What is epilepsy and how can MRI help?

Specialties Article 4 Minute Read GE Healthcare Global

In support of raising awareness for epilepsy and specifically on March 26th, people around the world are encouraged to wear purple. Learning more about what epilepsy is and its prevalence could help bring further understanding to the importance of spreading awareness on this topic. So what is epilepsy? Epilepsy is the fourth most common neurological disorder.1 In fact, there are more than 2.26 million people in the United States that have epilepsy.2

Epilepsy is a disorder in the central nervous system (CNS) where brain activity abnormalities cause seizures.1-4 Seizures are periods of unusual behavior, sensations, and occasionally loss of awareness. Anyone can develop epilepsy and their symptoms can vary widely. Treatment or surgery may control seizures for most people with epilepsy, though some have epilepsy their whole life, while others don’t. Children with epilepsy may outgrow the disorder.

Types of seizures

Epileptic seizures can come in a variety of different forms. There are a few areas that it is important to consider when providing descriptions of seizures. These areas were put forward by the International League Against Epilepsy and include the onset or beginning of a seizure, the level of awareness of the patient during the seizure, and whether movement happens during a seizure.4 There are two main categories of seizures: focal onset and generalized onset.

Focal onset seizures appear to result from abnormal activity of one area of the brain.2,4 Focal seizures can be without loss of consciousness or with impaired awareness. The first type may alter emotions or senses, causing involuntary jerking of a body part, or appear with sensory symptoms, like tingling, dizziness, and flashing lights. The latter type causes a change in consciousness or awareness. The person having the seizure may stare into space, not respond to their environment or perform repetitive movements.

Generalized seizures can be categorized further into any of six subcategories.2 These subcategories are absence, tonic, atonic, clonic, myoclonic and tonic-clonic. Each of these seizures result from abnormalities that appear to involve all areas of the brain, instead of just one.

    • Absence seizures, a.k.a. petit mal seizures, typically occur in children. They are characterized by staring into space or subtle body movements, such as eye blinking or lip smacking. Absence seizures may occur in clusters and may cause a brief loss of awareness.2
    • Tonic seizures are characterized by a stiffening of muscles. The muscles which stiffen are typically those in the back, arms or legs. Because of this, patients having tonic seizures may end up falling to the ground.2
    • Atonic seizures, sometimes called drop seizures, typically are the opposite of tonic seizures. Instead of their muscles stiffening, patients may experience a loss of muscle control, which can cause a sudden collapse or fall.2
    • Clonic seizures involved the repeated or rhythmic jerking of muscles. This often affects the muscles in the neck, face and arms.2
    • Myoclonic seizures result in sudden brief jerks or twitches of the arms and legs.2
    • Tonic-clonic seizures, also known as grand mal seizures, are often the most dramatic. They can cause a loss of consciousness or body stiffening and shaking. Patients may also experience loss of bladder control or tongue biting, though not always.2

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What does MRI show?

Magnetic resonance imaging (MRI) can be a particularly useful tool for radiologists and physicians with epileptic patients. MRI uses a superconducting magnet and the magnetic field around a patient along with RF coils placed on or around the patient’s body area of interest to produce the images needed. The computer receives the signals emitted by the patient. MRI is non-invasive and typically causes no harm to the patient. The data that the computer collects is then taken and the computer software creates the images. These images are then analyzed by the radiologists and reported to the ordering physician for review.

MR can provide detailed images of the tissue structures of the body, which is particularly informative for imaging of the brain. In some cases, MRI techniques can be used to determine the composition of tissue and liquid, such as in tumors or lesions. Diffusion weighted imaging (DWI) is an MRI technique which is used to image diffusivity of water molecules (Brownian motion) and can increase sensitivity and specificity of lesions. Spectroscopy, another technique, may show the chemical shifts that result from the sequence.5 Spectroscopy may not be used routinely for imaging epilepsy patients, but may provide additional information on electroencephalographic abnormalities after the abnormalities are first noted on conventional MRI.5 Functional MRI (fMRI) shows the signals throughout the body while the patient is performing an action or while the brain’s synapses are firing. fMRI can be helpful when using MRI as a pre-surgical tool for some patients.6 These three methods can be particularly helpful for physicians with epilepsy patients, and each provides its own unique information on the patient and the changes occurring in the brain.5,6

MRI can provide a great deal of information, to show the anatomical changes associated with seizure activity, to inform a radiologist and physician with epileptic patient’s.6 There are however other tools that can also inform the radiologist and physician such as positron emission tomography (PET) and computed tomography (CT).

Vital information for the treatment of epilepsy can be provided by imaging techniques such as MRI, PET and CTto inform medicinal or surgical treatment. As epilepsy is the fourth most common neurological disorder and patients may have a number of different types of seizures, MRI may help to determine the origin or allow doctors to monitor lesions.

References

1. Joseph I. Sirven and Patricia O. Shafer. “What is Epilepsy?” Epilepsy.com. 21 January 2014. Web. 20 March 2019. <https://www.epilepsy.com/learn/about-epilepsy-basics/what-epilepsy>.

2. Mayo Clinic Staff. “Epilepsy.” MayoClinic.org. 16 March 2019. Web. 20 March 2019. <https://www.mayoclinic.org/diseases-conditions/epilepsy/symptoms-causes/syc-20350093>.

3. Liya Beyderman. “Seizures.” KidsHealth.org. October 2016. Web. 20 March 2019. <https://kidshealth.org/en/parents/seizure.html>.

4. Elaine Kiriakopoulos and Patricia O. Shafer. “Types of Seizures.” Epilepsy.com. March 2017. Web. 21 March 2019. <https://www.epilepsy.com/learn/types-seizures>.

5. Elliott Friedman. “Epilepsy Imaging in Adults: Getting It Right.” American Journal of Roentgenology. 2014; 203: 1093-1103. doi: 10.2214/AJR.13.12035

6. Fernando Cendes, et al. “Neuroimaging of epilepsy.” Handb Clin Neurol. 2016; 136: 985-1014. Web. 21 March 2019. doi: 10.1016/B978-0-444-53486-6.00051-X.