Researchers Identify Seizure-associated Depolarization As Cause Of Post-ictal Symptoms

People pinch temporal lobe epilepsy successful peculiar often rotation astir aimlessly and unconsciously aft a seizure. Researchers astatine nan University Hospital Bonn (UKB), nan University of Bonn, and nan German Center for Neurodegenerative Diseases (DZNE) person identified a neurobiological system that could beryllium responsible for this alleged post-ictal wandering and perchance different postictal symptoms. According to their hypothesis, epileptic seizures are not straight responsible for post-ictal symptoms, but alternatively seizure-associated depolarization waves, besides known arsenic spreading depolarization (SD). The results of nan studies person now been published successful nan diary Science Translational Medicine.

In mundane objective practice, symptoms are regularly observed aft epileptic seizures, known arsenic "post-ictal symptoms", which, successful opposition to nan usually short long of seizures, typically past respective minutes to hours. Besides symptoms specified arsenic impaired reside and connection comprehension, a authorities of disorientation whitethorn occur. This wandering about, known successful method position arsenic postictal wandering, tin sometimes beryllium life-threatening if, for example, nan affected unconscious personification runs onto nan street. "Postictal symptoms are traditionally referred to nan preceding epileptic seizure. However, it is unclear whether location is really a nonstop neurobiological relationship aliases whether nan symptoms are based connected different pathology," says corresponding writer Prof. Michael Wenzel from nan Dept. of Epileptology astatine nan UKB, who is besides a personnel of nan Transdisciplinary Research Area (TRA) "Life & Health" astatine nan University of Bonn.

Brain waves paralyze neural network

The Bonn investigation squad initially wanted to amended understand nan improvement of epilepsy arsenic a consequence of an first acute disease-in this case, viral encephalitis, an inflammation of nan encephalon caused by viruses. To do this, they utilized modern cellular-resolution fluorescence microscopy successful operation pinch electrophysiology and optogenetics successful a rodent model, which allows them to study web dynamics and nan connection of different encephalon compartment types successful nan surviving encephalon pinch precocious solution complete a play of months. "In doing so, we accidentally discovered a web arena successful nan hippocampus-a building applicable to epilepsy located wrong nan temporal lobe-that could explicate postictal symptoms but, surprisingly, does not correspond seizures themselves," says first writer Bence Mitlasóczki, a doctoral student astatine nan University of Bonn successful Prof. Wenzel's investigation group astatine nan UKB.

The observed arena consists of slow depolarization waves, which are chiefly known from neurological disorders specified arsenic migraine aliases acute encephalon injuries. This alleged spreading depolarization (SD) causes nan illness of nan neuronal membrane imaginable and nan nonaccomplishment of nan affected web for minutes to hours. The structures successful nan soul region of nan temporal lobe, specified arsenic nan hippocampus, whitethorn beryllium much delicate to SD during epileptic seizures than nan multisensory and centrifugal portion of nan cerebral cortex, known arsenic nan neocortex.

This could besides explicate why postictal symptoms are astir commonly observed successful temporal lobe epilepsy."

Bence Mitlasóczki, Doctoral Student, University of Bonn

In addition, SD waves are filtered retired successful modular objective EEGs successful epileptology because they are truthful slow. "As a result, SDs person been 'invisible' successful objective EEGs for decades, which is an important logic why nan strictly seizure-related conception of postictal symptoms persists, moreover though this whitethorn not beryllium accurate," states Prof. Wenzel.

Seizure-associated SD successful extent electrode recordings from group pinch epilepsy

In addition, nan Bonn researchers recovered grounds that seizure-associated SDs besides beryllium successful heavy regions of nan quality brain. To do this, they utilized a typical characteristic of pre-surgical diagnostics astatine nan UKB for group pinch difficult-to-treat epilepsy, which tests whether a section seizure attraction tin beryllium surgically removed. As portion of nan study, nan investigation squad initially examined immoderate participants utilizing nan electrodes implanted for test pinch further microwire bundles – which were established by nan moving group led by co-author Prof. Florian Mormann astatine nan UKB – to find whether section SD tin besides beryllium detected heavy successful nan quality encephalon arsenic soon arsenic nan EEG bandwidth is extended beyond nan world standard, frankincense enabling very slow imaginable fluctuations to beryllium recorded.

The conclusion of nan Bonn researchers is that epileptic seizures, though assumed to beryllium nan origin for decades, whitethorn not beryllium nan nonstop origin of postictal symptoms. "Our presumption is that section seizure-associated SD is simply a cardinal facet successful epilepsy that has been massively understudied to date," says co-author Prof. Heinz Beck from nan UKB and DZNE. He is simply a spokesperson for nan Transdisciplinary Research Area (TRA) "Life & Health" and a personnel of nan ImmunoSensation Cluster of Excellence astatine nan University of Bonn. The results constituent to a imaginable wide domiciled of SD successful a assortment of different postictal disorders, which now request to beryllium investigated further. "In addition, our results require a reappraisal of erstwhile studies which, because SD was filtered out, related effects and effect sizes to epileptic seizures, moreover though this whitethorn not beryllium nan case," says Prof. Wenzel. "Finally, our study could stimulate a chat connected whether nan world EEG modular needs to beryllium expanded to make SD straight visible successful objective EEG arsenic well."