What is neuroimaging?

Sometimes epilepsy is caused by abnormalities in the structure of the brain. These can be such things as too much spinal fluid (hydrocephalus), scar tissue, or a tangle of blood vessels (vascular malformation). Tests that can take pictures of the brain, called "neuroimaging," can tell doctors whether you have one of these conditions. These tests are performed to look for the cause of your seizures (which can be identified for about half of patients) or to make sure that you don't have some other medical condition.

The most common neuroimaging tests for epilepsy are computed tomography (CT or CAT scan) and magnetic resonance imaging (MRI). Both produce a picture of how the brain looks. MRI is preferred because it provides more information than CT. In fact, MRI is recommended as the imaging test of choice.

What neuroimaging studies do I need?

For some types of epilepsy, a neuroimaging study may not be necessary. For most people with newly diagnosed epilepsy, however, neuroimaging is important for the diagnosis.

Neuroimaging should always be considered if the cause of your seizures is something that is apt to change, such as a benign tumor, which may grow, or a vascular malformation, which could bleed. In these situations, your doctor may want you to have follow-up scans to keep an eye on the situation. MRI also can be helpful if the cause of your seizures is suspected but indefinite, such as a mild head injury.

Many doctors will not order a CT or MRI scan for patients with certain well-defined epilepsy syndromes that are often genetic, such as absence seizures, juvenile myoclonic epilepsy, or benign rolandic epilepsy, because the results are almost always normal or unrelated to epilepsy.

What are less common forms of neuroimaging?

CT and MRI show the brain’s structure, or how it looks. Other neuroimaging methods show its function, or how it works. They are generally used to evaluate patients before epilepsy surgery or as research tools. These methods include:

• Single-photon emission computed tomography (SPECT), which shows a map of blood flow through different parts of the brain.
• Positron emission tomography (PET), which shows how much sugar (glucose) or oxygen is metabolized (used up) by various areas of the brain.
• Magnetoencephalography (MEG), which measures tiny magnetic fields to study the brain's electrical patterns with less interference from the skull and other tissues than on an EEG.
• Magnetic resonance spectroscopy (MRS), which examines signals generated by elements such as phosphorus. MRS uses technology similar to that of MRI, which studies hydrogen atoms. MRS data can be used, for example, to learn about metabolism in the brain.
• Ultrasound, which can look at fluid or blood in the brain of a newborn baby

Topic Editor:Ruben Kuzniecky, M.D.
Last Reviewed:4/16/04