MRI of the head Health Article
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How the test will feel
There is no pain. The magnetic field and radio waves are not felt. Some people experience a claustrophobic feeling from being inside the scanner. The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises during normal operation. Ear plugs are usually given to the patient to reduce the noise. A technologist observes the patient during the entire procedure and may be spoken to through an intercom in the scanner. Some MRI scanners are equipped with televisions and special headphones to help the examination time pass. Excessive movement can blur MRI images and cause errors in the image. If the patient has difficulty lying still or is very anxious, they may be given medicine to relax them (a sedative), by mouth or through a vein. There is no recovery, unless sedation was necessary. After an MRI scan, you can resume normal diet, activity, and medications.
Why the test is performed
MRI provides detailed pictures of the brain and nerve tissues from multiple angles without obstruction by overlying bone. In fact, about 90% of all MRI scans are for brain or spine disorders. MRI is the procedure of choice for most brain disorders. MRI is particularly useful in brain and neurological disorders, because it can clearly show different types of nerve tissue. It provides clear pictures of the brainstem and posterior brain, which are difficult to view on CT scan. It is also useful for the diagnosis of demyelinating disorders. These are disorders such as multiple sclerosis, which cause destruction of the myelin covering of the nerve. MRI is a noninvasive procedure that can evaluate blood flow and the flow of cerebrospinal fluid (CSF). MRI can distinguish tumors or other lesions from normal tissues. MRI is sometimes used to avoid the dangers of angiography or of repeated exposure to radiation.
What abnormal results mean
The sensitivity of an MRI depends, in part, on the experience of the radiologist. An MRI of the head may reveal disorders including:
Additional conditions under which the test may be performed:
What the risks are
There is no ionizing radiation involved in MRI. To date, there have been no documented significant side effects of the magnetic fields and radio waves used on the human body during an MRI scan. The most common MR intravenous contrast agent, gadolinium, is very safe, and although there have been documented allergic reactions to it, it is an extremely rare occurrence. However, gadolinium should not be given if you are pregnant because of potential harm to the fetus. If sedation is used, there are associated risks of over-sedation. The technologist monitors the patient's vital signs, including heart rate and breathing as needed. People have been harmed in MRI machines when they did not remove metal objects from their clothes or when metal objects were left in the room by others.
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Reviewer Info: Stuart Bentley-Hibbert, M.D., Ph.D., Department of Radiology, Weill Cornell Medical Center, New York, NY. Review provided by VeriMed Healthcare Network.; ADAM Health Illustrated Encyclopedia, 10/25/2006 |
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