Category Archives: Current Research Advances

Especially Valuable Epilepsy Cure Advice

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Introduction 

Despite an extensive research effort and a wealth of available antiseizure medications, a cure for epilepsy remains elusive.  Riley and Danzer (2024) in a recent review discuss the reasons for this.  The path to a cure begins with preclinical research that focuses on the disease initiation termed epileptogenesis and its associated co-morbidities.  Epileptogenesis and disease-dependent co-morbidities, e.g. cognitive decline are key therapeutic targets for a cure.  Riley and Danzer (2024) provide especially valuable epilepsy cure advice by their critique of current preclinical models and proposed improvements.  The especially valuable epilepsy cure advice provided by these scientists is summarized below in a series of insights.

Preclinical animal model types:  acute, acquired and genetic

Especially valuable epilepsy cure advice – Insight 1 

In the development of antiseizure medications (Assessment 6 – Epilepsy Medication – Need to Know Information), the model of choice is the acutely provoked seizure model.  It is known that “acutely evoked seizures generated by normal brains, however, are mechanistically different from spontaneous seizures generated by epileptic brains” (Riley and Danzer, 2024).  Despite this, there are over 25 approved antiseizure medications. Many more are presently in clinical trials (Novel Anti-seizure Drugs – Ongoing Research). 

It is clear that antiseizure medications do not provide a cure for epilepsy.  Seizures return with drug cessation. As supported by clinical trial results, antiseizure medications have no ameliorating effects on epileptogenesis (origin of the seizure) or associated disease comorbidities e.g. cognitive decline.  Epilepsy cure advice proposes that basic preclinical research investigate ways to slow disease progression and initiate beneficial changes even when therapy is withdrawn (Riley and Danzer, 2024).  Since development of antiseizure medications will not yield a cure, a change in research focus is needed.

Especially valuable epilepsy cure advice – Insight 2 

Some of the preclinical epilepsy models are acquired epilepsy models induced by any number of traumatic brain injuries that go on to change the normal brain to an epileptic one.   These model will play an important role in finding a cure for epilepsy. 

However, in these models, it is important to distinguish between the effect of therapy on injury reduction per se and its effect on prevention of induced epileptogenesis.  Thus, determination of timing between these events is key.  Not surprisingly, early therapeutic interventions are more successful. This is because they reduce the effect of injury per se. Such therapy is obviously impractical in real life where brain injury is unpredictable.  Although the goal is epileptogenic therapy and disease modification, injury reduction in traumatic brain injury, where known, is still very important.

Especially valuable epilepsy cure advice – Insight 3 

Epilepsy is chronic.  Patients endure this disease for years.  Therefore, animal models need to be long term.   However, animal models are rarely chronic due to expense and time/labor commitment.  Yet chronic models would be the best ones to study.  Additional advantages of chronic models are many. They include the ability to obtain a baseline EEG, group animals according to similar seizure types, reduce variability and actually use fewer animals (Riley and Danzer, 2024).  Biomarkers would greatly facilitate investigations in epileptogenesis with chronic models (Engel and Pitkänen, 2020).  Sadly, there markers are still in early stages of development.

Especially valuable epilepsy cure advice – Insight 4 

Genetic models target a subset of epilepsies.  In these models, the time of expression of  abnormal gene(s) needs accurate determination to be relevant to epileptogenesis.  Additionally, long term studies with genetic models would be of considerable value.

Especially valuable epilepsy cure advice – Insight 5 

The epilepsy therapy screening program (ETSP)originated over 40 years ago. It provided essential data for many of the antiseizure medications approved by the FDA.  Historically, the ETSP has focused on identification of antiseizure medications for patients who are drug resistant. Currently, “the ETSP contract site has, for the first time, adopted a strategy to explore the potential of novel compounds to prevent epilepsy or to be disease modifying” (Wilcox et al., 2020).  The Neurological Diseases and Stroke of the National Institute of Health at the University of Utah funds and administers this program.  

Scientists now use several epilepsy models. These are an infection-induced model of temporal lobe epilepsy, genetic models and the validated KA-SE (Kainic Acid-Status Epilepticus) model. The latter produces spontaneous seizures.  The KA-SE model mimics temporal lobe epilepsy in humans both in epileptogenesis and disease progression. 

Analysis of therapies in these models has potential to achieve a cure. However, evaluation of therapies in novel etiologically relevant  models face many challenges.  These include lack of a positive control, need to develop an appropriate study design, determination of time window to treat following the brain insult, the duration of treatment and dose, and how long post treatment to observe animals.  These all remain for future evaluation but are realistically achievable.

Conclusions 

A number of researchers, notably those mentioned above and others, are providing especially valuable epilepsy cure advice.  It is important to move away from discovery of antiseizure medications that only suppress symptoms of epilepsy. These medications do nothing to prevent epileptogenesis or modify disease progression. They have failed to identify a cure for epilepsy.  Therapy testing in relevant animal models in essential to meet this goal.

References https://pubmed.ncbi.nlm.nih.gov/

1.  Riley VA, Danzer SC. Preclinical Testing Strategies for Epilepsy Therapy Development.Epilepsy Curr. 2024 Oct 25;25(1):51-57. doi: 10.1177/15357597241292197

2.  Engel J, Jr, Pitkänen A. Biomarkers for epileptogenesis and its treatment. Neuropharmacology. 2020;167:107735 doi: 10.1016/j.neuropharm.2019.107735

3.  Wilcox KS, West PJ, Metcalf CS. The current approach of the Epilepsy Therapy Screening Program contract site for identifying improved therapies for the treatment of pharmacoresistant seizures in epilepsy. Neuropharmacology. 2020;166:107811 doi: 10.1016/j.neuropharm.2019.107811

Novel Anti-seizure Drugs – Ongoing Research

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Introduction 

There is a urgent need for novel anti-seizure drugs that are both efficacious, safe and absent undesirable side effects.  In particular, the number of epilepsy patients who are drug resistant remains at an unacceptably high rate of 30%.  Untreated epilepsy has dire consequences including injury and death.  Additionally, those who are seizure free with drug therapy are not free from unwanted neurological side effects such as headaches, somnolence, and memory impairment.  Therefore, research for novel anti-seizure drugs that prevent seizures at doses absent of side effects is desperately needed but incredibly challenging (see Blog 15 for overview).  This blog discusses some of the novel anti-seizure drugs – ongoing research.

Specifically, this blog reviews three of 5 novel anti-seizure drugs that have met their goals in early clinical trials with positive data on anti-seizure efficacy (1).  Novel anti-seizure drugs introduced here are A) azetukalner (XEN1101),  B) bexicaserin (LP352), and C)  soticletstat (TAK-935). 

A) Azetukalner – Novel Anti-Seizure Drug Candidate

Azetukalner is a potassium channel opener that selectively acts on specific channels designated Kv7.2/7.3.  Importantly, azetukalner, by opening potassium channels, accelerates the movement of potassium ions through Kv7.2/7.3 channels across the nerve membrane.  This is an critical action because it lowers the membrane potential and essentially dampens excitable (seizure) nerve activity that promotes a seizure.  Thus, the rational is that the selectivity of azetukalner allows it to bypass all the other ion channels, potassium or otherwise, and focus only on excitable nerves where Kv7.2/7.3 channels need assistance.

Selectivity

Based on in vitro findings, azetukalner is 4 fold more selective for potassium Kv7.2/7.3 channels compared to closely related potassium (Kv) channels.  Additionally, oral dosing in classic seizure rodent models (electrical and chemical) reduced seizures to a greater extent than a current standard drug, retigabine, a nonselective Kv7 potassium opener (2), used now only experimentally.

Clinical Results

Two clinical trials evaluated azetukalner for efficacy and safety.  The first was a randomized double-blind trial of 8 weeks with escalating doses (10, 20, and 25 mg) in adults with focal onset seizures, baseline median number of 13.5 seizures per month (3).   Most importantly, a reduction in monthly seizure frequency was slightly over 50% with the highest dose compared to an 18% reduction of seizure frequency in the control group.

The second trial was an open-label trial that allowed participants in the first trial to continue with the medication (20 mg dose).  Data after one year for those who chose to continue show that nearly 15% were seizure free. After 2 years, nearly 24% were seizure free (4).  This trial had no control group. The dropout rate was approximately 25%. Nevertheless, the results are considered good in light of the difficult to treat seizures in this group of patients (4).

Treatment Related Adverse Effects

Adverse effects from this long term trial were considered mild to moderate.  They ranged from dizziness, headache, coronavirus infection, somnolence, falls and memory impairment at rates of 12.7-21.8% (4).

B)  Bexicaserin – Novel Anti-Seizure Drug Candidate

Bexicaserin is a 5HT2C serotonin receptor stimulant (agonist).  Importantly, 5HT2C is one of three serotonin receptors. Specifically, it is the one that plays a major role in seizure activity such that activation damps seizures. 

Selectivity

Bexicaserin is “super” selective (more than 1000 fold) for the 5HT2C receptor compared to the other serotonin receptors as demonstrated in vitro studies.  In this regard it’s selectivity stands out against current drugs in this category e.g. fenfluramine (5) and lorcaserin (6).  Furthermore, bexicaserin also had no effect on an extensive battery of other known brain receptors (7). In animal models of genetically or drug-induced seizure activity (zebra fish, see blog 18; mice), bexicaserin reduced seizure activity. 

Clinical Results

A phase 1b/2a randomized clinical trial tested 41 patients with developmental epileptic encephalopathies (serious epilepsy affecting brain development). Patients receiving 6 month treatment with increasing doses of bexicaserin (6-12 mg/day) exhibited reduced median motor seizure activity by slightly more than 50% compared to start of the study (8). Noteably, a Phase 3 trial (NCT06660394) with bexicaserin is currently recruiting children and adults with Dravet Syndrome, a developmental epileptic encephalopathy.

Treatment Related Adverse Effects

The two main adverse reactions affecting 20% or more of participants were somnolence and decreased appetite (8). 

C.  Soticlestat – Novel Anit-Seizure Drug Candidate

Soticlestat inhibits the metabolism of cholesterol in the brain (9).  Drug action prevents the formation of cholesterol-24 hydroxylase (24HC). 24HC is a known facilitator of nerve excitability.  Specifically, 24HC increases the concentration of glutamate, a pro-excitability transmitter. Additionally, it modulates NMDA (N-methyl-D-aspartate) “excitable”  receptors and enhances inflammation, three actions that support abnormal brain excitability (10).   Therefore, reducing 24HC  would diminish these activities.

Preclnical Results

Results in mouse models of epilepsy showed soticlestat as an efficacious antiseizure chemical entity worthy of clinical evaluation. 

Clinical Results

The most recent trial (ELEKTRA) was a phase 2 randomized double-blind trial of 126 patients for 12 weeks (up to 300 mg/d). It reported significant (median 50%) seizure frequency reduction in children and adolescents with Dravet Syndrome.  However, it did not significantly reduce seizure frequency in patients with Lennox–Gastaut syndrome, another difficult to treat epilepsy (11). An interesting asset of this drug is that efficacy can be followed by measuring the concentration of 24HC in the blood.  Thus, as 24HC declines with soticlestat use, seizure frequency also declines.

Phase 3 trial (NCT05163314) is in progress (ClinicalTrials.gov).  The clinical trial goal is the determination of safety and tolerability. This is a trial of projected 400 patients with Dravet syndrome or Lennox-Gastaut Syndrome worldwide taking solticlestat (100mg/d) for 4 years.

Treatment Related Adverse Events

Adverse effects of soticlestat were comparable to placebo with 5% experiencing lethargy and constipation to a greater degree than placebo. 

Critique 

The three novell anti-seizure drugs, working toward FDA approval, each act by a different mechanism.   Azetukalner opens a potassium channel subtype, bexicaserin stimulates a serotonin receptor subtype and soticlestat blocks cholesterol metabolism in the brain.  The variety of targets speaks to the complexity of seizures and the lack of clear knowledge about epilepsy.  All three drugs have completed phase 2 trials with evidence of efficacy and safety. 

Despite the fact that these drugs reduce seizure frequency up to 50% in different epilepsies, these drugs are far from ideal.  Selectivity of azetukalner for the Kv7,2/7.3 channels is only 4  time greater than it is for other Kv channels.  This modest selectivity most likely disappears in human, leading to general suppression of neuronal activity supporting side effects of somnolence and memory impairment.  Bexicaserin exhibits a 1000 fold selectivity for the 5HT2C receptors compared to same class subtypes.   This impressive selectivity will most likely be maintained in humans.  However, stimulation of 5HT2C does more than dampen seizures and affects multiple functions such as appetite and mood. The multiple functionality of this serotonin receptor would brings in undesired side effects.

Soticlestat is a truly novel drug that targets the destructive brain metabolite of cholesterol.  Its unique effect knocks out three potential mechanisms supporting seizures and has the greatest chance of reducing seizures with the least induction of side effects.  Furthermore, its effects can be track with measurement of 24HC in blood. 

Patients with epilepsy deserve medications that prevent seizure without blocking other vital brain activities.  Patients with epilepsy eagerly await the results of Phase 3 clinical trials for these compounds.

References

1.  Bailer M, Johannessen SI, Koepp MJ, Perucca E, Perucca P et al. Progress report on new medications for seizures and epilepsy: A summary of the 17th Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVII). II. Drugs in more advanced clinical development Epilepsia  . 2024 Oct;65(10):2858-2882.  doi: 10.1111/epi.18075. 

2.  Gunthorpe MJ, Large CH, Sankar R. The mechanism of action of retigabine (ezogabine), a first-in-class K+ channel opener for the treatment of epilepsy Epilepsia . 2012 Mar;53(3):412-24.  doi: 10.1111/j.1528-1167.2011.03365.x. 

3.  French JA, Porter RJ, Perucca E, Brodie MJ, Rogawski MA, Pimstone S, et al. Efficacy and safety of XEN1101, a novel potassium channel opener, in adults with focal epilepsy: a phase 2b randomized clinical trial. JAMA Neurol. 2023;80(11):1145–54.

4.  French JAm Porter RJ, Perucca E, Brodie MJ Rogawski MA et al. Interim analysis of the long-term efficacy and safety of azetukalner in an ongoing open-label extension study following a phase 2b clinical trial (X-TOLE) in adults with focal epilepsy Epilepsia Open. 2025 Apr;10(2):539-548. doi: 10.1002/epi4.70015. 

5.  Sourbron J, Lagae L. Fenfluramine: a plethora of mechanisms? Front Pharmacol. 2023 May 12;14:1192022. doi: 10.3389/fphar.2023.1192022

References

6.  Gutafson A, King C, Rey JA. Lorcaserin (Belviq)A Selective Serotonin 5-HT2C Agonist In the Treatment of Obesity Pharmacy and Therapeutics. 2013 Sep;38(9):525-530, 534.

7.  Ren A, Zhu Z, Lehmann J, Kasem M, Schrader TO, Dang H et al. Diazepine Agonists of the 5‑HT2C Receptor with Unprecedented Selectivity: Discovery of Bexicaserin (LP352). J. Med. Chem. 2025, 68, 10599−10618 https://doi.org/10.1021/acs.jmedchem.4c02923

8.  Kaye R, Orevillo C, Dlugos DJ, Scheffer IE. Efficacy and safety of bexicaserin (LP352) in adolescents and adult participants with developmental and epileptic encephalopathies: Results of the phase 1B/2A pacific study. In 76th Annual Meeting of the American Academy of Neurology, April 13−18, 2024, Denver, CO, 2024

9.  Nishi T, Kondo S, Miyamoto M, Watanabe S, Hasegawa S, Kondo S, et al. Soticlestat, a novel cholesterol 24-hydroxylase inhibitor shows a therapeutic potential for neural hyperexcitation in mice. Sci Rep. 2020;10(1):17081

10.  Kondo S, Murthy V, Asgharnejad M, Benitez A, Nakashima K, Hawkins N, White HS. A review of the putative antiseizure and antiepileptogenic mechanisms of action for soticlestat. Epilepsia. 2025 May;66(5):1394-1405. doi: 10.1111/epi.18287.

11.  Hahn CD, Jiang Y, Villanueva V, Zolonowska M, Arkilo D et al. A phase 2, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of soticlestat as adjunctive therapy in pediatric patients with Dravet syndrome or Lennox-Gastaut syndrome. (ELEKTRA) Epilepsia. 2022 Oct;63(10):2671-2683.  doi: 10.1111/epi.17367. 

Progress in Imaging Epilepsy

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Magnet resonance imaging (MRI), is frequently used, along with other data, to generate a diagnosis of epilepsy.   The MRI is a noninvasive imaging tool that scans the structure of the whole brain to identify abnormalities.  The MRI, alone, gives no information on physiological and pathological functions, only structure.  Fortunately, adjuncts and variants of the MRI and related techniques used to image epilepsy record changes in biological function.  Progress in imaging epilepsy improve diagnostic accuracy as well as expand understanding of epilepsy.  This blog will discuss progress in imaging epilepsy.

Progress in Imaging Epilepsy – MRI-related

MRI dependent imaging include 1) functional MRI and associated improvements,  2) diffusion MRI and 3) 1H-magnetic resonance spectroscopic imaging (MRSI).   The original MRI, using magnetic fields, detects subtle changes in brain structure, e.g. volume and contour differences in neuronal clusters particularly when newer technical adjustments are utilized (1).  Thus MRI imaging successfully identified differences in brains of normal individuals and those with temporal lobe epilepsy (1).  It is equally useful in detecting tumors and areas of traumatic brain injury.

1)  Functional MRI and advancements. 

The functional MRI (fMRI), a variant of the MRI, is also a non invasive technique.  It tracks blood oxygen levels in the brain.  The method relies on the observation that active neurons (e.g. those involved in brain-related activities such as thinking) consume more oxygen than quiescent neurons.  Thus, areas of high blood oxygen use pinpoint sites of activated functional neurons.  This technique succeeded in mapping areas involved in cognition, stress, and emotions (1).  Therefore, combining an EEG with a fMRI improves location of epileptogenic neurons triggering and supporting a seizure.  Such information is especially important in ablation surgery for drug-resistant patients with severe epilepsy (1).  fMRI is successfully used to follow the path of propagation of the seizure throughout the brain, providing evidence on how one part of the brain influences another during epilepsy progression (1).

2)  Diffusion-weighted MRI/Diffusion Tensor MRI.  

These imaging techniques measure tissue water movement in cells and surrounding space in the brain.  Each technique does it slightly differently with the oldest of the two as the diffusion-weighted MRI (3).  These techniques are advantageous in the diagnosis of pediatric epilepsy (4) and assessment of acute stroke(3) .  Research results using this imaging track and define the connectivity between neurons during brain-related activities, expanding knowledge of brain physiology (3).

3)  1H-magnetic resonance spectroscopic imaging (MRSI).

This is an old technique that is generating renewed interest due to its enhanced magnetic resonance sensitivity (5).  MRSI detects substances whose molecular components contain high amounts of 1H protons.  The main substances are N-acetyl-aspartate (NAA), creatine, and choline.  Results of numerous studies show that the ratio of NAA to creatine provides information on abnormal neuronal activity associated with oxidative stress.  This imaging opens up research on the relation between oxidative stress and neurotransmitters such as GABA (gamma amino butyric acid), a neurotransmitter implicated in epilepsy (5).

Progress in Imaging Epilepsy – Radioactive Imaging.

In contrast to the MRI, PET and SPECT are invasive imaging methods that inject radioactive substances to study brain activity in disease.

1)  PET stands for Positron Emission Tomography.

This imaging technique employs a positron emitting chemical (tracer) such as a radioactive variant of glucose (fluorodeoxyglucose).  Active neurons and auxiliary cells take up the sugar thus highlighting an area of brain activity.  This is used to identify tumors which are more metabolically active than normal tissue.  PET is also valuable in tracing blood flow in metabolic regions during a seizure.  While capture of a seizure during a PET scan is rare, measurement of activity between seizures is more likely and provides important information.  Here, areas of low metabolism (hypometabolism) indicate sites of epileptic origin and are useful aids in surgical ablations (1).

The PET also uses radioactive analogues of neurotransmitters to uncover changes in brain receptor activity in epilepsy (6).  Additionally, PET imaging reveals an increase in a specific marker of brain inflammation, the translocator protein (TSPO).  TSPO is elevated in epilepsy (7).  Its elevation indicates that auxiliary cells (glial cells) are active and contributing to brain inflammation (8).  See earlier blog on the role of inflammation in epilepsy (Neuroinflammation of Epilepsy – new diagnostic tools)

2)  SPECT stands for Single photon emission computed tomography. 

This  imaging technique is similar to PET but differs in that the radioactive tracers emit a different type of radiation.  Gamma rays are detected by SPECT.  For epilepsy diagnosis, SPECT is used secondarily to PET (9).  It is considered important for surgical candidates with drug resistant epilepsy in which no structural lesions are found.  This technique is highly successful in localization of  the site of seizure origin in pediatric epilepsy (10).

Progress in Imaging Epilepsy – Magnetoencephalography

Magnetoencephalography (MEG) differs radically from the above discussed techniques.  Specifically, it does not use magnetism or radioactivity to “shake up or interact with” with molecules in brain to define structure and function (11).  Rather, the MEG detects magnetic fields generated or given off from nerves after they transmit their signal (termed postsynaptic activity).  Because magnetic waves are received without distortion, the location of epileptogenic foci are more accurately identified.   MEG is considered an advanced version of the EEG.  Similar to the EEG, it is non invasive.  However, the EEG records electrical activity without the ability to assign origin to such activity.  In contrast, the MEG accurately locates the origin of abnormal nerve activity.  MEG associated with PET or MRI data is of great assistance in surgical ablations for severe epilepsy (11).  Additionally, findings from this technique suggest the existence of connectivity between several areas of the brain during seizures, expanding understanding of the complexity of epilepsy (1).  

Conclusions

This blog describes a number of sophisticated imaging techniques and methods used to assist with the diagnosis of epilepsy, illustrating progress in imaging epilepsy.  These include variations of the classic MRI, radioactive imaging and an upgraded version of the EEG.  The majority of these methods provide critical data to pinpoint epileptogenic foci for surgical ablations in cases of drug-resistant severe epilepsy.  Although accessed less frequently for research, the insights that have been gained thus far are invaluable.   These techniques offer potential for deeper understanding of the pathology of epilepsy and hence better therapy and a possible cure.

References http://pubmed

1.  Goodman AM, Szaflarski JP. Recent Advances in Neuroimaging of Epilepsy.  Neurotherapeutics. 2021 Apr;18(2):811-826. doi: 10.1007/s13311-021-01049-y.

2.   Chang C, Huang C, Zhou N, Li SX, Ver Hoef L, Gao Y. The bumps under the hippocampus. Hum Brain Mapp . 2018 Jan;39(1):472-490.  doi: 10.1002/hbm.238563. 

3.  Ranzenberger LR, Das JM, Snyder T.  Diffusion Tensor Imaging  StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan. 2023 Nov 12.

4   Szmuda M, Szmuda T, Springer J et al., Diffusion tensor tractography imaging in pediatric epilepsy – A systematic review.  Neurol Neurochir Pol . 2016;50(1):1-6.  doi: 10.1016/j.pjnns.2015.10.003. 

5 Pan JW, Kuzniecky RI Utility of magnetic resonance spectroscopic imaging for human epilepsy. .Quant Imaging Med Surg. 2015 Apr;5(2):313-22. doi: 10.3978/j.issn.2223-4292.2015.01.036.

6.  Sarikaya I. PET studies in epilepsy.  Am J Nucl Med Mol Imaging. 2015 Oct 12;5(5):416-30. eCollection 2015.

7.  Galovic, M, Koepp, M. Advances of molecular imaging in epilepsy. Curr Neurol Neurosci Rep  2016 Jun;16(6):58.  doi: 10.1007/s11910-016-0660-7.

8.  Zhang L, Hu K, Shao T, Hou L, Zhang S, Ye W, Josephson L, Meyer JH, Zhang MR, Vasdev N, Wang J, Xu H, Wang L, Liang SH Recent developments on PET radiotracers for TSPO and their applications in neuroimaging.  .Acta Pharm Sin B. 2021 Feb;11(2):373-393. doi: 10.1016/j.apsb.2020.08.006.

9.  Cendes F, Theodore WH, Brinkmann BH, Sulc V, Cascino GD.Neuroimaging of epilepsy. Handb Clin Neurol. 2016;136:985-1014. doi: 10.1016/B978-0-444-53486-6.00051-X.

10.  Juhász C, John F.Utility of MRI, PET, and ictal SPECT in presurgical evaluation of non-lesional pediatric epilepsy.Seizure. 2020 Apr;77:15-28. doi: 10.1016/j.seizure.2019.05.008. 


11.  Pan R, Yang C, Li Z, Ren J, Duan Y. Magnetoencephalography-based approaches to epilepsy classification.  Front Neurosci. 2023 Jul 12;17:1183391. doi: 10.3389/fnins.2023.1183391

Neuroinflammation of Epilepsy – new diagnostic tools

Current Research Advances, , ,

Key Mediators of Neuroinflammation

Over the past ten years, the number of research papers focused on neuroinflammation of epilepsy has escalated dramatically (Ngadimon et al., 2024).  Thus, neuroinflammation is central to both the initiation (epileptogenesis) of epilepsy and the support for repetitive seizures.  A great deal is known about the inflammatory pathways active in epilepsy (Aguilar-Castillo et al., 2024; Ngadimon et al., 2024).  Furthermore, several key mediators of neuroinflammation are now potential biomarkers of epilepsy (Aguilar-Castillo et al., 2024).  These select biomarkers are possible new diagnostic tools poised to replace the traditional EEG. 

This blog will discuss one of the key mediators of neuroinflammation of epilepsy, termed High-Mobility Group Box 1, also known as HMGB1 (Aguilar-Castillo et al., 2024; Ngadimon et al., 2024; Chen et al., 2023) .  HMGB1 has the potential to be an innovative and relevant diagnostic tool to identify and monitor the disease of epilepsy.

Unmet Medical Needs – Biomarkers and Selective Drugs

Several key neuroinflammatory mediators including HMGB1 and others are present in serum and importantly are associated with the severity and frequency of seizures (see studies below) (Ngadimon et al, 2024).  The ability of the traditional EEG to diagnosis new onset epilepsy is poor and its predictive capability for repeat seizures is limited.  It is, therefore, critical to pursue research to fill this unmet medical need and to identify novel molecules exclusive to epilepsy as valid diagnostic and prognostic tools.

Key Mediators of Neuroinflammation as drug targets

Moreover, select neuroinflammatory mediators and their target receptors have potential as targets for new drug therapy (Maroso et al., 2010).  Current anti-seizure drugs, although there are many, have adverse side effects that cause many patients to discontinue use (Chen et al., 2023).  These drugs suppress seizures but do nothing about the progression of the disease.  Furthermore, 30% of epileptic patients do not benefit from present day drugs. They are considered drug-resistant.  Thus, there is a need to develop more selective drugs.  Therefore, focus on development of drugs that inhibit the epilepsy-promoting effects of key mediators of neuroinflammation should prove of value.

Neuroinflammation of epilepsy – instigator?

Neuroinflammation is an inflammatory disturbance in and among the cells of the brain.  “Increasing evidence indicates that neuroinflammation is a common consequence of epileptic seizure activity, and also contributes to epileptogenesis as well as seizure initiation (ictogenesis) and perpetuation.” (Webster et al., 2017).  Approximately half of all acquired epilepsies occur following a prior neurological injury that produces neuroinflammation.  Neurological injuries are injuries such as a brain tumor/infection, traumatic brain injury, or exposure to destructive nerve agents (Klein et al., 2018; Chen et al., 2023).  Neuroinflammation is also the common denominator between epilepsy and sleep disorders (see blog 11)

Animal Models, Human Epileptic Tissue

Results of studies in animal models of epilepsy and data from human epileptic tissue specimens, define the brain pathways and mechanisms of neuroinflammation.  In general, a latent phase follows a brain injury and progresses to a chronic phase.  These changes eventually heighten the excitability of nerves, giving rise to seizures.  Neuroinflammation is characterized by abnormal alterations in brain support cells e.g. astrocytes and glial cells, harmful modifications in the blood-brain barrier (making it more porous susceptible to entry of unwanted cells and proteins), infiltration of immune cells, nerve cell death and reorganization of remaining neurons (Klein et al., 2018; Chen et al., 2023)(see Figure below). 

Importantly, these revisions produce an abundance of significant pro-inflammatory substances whose effects modify nerve activity favoring excitability.  High-Mobility Group Box 1 (HMGB1) is among one of the significant pro-inflammatory substances. Data show its amplified presence enhances nerve excitability and participates in continued hyper excitability (Maroso et al., 2010; Kamasak et al., 2020).

High-Mobility Group Box 1 (HMGB1) -Major Culprit?

HMGB1 is a nuclear protein with a normal activity of assisting DNA in gene expression (“turning genes off and on”), maintenance and repair.  Therefore, residing in the nucleus it remains beneficial.  However, stress-induced movement to the cytoplasm and the extracellular fluid renders it harmful.  Thus, when released from cells, actively or via cell death, HMGB1 acts as a pro-inflammatory initiator binding to one of two receptors (Toll-like Receptor 4, TLR4 and receptor for advanced glycation endproducts, RAGE) (Paudel et al., 2018; Chen et al., 2023). 

HMGB1 Consequences

This interaction sets off a cascade of changes that continue to generate other proinflammatory factors (cytokines, chemokines, growth factors, lipids) that support continued inflammation, keep the vicious cycle going by enabling more HMGB1 release and induce unwanted nerve hyperactivity. Thus, HMGB1 is one of the key mediators of neuroinflammation.

HMGB1 – Role in humans with epilepsy

As reviewed by Aronica and Crino (2011), there are several studies using resected (surgically removed) human epilepsy foci.  These specimens clearly show the presence of neuroinflammation.  Compared to normal brain tissue, specific inflammation mediators and their receptors are present in large amounts in tissue from epilepsy patients.  It is suggested that these distinct changes account for the neuroinflammation and are responsible for promotion of neuronal hyperactivity.  In particular, elevated levels of HMGB1and its receptor TLR4 were identified in human epilepsy foci, specifically in proactive astrocytes and microglia  (Aronica and Crino, 2011).  This positions HMGB1 as one of the key mediators of neuroinflammation.

Biochemical Analysis

More recently, biochemical analysis of  brain tissue removed from patients with intractable epilepsy compared to normal tissue showed HMGB1 not only in the nuclei of  neurons and glia cells (normal tissue location) but also in the cytoplasm where its release would be expected (Shi et al., 2018).  HMGB1, its two receptors (TLR4, RAGE) were significantly elevated in tissue from epilepsy patients compared to normal controls (Shi et al., 2018).

Activated and possibly damaged brain cells release HMGB1 in epileptic regions and, therefore, it should be detectable in serum.  Indeed, three studies reported elevated HMGB1 levels in children with epilepsy (Zhu et al., 2018), adults with drug resistant epilepsy (Walker et al., 2022) and case-control study of 105 epilepsy patients compared to 100 healthy controls (Kan et al, 2019). 

Serum Levels of HMGB1

The insights gained from these studies are important. The first study measured HMGB1 24 hours prior to a seizure.  Thus, the high levels of HMGB1 (and other inflammatory mediators) was predictive of seizure onset and frequency in children (Zhu et al., 2018), a prognostic benefit.  In the second study, drug-resistant epilepsy patients showed higher HMGB1 levels compared to those controlled with drugs and normal controls.  This suggests a possible screening tool to identify those resistant to standard drugs, all of which dampen ion channels and have no effect on neuroinflammation (Walker et al, 2022). 

Significant Human Study

The third study found that the levels of HMGB1 and TLR4 were higher in patients with more than 3 seizure/month and these levels additionally correlated with duration of the seizure of greater than 5 minutes.  HMGB1 levels were independent of the type of seizure (partial, general) or length of the disease (Kan et al., 2019).  These are important findings but are correlative.  Additional studies such as long term clinical trials are required to establish cause-and-effect. 

Conclusions

Clearly there is a need for validated and precise diagnostic tools to promptly and correctly identify the beginning stage and progression of epilepsy.  Misdiagnosis or delayed diagnosis prove fatal.  The neuroinflammatory mediator, HMGB1, is a reasonable diagnostic and prognostic candidate since it is one of the key mediators of neuroinflammation.  Initial stages of epilepsy exhibit higher levels of HMGB1 and serum levels correlate with onset, frequency and duration of epilepsy in humans.  However, the information at present, although promising, is limited and requires more studies, better assays to detect all forms of HMGB1 and definitely a serious research effort with a large clinical trial.

Figure By: Paudel YN, Shaikh MF, Chakraborti A, Kumari Y, Aledo-Serrano Á, Aleksovska K, Alvim MKM, Othman I.HMGB1: A Common Biomarker and Potential Target for TBI, Neuroinflammation, Epilepsy, and Cognitive Dysfunction. Front Neurosci. 2018 Sep 11;12:628. doi: 10.3389/fnins.2018.00628.

References  (http://Pubmed)

1.  Ngadimon IW, Shaikh MF, Mohan D, Cheong WL, Khoo S. Mapping epilepsy biomarkers: a bibliometric and content analysis.  Drug Discov Today. 2024 Dec;29(12):104247. doi: 10.1016/j.drudis.2024.104247.

2.  Aguilar-Castillo MJ, Cabezudo-García P, García-Martín G, Lopez-Moreno Y, Estivill-Torrús G, Ciano-Petersen NL, Oliver-Martos B, Narváez-Pelaez M, Serrano-Castro PJ.A Systematic Review of the Predictive and Diagnostic Uses of Neuroinflammation Biomarkers for Epileptogenesis. Int J Mol Sci. 2024 Jun 12;25(12):6488. doi: 10.3390/ijms25126488.

3.  Chen Y, Nagib MM, Yasmen N, Sluter MN, Littlejohn TL, Yu Y, Jiang J.  Neuroinflammatory mediators in acquired epilepsy: an update Inflamm Res. 2023 Apr;72(4):683-701. doi: 10.1007/s00011-023-01700-8. 

4.  Maroso M, Balosso S, Ravizza T, Liu J, Aronica E, Iyer AM, et al. Toll-like receptor 4 and high-mobility group box-1 are involved in ictogenesis and can be targeted to reduce seizures. Nat Med. 2010;16:413–419. doi: 10.1038/nm.2127 Webster KM, Sun M, Crack P, O’Brien TJ, Shultz SR, Semple BD Inflammation in epileptogenesis after traumatic brain injury. .J Neuroinflammation. 2017 Jan 13;14(1):10. doi: 10.1186/s12974-016-0786-1.

5.  Klein P, Dingledine R, Aronica E, Bernard C, Blümcke I, Boison D, Brodie MJ, Brooks-Kayal AR, Engel J Jr, Forcelli PA, Hirsch LJ, Kaminski RM, Klitgaard H, Kobow K, Lowenstein DH, Pearl PL, Pitkänen A, Puhakka N, Rogawski MA, Schmidt D, Sillanpää M, Sloviter RS, Steinhäuser C, Vezzani A, Walker MC, Löscher W Commonalities in epileptogenic processes from different acute brain insults: Do they translate?.Epilepsia. 2018 Jan;59(1):37-66. doi: 10.1111/epi.13965.

6.  Kamaşak T, Dilber B, Yaman SÖ, Durgut BD, Kurt T, Çoban E, et al. HMGB-1, TLR4, IL-1R1, TNF-α, and IL-1β: novel epilepsy markers? Epileptic Disord. (2020) 22:183–93. 10.1684/epd.2020.1155.

7. Aronica E, Crino PB. Inflammation in epilepsy: clinical observations. Epilepsia. 2011;52(Suppl 3):26–32. doi: 10.1111/j.1528-1167.2011.03033.x.

8.  Shi Y, Zhang L, Teng J, Miao W. HMGB1 mediates microglia activation via the TLR4/NF-κB pathway in coriaria lactone induced epilepsy. Mol Med Rep. (2018) 17:5125–31. 10.3892/mmr.2018.8485.

9.  Zhu M, Chen J, Guo H, Ding L, Zhang Y, Xu Y. high mobility group protein B1 (HMGB1) and Interleukin-1β as prognostic biomarkers of epilepsy in children. J Child Neurol. (2018) 33:909–17. 10.1177/0883073818801654. 

10.  Walker LE, Sills GJ, Jorgensen A, Alapirtti T, Peltola J, Brodie MJ, Marson AG, Vezzani A, Pirmohamed M. High-mobility group box 1 as a predictive biomarker for drug-resistant epilepsy: a proof-of-concept study. Epilepsia. 2022;63:e1–6. 10.1111/epi.17116.

11.  Kan M, Song L, Zhang X, Zhang J, Fang P. Circulating high mobility group box-1 and toll-like receptor 4 expressions increase the risk and severity of epilepsy. Braz J Med Biol Res. 2019. 10.1590/1414-431X20197374.

12. Paudel YN, Shaikh MF, Chakraborti A, Kumari Y, Aledo-Serrano Á, Aleksovska K, Alvim MKM, Othman I.HMGB1: A Common Biomarker and Potential Target for TBI, Neuroinflammation, Epilepsy, and Cognitive Dysfunction. Front Neurosci. 2018 Sep 11;12:628. doi: 10.3389/fnins.2018.00628.

Zebrafish – a valuable animal model

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The zebrafish (Danio rerio), approximately 2-4 cm in length, has become a valuable animal model for investigations of neurological diseases and for use in high intensity screening to discover disease-ameliorating drugs.  In particular, this tiny non-mammalian animal has been of use in research into the genetics and pathophysiology of epilepsy and in the evaluation of anti-seizure drugs.  This blog will discuss this model and some of its contributions to understanding epilepsy.

Animal Models

There are many experimental models of epilepsy.  The greatest research effort has focused on rodent models of epilepsy (chemically or electrically-induced seizure, acute or chronic).  Interest in both experimental and natural models of epilepsy in the non-human primates (monkeys) has risen in recent years as has interest in smaller, non-mammalian models (amoeba, roundworm, fruit fly, zebrafish).  To be of scientific value, scientists must rigorously validate all models.  They must demonstrate neuronal electrical activity, neurotransmitter release, gene expression and response to antiseizure drugs comparable to that observed in patients with epilepsy.  As a result, animal models have contributed significantly to the identification of the multiple causes of epilepsy, genetic and environmental and are absolutely essential to the development of safe and effective antiseizure drugs.

Zebrafish Attributes that Make for a Successful Animal Model

Although rodent models of epilepsy have contributed considerably to our understanding of this disease,  rodents are expensive to breed, house and treat.  In contrast, the zebrafish is inexpensive to breed, maintain and treat.  Thus, large numbers are readily cared for with minimal expense.  Zebrafish mature quickly (~3 months), are highly fertile, giving rise to large numbers of offspring and can live in captivity up to 5 years.  The immature form, the larva, is transparent facilitating visual experimentation especially in observing gene expression and nerve activity.  Larvae and embryos are ideal for screening of large numbers of drugs for antiseizure activity.

Additionally and importantly, the zebrafish model relates well to rodent models and patients with epilepsy.  Firstly, 77% of zebrafish genes are similar to those in humans and approximately 80% of disease-associated genes are also present in zebrafish.  EEG recordings in drug-induced seizures in larvae and adult fish are similar to those observed in patients with epilepsy. 

Zebrafish mutants exist with alterations in genes involved in a number of human epileptic syndromes e.g. Dravet’s syndrome (see blog 17). Zebrafish mutants also show similar electrophysical activity as well as responses to anti-seizure drugs as evident in humans.  Additionally, zebrafish express brain neurotransmitters such as gamma-aminobutyric acid, glycine and acetylcholine. These are the same ones involved in human epilepsy. Neurotransmitters in zebrafish increase or decrease in response to seizure-producing and anti-seizure drugs as reported for rodents.

Contribution from Zebrafish Mutants

Many rare and not so rare genetically driven epilepses in humans have been successfully developed in zebrafish mutants.  One epilepsy of interest is Dravet syndrome, a grave pediatric epilepsy with severe seizures and associated cognitive deficits.  The disease origin is attributed in large part to a mutated neuronal sodium channel.  Zebrafish mutants lacking key elements of the sodium channel as in Dravet syndrome were developed and characterized (Baraban et al., 2013).  Mutant zebrafish exhibit abnormal brain electrical activity, related hyperactive locomotion and convulsions.  Furthermore, anti-seizure drugs that reduce seizures in Dravet syndrome also reduce seizures in zebrafish. Moreover, those that are ineffective in Dravet syndrome fail in mutated zebrafish. 

Zebrafish Mutants and Drug Evaluation

Using this model, over 300 chemicals and known drugs were tested (Baraban et al., 2017).  One drug, chemizole, an FDA approved antihistamine with a good safety profile, was highly effective.  This is a surprise but significant finding.   Since other antihistamines were ineffective, the mechanism of action of chemizole in seizure reduction suggests a unique unknown target. This is an opportunity to develop a new potentially novel antiseizure drug for Dravet syndrome.

Contribution from the proconvulsant-treated Zebrafish

The proconvulsant-treated zebrafish (also shortened to the PTZ-treated zebrafish) is a validated and reliable model of epilepsy.  It is used to identify the initial neuronal changes in epilepsy, to identify new anti-seizure drugs and recently to study the negative role of seizures on cognition.  PTZ (pentylenetetrazole) is a proconvulsant. Researchers treat zebrafish with PTZ to generate seizure activity comparable to generalized absence and myoclonic seizures in humans (Gawel et al., 2020).  Specifically, scientists anesthetize the zebrafish and inject the zebrafish intraperitonally (space between skin and intestines) with PTZ and/or an anti-seizure drug. Scientists then return the zebrafish to the testing tank for observations depending on the experimental protocol.   PTZ-induced seizures in zebrafish are dose and time-dependent and ameliorated by anti-seizure drugs such as valporic acid and diazepam (see blog 5).  Changes in locomotor activity following PTZ administration correlates with EEG activity.  

PTZ (proconvulsant)-treated Zebrafish results

As with Zebrafish mutants, researchers use the PTZ-treated zebrafish to screen for novel anti-seizure drugs.  Another interesting use is the study of the negative role of seizures in memory and learning.  Kundap et al., (2017) approached this by developing a T-maze for fish to evaluate memory and behavior.  In this study, researchers collected data on seizure activity, memory, neurotransmitter release and gene expression.  Interestingly, not only did seizure activity affect performance in the T-maze but the anti-seizure drugs that reduced seizure activity also reduced memory.  Tested drugs were phenytoin (Dilantin) oxcarbazepin (Trileptal), gabapentin (Gralise), diazepam (Diastat), rivastigmine (used in dementia ).  The authors conclude that this study provides “proof-of-concept” that the PTZ-treated zebrafish is a valuable model to study the negative effects of repetitive seizures on cognition.  These results emphasize the need to use cautiously those anti-seizure drugs that are additive to the harmful effects of seizure on memory.

Zebrafish Rendition

Conclusions

Investigations with validated animal models are an essential strategy to reveal the genetics and pathophysiology of epilepsy. Also, validated animal models are necessary to develop candidate drugs to eliminate seizures and cure epilepsy.  Although the most frequently used models for epilepsy are rodent models, the smaller, less expensive and equally useful model is the zebrafish.  Its many attributes and its validated relevance to genetics and etiology of human epilepsies may make it the model of choice for anti-seizure drug screening.

References

Baraban SC, Dinday MT, Hortopan GA. Drug screening in Scn1a mutant zebra-fish identifies clemizole as a potential Dravet syndrome treatment. Nat Com-mun 2013;4:2410.

Cunliffe VT et al., Epilepsy research methods update. Understanding the causes of epileptic seizures and identifying new treatments using non-mammalian model organisms Seizure 24 (2015) 44–51.

Gawel K et al., Seizing the moment: Zebrafish epilepsy models. Neuroscience and Biobehavioral Reviews 116 (2020) 1–20.

Kandratavicius L et al.,  Animal models of epilepsy: use and limitations.   Neuropsychiatric Disease and Treatment (2014):10 1693–1705.

Kundap UP et al., Zebrafish as a Model for Epilepsy-Induced Cognitive Dysfunction: A Pharmacological, Biochemical and Behavioral Approach Front. Pharmacol. 8:515, 2017.

Niemyer JE et al., Seizures initiate in zones of relative hyperexcitation in a zebrafish epilepsy model Brain (2022): 145; 2347–2360.

Precision Medicine – Promising Future

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Introduction

There is a rising number of epilepsies that have been associated with genetic mutations called genetic variants (see Blog 14) .  For example, some of these epilepsies result from gene variants in ion channels that produce a loss of function or a gain of function.  Such changes promote seizures and other neurological deficits.  Specifically, the common gene variants account for 30% of adult general epilepsies. As more genetic expertise is developed, this number is expected to significantly increase.  Ongoing research from Ingo Helbig and collaborators at the Children’s Hospital of Philadelphia, Perelman School of Medicine and other University neurological departments) suggests that precision medicine is the promising future therapy of genetic-based epilepsies.

Precision Medicine

As reviewed by Knowles et al., (2022), precision medicine is an encompassing approach to optimal treatment.  In particular, it is based on classifying patients according to measurable biology, susceptibility to disease, and response to treatment to assure an efficacious intervention for those who would benefit and avoid those who would not.  For genetic epilepsies, “ideal precision treatment would correct a well-defined genetic mechanism in the context of individualized factors, to impart freedom from seizures and comorbidities” (Knowles et al., 2022).  However, this calls for integration of genetic analysis, natural history and clinical data into searchable databases.  Already, genetic testing alone yields better treatment and less hospitalizations.  Adding natural history and clinical data to genetic analysis would achieve considerably more treatment success.

Achievements Toward Precision Medicine

Identification of genetic variants in certain epilepsies allows for the application of molecular biology techniques to interfere with unwanted mRNA produced by genetic variants.  Therefore, appropriately designed oligonucleotides as well as vector-promoter-gene complexes successfully treat animal models of epilepsy. Currently, evaluation of the latter is ongoing in a clinical trial (NCT05419492) (https://clinicaltrials.gov/ct2/show/) for a genetic epilepsy. 

The discovery of the gene termed SCN8A exemplifies the feasibility of  rapid trajectory from gene identification to precision medicine.  Specifically, SCN8A (voltage-gated sodium channel gene) was discovered in 1995 in mice. Later, its pathological variants were associated with epileptic encephalopathies (seizures with neurological pathology).  By 2019, following intense research, the testing of a specific sodium channel inhibitor (NBI-921352) for the genetic variant was initiated.  Presently, “NBI-921352 is entering phase II proof-of-concept trials for the treatment of SCN8A-developmental epileptic encephalopathy (SCN8A-DEE) and adult focal-onset seizures” (Johnson et al., 2022).  Although this is impressive, “coordinated and systematic streamlining of the epilepsy precision medicine pipeline” from gene discovery to effective therapy is the essential goal (Knowles et al., 2022).

Challenges for Precision Medicine

Technological improvements in genome-wide association studies (GWAS) have facilitated the ability to screen large groups of patients to detect genetic variants associated with disease.  The result is the creation of large available, searchable databases of genetic variants.  However, not only must the gene variant associated with the disease be considered but more importantly, the unique expression of the gene variant in a particular patient must be defined. 

The expression of a gene variant is termed the phenotype of the disease. The phenotype includes all of the clinical observations and measurements in the patient relevant to the epilepsy. Therefore, gene expression may take many forms creating multiplicities and complexities of expression (heterogeneity) from patient to patient. Hence, the correct association of a gene variant with a defined phenotype poses a serious challenge.  According to Helbig and Tayoun, (2016) accurately defining the phenotype of a rare genetic variant, e.g. STXBP1 producing an epileptic encephalopathy represents a “hurdle” due to the phenotypic spectrum that it produces. 

To address this challenge, Helbig et al., (2019) characterized the phenotype of patients with “missense variant in AP2M1” (coding a protein needed for uptake mechanisms on the cell membrane).  The use of the searchable database, Human Phenotype Ontology, set up in 2008 to formalize the phenotypes of all diseases, enhanced this work.  More recently, the International League Against Epilepsy added neurological data and guidelines to it (Kohler et al., 2021).  This database presents “a standardized format to provide both terminology and semantics to a broad range of phenotypic features, including neurological features” (Helbig and Tayoun, 2016).  Consequently, with this type of analysis, researchers (Helbig and Tayou) were able to show “significant phenotypic overlap in individuals with the recurrent AP2M1”. 

Conclusions

To successfully treat epilepsy and its comorbidities both the genotype and phenotype of the epilepsy requires accurate assessment.  Researchers at Children’s Hospital of Pennsylvania and the Perelman School of Medicine and their collaborators are focused on this assessment.  The challenge lies in the interpretation of the epilepsy phenotype since both severe and less severe epilepsies are driven by the same genetic variants.  Sorting out this phenotypic heterogeneity will be worthwhile and lead to benefits of precision medicine for all patients.

References (pubmed)

Clatot J et al., SCN1A gain-of-function mutation causing an early onset epileptic encephalopathy. Epilepsia.64(5):  1318-1330, 2023.

Ganesan S, et al., A longitudinal footprint of genetic epilepsies using automated electronic medical record interpretation. Genet Med. 22(12):  2060-2070, 2020.

Helbig I et al., A Recurrent Missense Variant in AP2M1 Impairs Clathrin-Mediated Endocytosis and Causes Developmental and Epileptic Encephalopathy.  Am J Hum Genet .104(6):  1060-1072, 2019.

Helbig I, Tayoun ANA. Understanding Genotypes and Phenotypes in Epileptic Encephalopathies. Mol Syndromol  7:  172–181, 2016.

Kohler S et al.,  Human Phenotype Ontology in 2021, Nucleic Acids Research  49, Database issue D1207–D1217, 2021.

Knowles JK et al., Precision medicine for genetic epilepsy on the horizon: Recent advances, present challenges, and suggestions for continued progress. Epilepsia. 63(10):   2461–2475, 2022.

Lewis-Smith D et al., Phenotypic homogeneity in childhood epilepsies evolves in gene-specific patterns across 3251 patient-years of clinical data. Eur J Hum Genet. 29(11):  1690-1700, 2021.

Seiffert S et al., KCNC2 variants of uncertain significance are also associated to various forms of epilepsy. Front Neurol. 14: 1212079, 2023.

Xian J et al., Delineating clinical and developmental outcomes in STXBP1-related disorders. medRxiv. 2023 May 11;2023.05.10.23289776. doi: 10.1101/2023.05.10.23289776. Preprint

Early Detection of Seizures

Current Research Advances, , , ,

For decades,  the early detection of a seizure was a serious research effort.  It was obvious that if a seizure could be detected before its initiation, the patient would be better prepared to seek help to suppress the seizure.  However, early detection of a seizure with a lead time of hours proved to be unattainable.  Over the past decade, early detection of a seizure within minutes not hours of its initiation seemed a more reasonable objective.  This blog will focus on the state of research on early detection of seizures with advances developed by the epilepsy laboratory at Johns Hopkins University.

Introduction

As reviewed by Jouny et al., (2011), “The window of opportunity is the time of the earliest detectable changes in the EEG and the onset of disabling clinical symptoms”.  Thus, this provides a definition of early detection.  It may sound straightforward but there are numerous challenges to early detection of seizures. Jouny et al., reviews some of them.

1. Early detection of seizures –  Sensitivity and specificity

Early detection is just that.  Firstly, it must detect the earliest change in the electrical (neuronal) activity that leads to a seizure (called a true positive) and not an electrical event that would not lead to a seizure (called false positive).  Stated another way, the seizure is termed the ictal event and non seizure activity is the interictal activity.  Secondly, early detection must distinguish between lots of interictal activity and a smaller amount of ictal activity.  Many times initially there is little neuronal difference in the two.  Therefore, both sensitivity and specificity are required elements of any measurement targeting early detection of a seizure.

2.  Early detection of seizures – Capacity of microelectrodes.  

Microelectrodes in high density arrays are useful in obtaining detailed data of abnormal neuronal activity (termed pathological high frequency oscillations) indicative of  localized seizures. Specifically, researchers attach microelectrodes to the EEG or intracellular electrodes to capture as much information as possible.  Seizures that spread over extensive areas, unfortunately, surpass the present day recording capabilities of the microelectrode arrays.

3.  Early detection of seizures – Sampling rate.

Higher sampling rates are desirable but this produces more data for analysis.  This requires more powerful computers and better electronics.  Improvements here are needed to detect unique potential changes that distinguish the initiation of the seizure and the seizure itself from all the electrical activity in between.

Current Advances in Early Detection of Seizures.

Early detection devices depend on what is called support vector machines (SVM) which are a type of machine learning algorithms.  “Several algorithms have been developed for early-seizure-onset detection with real-time capabilities for scalp-EEG” (Ehrens et al., 2022).  In particular, they include early detection algorithms worldwide from labs in the Netherlands (Bogaarts et al., 2016); in India (Sridevi et al., 2019); in Italy (Chisci et al., 2010); in Austria/Netherlands (Fürbass et al., 2015); in Germany (Meier et al., 2008; Manzouri et al., 2021); in Canada (Saab and Gotman, 2005) and in the US, (Minasyan et al., 2010, Yidiz et al., 2022, Ehrens et al., 2022). 

Application of early detection algorithms

Early detection devices are appropriately evaluated in an epilepsy monitoring unit (EMU).  The EMU needs to gather reams of data for precise surgical intervention in patients with epilepsy that are resistant to drugs.  The Johns Hopkins Epilepsy Laboratory developed an “dynamical and self-adapting algorithm” (Ehrenss et al., 2022) which detects in real time the seizure phase of early onset as well as the seizure itself.  It is patient specific and does not require prior EEG training.  Basically, the ” algorithm uses a dynamic training set, based on a 20-min dataset that is updating every second” and ” requires no prior training because the algorithm compares the past 20 minutes of activity with the current activity and looks for novelty” (Ehrens et al., 2022)  A processing time of 0.5 seconds allows  algorithm processing, removal of artifacts, and extraction of essential features in the 20 minute learning session.

One-class SVM in early detection of seizures.

This algorithm, referred to as a one-class SVM, was tested in 35 patients with epilepsy (male: female, 62%:38%, 34 years average age) in the Johns Hopkins Hospital EMU.  “Patients were implanted intracranially with a combination of subdural grids, strips and/or depth electrodes to record cortical EEG and stereo EEG signals respectively ” (Ehrens et la., 2022).   For other information on intracranial recordings, check out Blog 10.

As presented above, the algorithm collected EEG data, eliminated non-neural artifacts and identified features essential to seizure identification  This preprocessing trains the one-class SVM and determines novelty.  The output is “post processed” such that it will then identify and signal the detection of an epileptiform event in real time. 

Although multiple SVM configurations were evaluated, the single SVM configuration yielded the best results.  The John Hopkins Laboratory SVM achieved a rate of 87% for true positives and a rate of 1.25% for false positive/hour.  That is, the SVM algorithm detected a seizure correctly 87% of the time and was wrong 1.25% of the time.  The true positive rate increased another 6% points and the false positives declined by half with removal of artifacts post analysis.  The mean detection latency (early detection) was 10.4 seconds. 

Conclusions

There is definitely a need for devices capable of early detection of seizures.  In the EMU, early detection alerts the staff and enables immediate treatment of the patient with epilepsy.  Outside the EMU, an early detection device would dramatically enhance the quality of life of patients with epilepsy.  The algorithm (one class SVM) is moving closer to achieving these goals.  Presently, 100% sensitivity of early detection is achievable in 74% of patients in the EMU setting with the unique algorithm developed at Johns Hopkins Laboratory (Ehrens et al., 2022). 

References (pubmed)

Bogaarts JG et al.,. Improved epileptic seizure detection combining dynamic feature normalization with EEG novelty detection. Med Biol Eng Comput  54:1883–92, 2016.

Chisci L. et al., Real-time epileptic seizure prediction using AR models and support vector machines. IEEE Trans Biomed Eng. 57(5):1124-32, 2010.

Ehrens et al., Dynamic training of a novelty classifier algorithm for real-time detection of early seizure onset.  Clin Neurophysiol.  135: 85–95, 2022.

Furbass F. et al., Prospective multi-center study of an automatic online seizure detection system for epilepsy monitoring units Clin Neurophysiol. 126(6):1124-1131, 2015.

Jouny CC. et al., Improving Early Seizure Detection Epilepsy Behav.  22(Suppl 1): S44–S48, 2011.

Manzouri F et al., A Comparison of Energy-Efficient Seizure Detectors for Implantable Neurostimulation Devices Front Neurol 12:703797, 2022.

Meier R et al., Detecting epileptic seizures in long-term human EEG: a new approach to automatic online and real-time detection and classification of polymorphic seizure patterns J Clin Neurophysiol. 25(3):119-31, 2008.

Minasyan GR et al., -specific early seizure detection from scalp electroencephalogram J Clin Neurophysiol. 27(3):163-78, 2010.

Saab ME, Gotman J. A system to detect the onset of epileptic seizures in scalp EEG Clin Neurophysiol. 116(2):427-42, 2005.

Sridevi V, et al.,. Improved Patient-Independent System for Detection of Electrical Onset of Seizures. J Clin Neurophysiol 36:14–24, 2019.

Yidiz I et al., Unsupervised seizure identification on EEG Comput Methods Programs Biomed. 215:106604, 2022.