Brain Imaging for Epilepsy
What Is Neuroimaging?
Neuroimaging takes pictures of the brain to look for the cause of your seizures (which can be identified for about half of patients) or ensure you don't have some other medical condition. These tests can help when epilepsy is caused by changes in the structure of the brain, such as too much spinal fluid (hydrocephalus), scar tissue, or a tangle of blood vessels (vascular malformation).
The most common imaging tests for epilepsy are computed tomography (CT 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.
Do I Need Brain Imaging for Seizures?
For some types of epilepsy, an imaging may not be necessary. For most people with newly diagnosed epilepsy, however, brain imaging is important to make the correct for 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 recommend follow-up scans to keep an eye on the situation. MRI also can be helpful if the cause of your seizures is suspected not clear, 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.
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Different Epilepsy SyndromesTypes of Brain Imaging
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 brain imaging methods include:
MEG
Magnetoencephalography (MEG): Measures tiny magnetic fields to study the brain's electrical patterns with less interference from the skull and other tissues than on an EEG.
Computer Tomography
Computed tomography (CT or CAT scan) was introduced in the United States in the early 1970s. It revolutionized the practice of neurology and neurosurgery by letting doctors see inside the brain without surgery for the first time. The CT scan is normal in most people with epilepsy. Still, abnormalities that might be seen include atrophy (shrinking of the brain), scar tissue, strokes, tumors, or abnormal blood vessels.
Like ordinary x-rays, CT scans expose the patient to radiation. However, the amount is low, and the procedure is safe even if repeated several times. The scanner is a large machine, but less confining for patients than an MRI machine.
The advantages of CT scanning include speed and easy availability in most places. It has lower resolution for showing brain structures than MRIs, however, and i is less effective at discriminating between the brain's gray matter and white matter.
PET Scan
A PET (positron emission tomography) scan shows the brain uses of oxygen or sugar (glucose). Similarly to a SPECT, a very low, safe dose of a radioactive substance is injected into your arm and the scanner records how it travels through the brain. Not all types of PET scans look alike, but often different colors are used to show areas of higher or lower use of oxygen or sugar.
- This test can help to identify the area of the brain where partial seizures arise.
- It may be done in the period between seizures (the interictal period).
- PET scans are expensive, and very few patients with epilepsy need them. Most insurance companies will pay for PET scans for patients who are being evaluated for epilepsy surgery.
SPECT
Single-photon emission computed tomography (SPECT) is a nuclear radiology study that measures the blood flow in the brain.
- A safe, short-lived radioactive substance is injected into the arm and a CT (computed tomography) scan is performed shortly afterwards.
- The more blood flowing through an area in the brain, the brighter that area lights up on the scan.
- During a seizure, more blood flows to the area where the seizure comes from, making this test valuable in finding the seizure onset zone.
Image: Examples of subtraction ictal SPECT co-registered to MRI (SISCOM)
Finding Where Seizures Start
A special protocol has been developed to obtain more specific information about where seizures start in the brain. The test compares blood flow during and in between seizures and then superimposes those images on an MRI (magnetic resonance imaging). This protocol is called subtraction ictal SPECT co-registered to MRI, or SISCOM.
- This study is performed during an admission to the Epilepsy Monitoring Unit, as the injection needs to be performed during a seizure by specially certified staff.
- A second injection is performed at least 24 hours later, in between seizures, to look at blood flow between seizures.
SISCOM studies are performed only in certain epilepsy centers and onl during an admission in the Epilepsy Monitoring Unit. The information obtained needs to be considered along with the EEG data and MRI to determine the seizure onset zone.
MRS
Magnetic resonance spectroscopy (MRS): 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
Ultrasound: Can look at fluid or blood in the brain of a newborn baby
Learn More:
Epilepsy SurgeryResources
Epilepsy Centers
Epilepsy centers provide you with a team of specialists to help you diagnose your epilepsy and explore treatment options.
Epilepsy Medication
Find in-depth information on anti-seizure medications so you know what to ask your doctor.
Epilepsy and Seizures Helpline
Call our Epilepsy and Seizures Helpline and talk with an epilepsy information specialist or submit a question online.
Tools & Resources
Get information, tips, and more to help you manage your epilepsy.
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