Magnetic Resonance Imaging (MRI) Scan
MRI scans have become a crucial component in the evaluation of patient’s with epilepsy and particularly helpful in the evaluation for possible epilepsy surgery. The MRI shows the gross appearance of the brain and therefore, can give anatomic and pathological information of the brain. The use of the MRI scan in patients with epilepsy has been aided by FLAIR techniques and High Resolution MRI imaging and MRI volumetrics.
Fluid-attenuated Inversion Recovery (FLAIR) Imaging
Fluid-attenuated inversion recovery (FLAIR) improves the contrast and appearance of epilepsy-related abnormalities within the brain. It is often helpful to make clear contrast between abnormal findings (lesions) and normal findings (Cerebrospinal fluid).
High Resolution MRI
Obtaining small thin slices through the brain allows the images to be reconstructed to render a 3-D image of the brain. This technique is useful in identifying subtle lesions in the brain (i.e. cortical dysplasia) as well as their full extent of involvement.
After obtaining the high resolution MRI scan, computer software can be employed to calculate the respective volume of a brain structure on one side of the brain and compare it to the size of the same structure on the other side of the brain.
MRI volumetrics is occasionally used to evaluate the medial temporal structures which are frequently abnormal in a disease called ‘mesial temporal sclerosis’; a frequent cause of medically intractable epilepsy.
Positron Emission Tomography (PET scan)
Positron Emission Tomography (PET scan) is a neuro-imaging test of how the brain functions.
- PET scan is frequently used during evaluation for epilepsy surgery.
- FDG (fluoro-deoxy-glucose) PET is the most frequently used PET scan in epilepsy patients and provides information on how various regions of the brain utilize (metabolize) glucose (sugar).
Areas of the brain that do not metabolize glucose may reflect the dysfunctional region of the brain giving rise to seizures. This test often is helpful in providing additional information for accurately locating epilepsy in a specific region of the brain.
Ictal Single Photon Emission Computed Tomography (SPECT) Scan
Single Photon Emission Computed Tomography (SPECT scan) is another functional neuro-imaging test that helps in the localization of epilepsy to one region of the brain.
SPECT scan measures the relative blood flow in various regions of the brain at a specific moment in time. The test reflects a point in time at which a particular pharmacologic tracer is injected. When the tracer is injected soon after the onset of a seizure, information of blood flow during a seizure can be obtained. Areas that "light up" during this test may reflect the areas of the brain in which the seizure begins.
Magnetic Resonance Spectroscopy (MRS)
Magnetic resonance spectroscopy uses techniques from MRI imaging to give quantitative chemical information of the brain.
The information is usually displayed graphically. Various amounts of specific chemicals are evaluated to look for too much or too little of specific chemicals in specific regions of the brain. This information looks for an abnormal chemical signature in one region of the brain which can be useful in the evaluation for possible epilepsy surgery.