast is used, you may also be asked not to eat or drink anything for four to six hours before the test.
- If you’re to receive contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage). People taking this medicine may need to stop temporarily.
How a CT Scan Feels:
- Lying on the hard table can cause some people to experience discomfort.
- If administered IV, contrast may cause a bit of a burning feeling; a metallic taste in the mouth; and a warm, flushing feeling throughout the body. These feelings are normal, and they usually stop within a few seconds.
Risks Associated with a CT Scan:
- The main risks of a CT scan include:
- Allergic reaction to contrast dye
- Being exposed to radiation
- CT scans present a higher exposure to radiation than regular x-rays. Many x-rays or CT scans over time may increase the risk of cancer, but the risk from any one scan is small.
- The most common type of IV contrast contains iodine. If the patient is allergic to iodine, contrast may cause itching, hives, sneezing, and / or nausea or vomiting.
- If you absolutely must be given such contrast, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.
- Since the kidneys help remove iodine from the body, extra fluids may be recommended to help flush it out, especially if the patient has diabetes or kidney disease.
- In rare cases, contrast may cause life-threatening anaphylaxis. If you have any trouble breathing during the test, tell the scanner operator immediately. CT scanners have an intercom and speakers, so the operator can hear the patient at all times.
Summary and Comments:
If your doctor orders a CT scan, don’t hesitate to ask any questions you may have about how it will be done, if you’ll need to have contrast, and the risks associated with CT scans. One question you should ask is why your doctor is ordering a CT scan rather than an MRI. The American Headache Society’s Choosing Wisely Task Force released, "Five Things Physicians and Patients Should Question. One of them is:
"Don’t perform computed tomography (CT) imaging for headache when magnetic resonance imaging (MRI) is available, except in emergency settings. When neuroimaging for headache is indicated, MRI is preferred over CT, except in emergency settings when hemorrhage, acute stroke or head trauma are suspected. MRI is more sensitive than CT for the detection of neoplasm, vascular disease, posterior fossa and cervicomedullary lesions and high and low intracranial pressure disorders. CT of the head is associated with substantial radiation exposure which may elevate the risk of later cancers, while there are no known biologic risks from MRI."
1 Adam. “CT Scan” Medline. November 9, 2012.
2 The American Headache Society’s Choosing Wisely ® Task Force. “Five Things Physicians and Patients Should Question.” The American Headache Society. November, 2013.
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© Teri Robert, 2014 Last updated March 10, 2014.