Dense-Array Electroencephalography with Source Imaging Gives a New View into Epilepsy

Dense-Array Electroencephalography with Source Imaging Gives a New View into Epilepsy

Temporal lobe seizures have a significant chance to induce impairment of normal brain functions. Even after the termination of ictal discharges, during the post-ictal period, loss of consciousness, decreased responsiveness or other cognitive dysfunctions can persist. Previous studies have found various anatomical and functional abnormalities accompanying temporal lobe seizures, including an abnormal elevation of cortical slow waves. Intracranial electroencephalography studies have shown a prominent increase of lower frequency components during and following seizures that impair (complex partial seizures) but not those that preserve (simple partial seizures) normal consciousness and responsiveness. However, due to the limited spatial coverage of intracranial electroencephalography, the investigation of cortical slow waves cannot be easily extended to the whole brain. In this study, we used scalp electroencephalography to study the spectral features and spatial distribution of post-ictal slow waves with comprehensive spatial coverage. We studied simple partial, complex partial and secondarily generalized seizures in 28 patients with temporal lobe seizures. We used dense-array electroencephalography and source imaging to reconstruct the post-ictal slow-wave distribution. In the studied cohort, we found that a ‘global’ spectral power shift to lower frequencies accompanied the increased severity of seizures. The delta spectral power relative to higher frequency bands was highest for secondarily generalized seizures, followed by complex partial seizures and lastly simple partial seizures. In addition to this ‘global’ spectral shift, we found a ‘regional’ spatial shift in slow-wave activity. Secondarily generalized seizures and complex partial seizures exhibited increased slow waves distributed to frontal areas with spread to contralateral temporal and parietal regions than in simple partial seizures. These results revealed that a widespread cortical network including temporal and fronto-parietal cortex is involved in abnormal slow-wave activity following temporal lobe seizures. The differential spectral and spatial shifts of post-ictal electroencephalography activity in simple partial, complex partial and secondarily generalized seizures suggest a possible connection between cortical slow waves and behavioural and cognitive changes in a human epilepsy model.

The study’s findings include:

Important data about brain function can be gathered through non-invasive methods, not only during a seizure, but immediately after a seizure.

The frontal lobe of the brain is most involved in severe seizures.

Seizures in the temporal lobe are most common among adults. The new technique used in the study will help determine the side of the brain where the seizures originate.

“This is the first-ever study where new non-invasive methods were used to study patients after a seizure instead of during a seizure,” said Bin He, a biomedical engineering professor in the University of Minnesota’s College of Science and Engineering and senior author of the study. “It’s really a paradigm shift for research in epilepsy.”

Epilepsy affects nearly 3 million Americans and 50 million people worldwide. While medications and other treatments help many people of all ages who live with epilepsy, about 1 million people in the U.S. and 17 million people worldwide continue to have seizures that can severely limit their lives.

The biggest challenge for medical researchers is to locate the part of the brain responsible for the seizures to determine possible treatments. In the past, most research has focused on studying patients while they were having a seizure, or what is technically known as the “ictal” phase of a seizure. Some of these studies involved invasive methods such as surgery to collect data.

In the new study, researchers from the University of Minnesota and Mayo Clinic used a novel approach by studying the brains of 28 patients immediately after seizures, or what is technically know as the “postictal” phase of a seizure. They used a specialized type of non-invasive EEG with 76 electrodes attached to the scalp for gathering data in contrast to most previous research that used 32 electrodes. The researchers used specialized imaging technology to gather data about the patient. The findings may lead to innovative means of locating the brain regions responsible for seizures in individual patients using non-invasive strategies.

“The imaging technology that we developed here at the University of Minnesota allowed us to tackle this research and gather several thousand data points that helped us determine our findings,” He said. “The technical innovation was a big part of what helped us make this discovery.”

He, who was recently appointed the director of the University of Minnesota’s Institute for Engineering in Medicine, said this study was also a good example of a true partnership between engineering and medicine to further medical research.

“The innovations in engineering combined with collaborations with clinicians at Mayo Clinic made this research a reality,” He said.

In addition to He, members of the research team included University of Minnesota biomedical engineering Ph.D. student Lin Yang; Gregory A. Worrell, Mayo Clinic, Neurology and Division of Epilepsy; Cindy Nelson, Mayo Clinic, Neurology; and Benjamin Brinkmann, Mayo Clinic, Neurology. The research was funded by the National Institutes of Health.

Epileptic seizures have mystified people for thousands of years, appearing in the Bible numerous times as evidence of wicked spirits invading innocent human hosts. Though Jesus reportedly treated these cases with divine intervention, he failed to leave clinical guidelines, leaving modern clinicians to continue to be confounded by epilepsy.

An important factor when deciding what treatment option to offer an individual patient is knowing where in the brain the electrical storm is generated. Commonly EEG is used when a patient is experiencing a seizure to do this localization, but now researchers from University of Minnesota and Mayo Clinic have shown that a high density EEG test immediately following a seizure offers similar ability. They used an EEG array of 76 electrodes (more than double the 32 usually used) to study 28 epileptic patients and discovered that the frontal lobe is a predominant source of the seizure during particularly severe episodes. The researchers hope the new technology will be adopted to help individual patients address the unique nature of their disease.

Source : http://brain.oxfordjournals.org/content/early/2012/08/24/brain.aws221.abstract

Related Posts Plugin for WordPress, Blogger...
Be Sociable, Share!

About the Author

has written 1822 posts on this blog.

Copyright © 2017 Medical Technology & Gadgets Blog MedicalBuy.net. All rights reserved.
Proudly powered by WordPress. Developed by Deluxe Themes