Nav: Home

Epilepsy: Seizures not forecastable as expected

September 25, 2019

Epileptic seizures can probably not be predicted by changes in brain wave patterns that were previously assumed to be characteristic precursors. This is the conclusion reached by scientists from the University of Bonn in a recent study. The results are now published in the journal "Chaos: An Interdisciplinary Journal of Nonlinear Science".

During an epileptic seizure, large nerve cell clusters in the brain discharge simultaneously. The consequences are dramatic muscle spasms and loss of consciousness, which can be life-threatening. Many researchers assume that the brain has crossed a so-called "tipping point", which almost inevitably leads to a seizure.

The lead-up to this tipping point is supposedly heralded by characteristic changes in brain waves - so says a common hypothesis. According to this theory, nerve cell networks reproduce their own activity when close to this point: The brain waves they produce are very similar to previous ones. At the same time, they react to disturbances with much stronger discharges than normal. Additionally, it takes longer for their activity to normalize. "We call this 'critical slowing down', CSL for short," explains Prof. Dr. Klaus Lehnertz from the Department of Epileptology at the University Hospital Bonn.

Together with his former colleague Theresa Wilkat and his doctoral student Thorsten Rings, the physicist searched for such CSL events. For this purpose, the researchers analyzed brain wave recordings of 28 subjects with epilepsies that could not be treated with medication. Measurements were taken using electrodes implanted at various sites in the subjects' brains. "This is for diagnostic purposes, for example, to identify the site from which the seizures originate," explains Lehnertz.

Unsuitable as an early warning system

The subjects had up to 70 sensors each in their brains. The scientists analyzed each individual EEG curve recorded by the sensors using sophisticated statistical methods. "We not only considered the hours before an attack, but also looked at a period of up to two weeks," Wilkat explains.

The result was disappointing: "Although we found a number of CSL events, these usually occurred completely independent of a seizure," emphasizes Lehnertz. "Only in two subjects we were able to observe a weak relationship with subsequent seizures." His conclusion: "Critical slowing down" is not suitable as an early warning sign, even if this is claimed in literature again and again.

He considers it more promising not to look at individual sites in the brain, but to understand these as parts of a network that influence each other. The cause of a seizure is most likely not the activity of a single nerve cell cluster that gets out of control. "Instead, there are feedback and amplification effects that, as a whole, lead to this massive temporary brain malfunction," he emphasizes. Understanding these processes will also allow better forecasting techniques to be developed.

Epileptic seizures usually strike like a bolt from the blue, which significantly impacts the daily lives of those affected. For example, sufferers are not allowed to drive a car or carry out certain activities with a high risk of injury. Epileptologists, physicists and mathematicians have therefore been trying to predict the dangerous malfunctions of the brain for more than three decades - so far with mixed success: There certainly are systems that can detect seizure precursors (using indicators other than "critical slowing down"), but at present they work only for about half of the subjects and are not particularly reliable. They can not recognize every precursor of a seizure and are also prone to false alarms.

However, this is not the only reason why scientists around the globe are looking for more reliable indicators in order to be able to warn subjects in good time. They also hope to be able to prevent an attack in advance through appropriate interventions.
-end-
Publication: Theresa Wilkat, Thorsten Rings and Klaus Lehnertz: No evidence for critical slowing down prior to human epileptic seizures; Chaos: An Interdisciplinary Journal of Nonlinear Science, DOI: 10.1063/1.5122759

Contact:

Prof. Dr. Klaus Lehnertz
Department of Epileptology
University Hospital Bonn
Tel. +49 (0228) 287-15864
E-mail: Klaus.Lehnertz@ukbonn.de

University of Bonn

Related Brain Articles:

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.
Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.
Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.
Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.
BRAIN Initiative tool may transform how scientists study brain structure and function
Researchers have developed a high-tech support system that can keep a large mammalian brain from rapidly decomposing in the hours after death, enabling study of certain molecular and cellular functions.
Wiring diagram of the brain provides a clearer picture of brain scan data
In a study published today in the journal BRAIN, neuroscientists led by Michael D.
Blue Brain Project releases first-ever digital 3D brain cell atlas
The Blue Brain Cell Atlas is like ''going from hand-drawn maps to Google Earth'' -- providing previously unavailable information on major cell types, numbers and positions in all 737 brain regions.
Landmark study reveals no benefit to costly and risky brain cooling after brain injury
A landmark study, led by Monash University researchers, has definitively found that the practice of cooling the body and brain in patients who have recently received a severe traumatic brain injury, has no impact on the patient's long-term outcome.
Brain cells called astrocytes have unexpected role in brain 'plasticity'
Researchers from the Salk Institute have shown that astrocytes -- long-overlooked supportive cells in the brain -- help to enable the brain's plasticity, a new role for astrocytes that was not previously known.
Largest brain study of 62,454 scans identifies drivers of brain aging
In the largest known brain imaging study, scientists from Amen Clinics (Costa Mesa, CA), Google, John's Hopkins University, University of California, Los Angeles and the University of California, San Francisco evaluated 62,454 brain SPECT (single photon emission computed tomography) scans of more than 30,000 individuals from 9 months old to 105 years of age to investigate factors that accelerate brain aging.
More Brain News and Brain Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab