CURE Epilepsy Discovery: Identification of Environmental Contributors to SUDEP

Key Points:

  • CURE Epilepsy awardee Dr. Franck Kalume and colleagues at the Seattle Children’s Research Institute and New York University sought to identify simple environmental factors that may increase the risk of SUDEP. 
  • The team examined the effects of increased temperature and moderate exercise on several basal involuntary bodily functions of an established mouse model of Dravet syndrome (DS), a severe form of epilepsy with an increased incidence of SUDEP. 
  • When compared to normal mice, DS mice showed diminished regulation of core body temperature as well as cardiac and respiratory function.
  • Understanding the mechanisms behind these impairments might help develop effective approaches to reduce the risk of and perhaps even prevent SUDEP.

Deep Dive:

Sudden unexpected death in epilepsy (SUDEP) is devasting event that occurs in approximately 1 in 1,000 people with epilepsy [1,2]. It appears to be related to seizure-induced dysfunction of the autonomic nervous system (ANS) [3] The ANS controls body functions essential for survival and is responsive to environmental changesSome of these functions include maintenance of core body temperature as well as tight regulation of heart and breathing rates. Previous research has revealed that disruptions in ANS function related to a seizure event are marked by diminished control of these three body processes, but the precise nature and mechanisms of these weakened responses are not clear.

Dr. Franck Kalume, a recipient of CURE Epilepsy’s Sleep and Epilepsy Award, generously funded by the BAND Foundation, explored this important area of research by utilizing his mouse model of Dravet syndrome (DS). [4] DS is a treatment-resistant form of epilepsy with a high risk of SUDEP, and an increased prevalence of ANS dysfunction. This particular mouse model was developed by deleting the gene linked to most cases of DS in humans (known as SCN1A), which is also one of the many genes responsible for propagating electrical signals in the brain.

The first set of experiments involved assessing the ability of DS mice to regulate 1) core body temperature, 2) heart rate, and 3) breathing rate in response to an increase in surrounding temperature, i.e., to 86-90°F. Responses from the DS mice and control mice were subsequently compared [5].  

Before elevating the external temperature, the internal body temperatures of both DS and control mice were similar. In the first 15 min after heat exposure, the core body temperature in both groups increased, although the absolute temperature and rate of this increase was much smaller in DS versus control mice. As exposure to heat was reduced, the core body temperature returned to baseline in control animals, but in DS mice, body temperature remained elevated. These observations suggest that DS mice have deficits in thermoregulation (an ability to control core body temperature).  

Dr. Kalume and his team developed another set of DS mice in which the SCN1A gene had been deleted only in neurons responsible for transmitting inhibitory electrical signals in the brain [5]. The same responses were observed in this second group of DS mice, indicating that thermoregulation is most likely mediated by these inhibitory neurons. 

Along with deficits in controlling core body temperature, the DS mice also had problems regulating cardiac and respiratory function in response to elevated temperature. Specifically, although the heart rate of DS mice increased to only half that of control mice, the rate of recovery was much slower after the heat source had been removed. Likewise, even though the breathing rates decreased in both DS and control mice in response to higher temperatures, it recovered partially in control mice but not at all in DS mice.  

The effect of moderate exercise (running on a treadmill) on heart rate as well as heart rate variability was also assessed [5]. During this exercise challenge, the highest heart rate level reached was much lower in DS than in control mice, and it took much longer for DS mice to reach their peak values. Similar responses were observed for heart rate variability, all of which suggest impaired cardiac function in DS. 

Together, these findings imply that there are clear abnormalities within the ANS of DS mice and, by extension, in people with DS and possibly other intractable epilepsies. Understanding the biological bases of these irregularities and how environmental changes may adversely affect them will likely assist in the development of novel methods to reduce seizure-related health consequences as well as the high risk of SUDEP.   

This work was conducted in collaboration with Dr. Orrin Devinsky of New York University. 

Read more about Dr. Kalume’s research in sleep and epilepsy here

 

 

Literature Cited

  1. Devinsky, O. et al. Sudden unexpected death in epilepsy: epidemiology, mechanisms, and prevention. Lancet Neurol. 2016; 15(10): 1075-1088. 
  2. Devinsky, O. & Sisodiya, S.M. SUDEP: Advances and challenges. Epilepsy Curr. 2020; 20(6 Suppl): 29S-31S. 
  3. Kalume, F. Sudden unexpected death in Dravet syndrome: respiratory & other physiological dysfunctions. Respir. Physiol. Neurobiol. 2013; 189: 324-328. 
  4. Kalume, F. et al. Sudden unexpected death in a mouse model of Dravet syndrome. J. Clin. Invest. 2013; 123: 1798-1808. 
  5. Sahai, N. et al. Disordered autonomic function during exposure to moderate heat or exercise in a mouse model of Dravet syndrome. Neurobiol. Dis. 2021; 147: 105154. 

CURE Epilepsy Discovery: Optimizing Brain Stimulation for People with Drug-Resistant Epilepsy

Key Points:

• Taking Flight grantee Dr. Ankit Khambhati and colleagues at the University of California – San Francisco sought to understand why some people with drug-resistant epilepsy respond better than others to responsive neurostimulation (RNS) therapy.

• After examining the pattern of brain waves of approximately 50 patients, the investigators identified a new biomarker that could predict which people would most benefit from RNS therapy.

• This important finding has the potential to help neurologists decide which patients would benefit the most from an RNS device before it is actually implanted in the brain.

Deep Dive:

Of the millions of people who are impacted by epilepsy, approximately one-third do not respond to currently available antiseizure medications [1], adversely affecting their quality of life. Among those with drug-resistant focal epilepsy (seizures that start from a single area in the brain, formerly known as partial seizures), one of the more effective treatment options involves brain stimulation [2], including the Neuropace Responsive Neurostimulation System® (RNS) [3]. The RNS is a ‘smart’ device implanted on the surface of the brain, with two thin wires placed where the seizures begin. It monitors brain waves recorded from the wires to produce what is called an intracranial electroencephalogram (iEEG). When the RNS device senses abnormal neural activity, it responds with subtle electrical pulses to either terminate or suppress an emerging seizure. The iEEG data can also be mined for research purposes to identify changing patterns in the brain waves as a patient’s condition improves.

The RNS is effective at reducing seizures in many patients with focal epilepsy, but it does not work for every patient, and it is not clear why. Dr. Khambhati and his colleagues, Drs. Edward Chang and Vikram Rao, thought that the lack of response in some people may be related to some seemingly inconsistent observations from numerous clinical trials of the RNS System. As mentioned above, the RNS device was designed to send electrical pulses to terminate a developing seizure only when abnormal electrical activity was detected, but the researchers found actual stimulation often occurred more than 1,000 times a day. This did not correlate with the actual number of seizures reported suggesting a significant amount of abnormal activity between seizures. In addition, clinically significant improvements, i.e., reduction in seizure frequency, occurred gradually over time, often years rather than just immediately after electrical stimulation by RNS [4]. Together, these observations suggested that there is abnormal electrical activity that occurs between seizures, possibly exacerbating them, and that the RNS device both terminates seizures and may also slowly modify how they are generated.

To explore this possibility, Dr. Khambhati and colleagues capitalized on the availability of many years’ worth of iEEG data from approximately 50 patients with an implanted RNS device [5]. Upon close examination of the data, they found a wide range of RNS response effectiveness among these patients and categorized them in three separate groups: super, intermediate, and poor responders based on the percent reduction in seizures.

Comparing the iEEG patterns from each of these groups allowed the researchers to conclude that RNS therapy, in addition to suppressing an emerging seizure, was also inducing a rewiring of the epileptic network, essentially disrupting it. This, in turn, dramatically decreased the brain’s tendency to generate excessive excitatory electrical activity sufficient to trigger a seizure. More importantly, the researchers found that much of this rewiring was a result of stimulation that occurred between seizures rather than just before the “buildup” of electrical activity indicative of seizure onset. Furthermore, since each of the three responder groups exhibited different iEEG “fingerprints”, the researchers were also able to consolidate these data to generate a powerful algorithm that could examine iEEG patterns and pinpoint unique biomarkers reflecting a prospective patient’s likely response to an implanted RNS device.

With this critical advancement, clinical care of patients with focal epilepsy being treated with RNS therapy may be improved beyond the typical adjustment of stimulation parameters. Neurologists may now be able to predict how a patient will respond to RNS, better counsel patients on their prognosis, and adjust stimulation parameters accordingly. Ideally, this discovery will help determine if a patient will even benefit from RNS therapy before the device is even implanted in the brain, thereby reducing unnecessary treatment risks for patients with focal epilepsy.

Literature Cited
1. Chen, Z. et al. Treatment outcomes in patients with newly diagnosed epilepsy treated with established and new antiepileptic drugs: a 30-year longitudinal cohort study. JAMA Neurol. 2018; 75: 279-286.
2. Foutz, T. & Wong, M. Brain stimulation treatments in epilepsy: basic mechanisms and clinical advances. Biomed. J 2021; in press
3. Morrell, M.J. RNS System in Epilepsy Study Group. Responsive cortical stimulation for the treatment of medically intractable partial epilepsy. Neurology 2011; 77: 1295-1304.
4. Nair, D.R. et al. Nine-year prospective efficacy and safety of brain-responsive neurostimulation for focal epilepsy. Neurology 2020; 95: e1244-e1256.
5. Khambhati, A.N. et al. Long-term brain network reorganization predicts responsive neurostimulation outcomes for focal epilepsy. Sci. Transl. Med. 2021; 13(608): eabf6588.

CURE Epilepsy Discovery: Beyond Pharmacological Therapy for the Treatment of Epilepsy: Creating Electrodes to Prevent Seizures by Stimulating the Brain

Dr. Brian Litt at the University of Pennsylvania has dedicated his research career to the creation and improvement of flexible, active, implantable electrodes to monitor and stimulate the brain with the goal of curing epilepsy.

Key Points:

Dr. Brian Litt, MD, Professor in both the Departments of Neurology and Bioengineering at the University of Pennsylvania, obtained a research grant from CURE Epilepsy in 2011 to develop active, flexible, implantable electrodes to treat epilepsy by stimulating the brain.

  • The flexible electrodes are ideal to insert into brain tissue and are able to record brain activity as well as stimulate specific brain areas when a seizure arises, thereby mitigating it.
  • Dr. Litt considers the CURE Epilepsy grant that he received to be pivotal to the development of his laboratory. His laboratory has since grown tremendously and has proven to be a very fertile environment, especially for the training of young researchers who have gone on to work on various research strategies to cure epilepsy.

Deep Dive:

Dr. Litt studied Engineering and Applied Sciences at Harvard University and obtained his medical degree at Johns Hopkins University. When he started treating patients as a neurologist, he realized that the treatments that were available for patients with drug-resistant epilepsy were mostly based on traditional pharmacological interventions and had limited capacity to significantly change the course of the disease. The lack of alternatives for patients who were resistant to pharmacological treatments inspired him to research electrical stimulation as a new method to treat epilepsy, with the goal of preventing seizures to control the disease.

A research grant from CURE Epilepsy in 2011 for “Flexible Implantable Devices for Epilepsy” was instrumental in the development of these technologies, and in defining Dr. Litt’s research trajectory when he started his laboratory at the University of Pennsylvania.

Dr. Litt´s laboratory collaborated with Dr. John Rogers, also at the University of Pennsylvania, who had developed the first flexible electrodes but had not tried implanting them in live tissue at the time. Together, their laboratories developed and tested the first brain implants incorporating active electronics for recording seizure activity and stimulating the brain to control seizures.

Dr. Litt’s research has always been on the forefront of advancing the relationship between medicine and engineering, and he has actively fostered collaborations between these two areas at his university. Dr. Litt belongs to both the Departments of Neurology and Bioengineering and collaborates extensively with research groups with varied areas of expertise and at different institutions all over the country.  

Dr. Litt believes the CURE Epilepsy grant he received many years ago had a great impact on his career. In addition to contributing to epilepsy research in an essential way, it has enabled him to train the next generation of epilepsy researchers. Over the years, he has trained over 50 PhD students and post-doctoral researchers with the majority of them still successfully working on epilepsy today. Several of his trainees have started their independent research careers in epilepsy and secured NIH funding for their projects. 

Dr. Litt wants donors to know how important CURE Epilepsy has been to his successful career.  “I can’t tell you how grateful I am to the organization and the donors. […] Probably the biggest impact of CURE Epilepsy is that the organization doesn’t spend dollars foolishly. You carefully bet on the people as well as the projects. You’re very good stewards of the money.” Additionally, he commented, “Research is incremental. It builds on itself with time. Getting the result of the research is just one piece of the puzzle, but what’s even more important is getting a lot of smart young people to think about epilepsy and work on it, so you build this critical mass and this community.”  

The CURE Epilepsy grant allowed Dr. Litt to start his research to develop implantable electrodes to stimulate the brain. Considering the limitations of pharmacological therapy for many epilepsy patients, it is essential to increase the range of available treatments, and the work from Dr. Litt’s laboratory makes a cure for epilepsy closer to becoming a reality. Dr. Litt and his group members, past and present, are at the frontline of this fascinating and fundamental endeavor, and CURE Epilepsy is a proud supporter of this enterprise. 

 # # # 

A special thank you to Irene Sanchez Brualla, PhD, for her assistance with this article. 

2021 Curing the Epilepsies Conference: The Epilepsy Community at an Inflection Point

Key Points:

  • The 2021 Curing the Epilepsies conference assembled diverse stakeholders from the epilepsy community to discuss the status of epilepsy research and transformative research priorities.
  • During the 2021 conference, participants identified several key topics as indispensable for advancing epilepsy research and improving the lives of those impacted by epilepsy, including integrating epilepsy care and research, improving measurement and tracking of health outcomes, and reducing health disparities for underserved communities.
  • In an editorial published after the conference, members of the epilepsy advocacy community, co-led by CURE Epilepsy’s Chief Scientific Officer Dr. Laura Lubbers, proposed development of a National Plan to address the epilepsies. This plan would include a comprehensive strategy, the infrastructure, and the expanded partnerships to rapidly translate scientific discoveries into better health outcomes for people with epilepsy.

Deep Dive:  

The Curing the Epilepsies conference has been held approximately every seven years since the first one in 2000.  The initial conference was established with the help of CURE Epilepsy, with governmental funding agencies, professional societies, and other patient advocates also contributing.  As in the past, the 2021 conference included stakeholders such as clinicians, researchers, and especially patients and caregivers, to review scientific discoveries and transformative research priorities with the ultimate goals of 1) curing epilepsy with no side effects and 2) preventing epilepsy in people at risk. Research progress, documented in an editorial recently published in the journal Epilepsy Currents [1], has led to an enhanced understanding of: 

  •  epileptogenesis, the processes by which epilepsy develops  
  • increased risk of premature death, especially from sudden unexpected death in epilepsy (SUDEP)  
  • epilepsy-associated comorbidities such as depression 
  • technologically based diagnostics, especially in neuroimaging and genetic testing  
  • non-pharmacological treatment options, particularly for surgery and implantable devices for treating seizures [1].  

It was also recognized that despite such compelling scientific strides, these exciting developments have yet to significantly improve health outcomes for people with epilepsy.  

To truly accelerate progress and cure the epilepsies, leaders in the epilepsy advocacy community propose development of a comprehensive research strategy as part of a National Plan [2] to address the epilepsies. A National Plan would bring together the necessary infrastructure and expanded partnerships needed to rapidly translate scientific discoveries into better health outcomes. A key goal of the plan would include improving patient care and the quality of patient-centered data, both key to catalyzing the following four transformative priorities:  

1) consolidation of research and clinical care  

2) lessening of health disparities faced by underserved populations 

3) consistent monitoring of patient outcomes  

4) creation of a nationwide database with statistics on epilepsy burden, prevalence, incidence, epidemiology, and mortality categorized according to distinct criteria such as age, race, ethnicity, and socioeconomic status.   

Carrying out the National Plan will require the combined efforts of many stakeholder groups, including researchers, clinicians, advocacy groups, and, most importantly, people with epilepsy and their families. It is crucial that the courageous voices of patients and their families and their lived experiences, are incorporated into all steps of the research planning process. Working together, we can chart the course for aligning the infrastructure, incentives, research needs, and resources to put the nation on a path toward curing the epilepsies.? 


Literature Cited 

  1. Marsh, E.D. et al. The 2021 Epilepsy Research Benchmarks – respecting core principles, reflecting evolving community priorities. Epilepsy Currents 2021; Epub – Online first 
  1. Miller, I.P. et al. Epilepsy community at an inflection point: translating research toward curing the epilepsies and improving patient outcomes. Epilepsy Currents 2021; Epub – Online first 

CURE Epilepsy Discovery: Heart Dysfunction Is a Risk Factor for SUDEP

Key Points:

  • CURE Epilepsy Award grantee Dr. Christopher Reid and his team sought to understand the genetic connection between sudden expected death in epilepsy (SUDEP) and cardiac arrhythmia with the goal of improving treatment for people with epilepsy and reducing the risk of SUDEP.
  • The team focused on KCNH2, a gene whose loss-of-function mutations are linked to cardiac arrhythmias and increased SUDEP risk in humans.
  • Currently, the team is generating laboratory models with genetic mutations comparable to those found in humans, to explore the link between cardiac abnormalities and SUDEP risk with greater precision than is feasible with humans.

Deep Dive:

SUDEP is the most common cause of death among people with treatment-resistant epilepsy [1], but its underlying biological cause remains obscure. There is strong evidence of the association of breathing problems with SUDEP [2,3], but there is also equally strong, if not more so, data for cardiac abnormalities, particularly cardiac arrhythmias (irregular heartbeat). In fact, studies have found mutations in genes associated with cardiac arrhythmias in SUDEP patients [4].

Dr. Christopher Reid and his team at the Florey Institute of Neuroscience & Mental Health at the University of Melbourne sought to build upon the known relationship between cardiac abnormalities and SUDEP risk by identifying specific genes involved in proper cardiac function. With the assistance of a CURE Epilepsy Award, they chose to focus on a gene known as KCNH2, which affects the spread of electrical signals in the heart. KCNH2 variants that result in a loss of cardiac function are a well-known cause of long QT syndrome [5], a potentially fatal condition that affects heart function and which has as a distinct pattern on an electrocardiogram.

 Prior research revealed that KCNH2 was one of thirty genes found in an analysis of rare genetic variants in SUDEP patients when compared to controls [6]. Following up on that work and as part of this study, the team characterized the variants, finding that about 8% of SUDEP cases carry a KCNH2 variant that causes the gene to not function (7). As a result of these findings, the team proposed that the risk of SUDEP is significantly higher for a person who experiences seizures and carries a KCNH2 loss-of-function variant than for a person who has seizures but does not carry a loss-of-function variant. This suggests that the presence of loss-of-function mutations of KCNH2 may serve as valuable biomarkers for SUDEP risk [7].

To probe this relationship with greater precision than is possible in humans, Dr. Reid and his team are currently generating laboratory models with mutations in genes that are involved in cardiac arrhythmias and development of epilepsy, comparing their SUDEP risk to those models with either arrhythmia alone or epilepsy alone. Based on the human studies, the expectation is that the combination of cardiac- and epilepsy-related genetic mutations will result in a much greater propensity for sudden death. The eventual goal is to use these data to help understand how cardiac function and epilepsy might intersect and inform clinical guidelines for the treatment of epilepsy patients, hopefully reducing SUDEP risk in the process.

Literature Cited

  1. Thurman, D.J. et al. The burden of premature mortality of epilepsy in high-income countries: a systematic review from the Mortality Task Force of the International League against Epilepsy. Seizure 2017; 58(1): 17-26.
  2. Ryvlin, P. et al. Incidence and mechanisms of cardiorespiratory arrests in epilepsy monitoring units (MORTEMUS): a retrospective study. Lancet Neurol. 2013; 12(10): 966-977.
  3. Wenker, I.C. et al. Postictal death is associated with tonic phase apnea in a mouse model of sudden expected death in epilepsy. Neurol. 2021; 89: 1023-1035.
  4. Bagnall, R.D., Crompton, D.E., and Semsarian, C. Genetic basis of sudden unexpected death in epilepsy. Neurol. 2017; 8: 348.
  5. Bleakley, L.E. et al. Are variants causing cardiac arrhythmia risk factors in sudden unexpected death in epilepsy? Neurol. 2020; 11: 925.
  6. Bagnall, R.D. et al. Exome-based analysis of cardiac arrhythmia, respiratory control, and epilepsy genes in sudden unexpected death in epilepsy. Neurol. 2016; 79(4): 522-534.
  7. Soh, M.S. et al. Loss-of-function variants in Kv11.1 cardiac channels as a biomarker for SUDEP. Clin. Transl. Neurol. 2021; Epub ahead of print.

CURE Epilepsy Discovery: When Does a Seizure Lead to SUDEP?

Key Points:

  • CURE Epilepsy Taking Flight grantee Dr. Ian Wenker and colleagues used mouse models to determine the series of biological events underlying sudden expected death from epilepsy (SUDEP).
  • Analysis of electrical activity from the brain and heart, along with breathing, revealed that the main cause of death was apnea (breathing cessation), which originated during the tonic phase of a seizure, the stage during which muscles stiffen.
  • Restoration of breathing, either naturally or artificially, soon after the seizure had ended increased the rate of survival, thereby preventing SUDEP.
  • The clinical relevance of these data was reflected in an epilepsy patient whose breathing disruptions were similar to those observed in the mice.

Deep Dive:

SUDEP is a devastating outcome for some people with epilepsy, and the most common cause of death among people with treatment-resistant epilepsy [1]. Despite significant research into the cause of SUDEP [2], including an implication of cardiorespiratory dysfunction [1,3], the precise series of biological events ultimately leading to death is not clear.

With the help of a CURE Epilepsy Taking Flight award, Dr. Ian Wenker and colleagues, working in the laboratory of Dr. Manoj Patel at the University of Virginia School of Medicine, sought to better understand these events. Specifically, they sought to determine the order in which physiological processes occur, the circumstances that lead to death, and what could be done during the seizure to prevent death [4]. The researchers used mouse models of epilepsy wherein seizures were induced either genetically or chemically. They measured breathing and monitored electrical activity from the brain and heart for both fatal and nonfatal seizures.

Dr. Wenker and colleagues found that during the tonic phase of a seizure, the phase in which muscles, including the primary breathing muscle known as the diaphragm, become rigid, breathing disruptions (apnea) were common. However, death only occurred if breathing did not promptly restart after the seizure. This conclusion was then tested by mechanically ventilating those mice whose breathing had not fully recovered after the seizure, and they survived.

To extend these exciting findings from mice to people with epilepsy, the researchers examined the corresponding data from a patient with a harmful genetic mutation similar to that in the mutant mice. The breathing patterns, frequency, and disruptions in this individual were comparable to those from seizure-susceptible mice, suggesting that treating any breathing disruptions in patients post-seizure may prevent SUDEP. Dr. Wenker plans to build on these data and hopes to contribute to the development of a protocol that may one day eliminate SUDEP completely.

Literature Cited

  1. Ryvlin, P. et al. Incidence and mechanisms of cardiorespiratory arrests in epilepsy monitoring units (MORTEMUS): a retrospective study. Lancet Neurol. 2013; 12(10): 966-977.
  2. Jones, L.A. & Thomas, R.H. Sudden death in epilepsy: Insights from the last 25 years. Seizure 2017; 44: 232-236.
  3. Stewart, M. et al. Causes and effects contributing to sudden death in epilepsy and the rationale for prevention and intervention. Neurol. 2020; 11: 765.
  4. Wenker, I.C. et al. Postictal death is associated with tonic phase apnea in a mouse model of sudden expected death in epilepsy. Neurol. 2021; 89: 1023-1035.
a red pencil draws the outline of a human head over a graphic of neurons

CURE Epilepsy’s Impact: Investing in Early-Stage Research Leads to Critical Advancements

Key Points:

  • Nearly 20 years ago, Peter Carlen, MD received a one-year grant from CURE Epilepsy that served as a catalyst for his research into seizure detection and electrical neurostimulation. One of the companies Dr. Carlen established continues the work in seizure detection and is currently building on his lab’s recent identification of a biomarker for sudden unexpected death in epilepsy (SUDEP).
  • For more than 20 years, through investing in paradigm-shifting ideas, CURE Epilepsy has enabled scientists to discover insights essential for advancing the understanding of epilepsy and moving us closer to a cure.

Deep Dive:

Dr. Carlen began his career as a general neurologist at the University of Toronto. He founded the Epilepsy Program at the Toronto Western Hospital 25 years ago and is now one of its staff epileptologists. With his 2002 funding from CURE Epilepsy, he collaborated with mathematician and engineer Dr. Berj Bardakjian and a student with a background in physics, Dr. Houman Khosravani, to investigate the promise of computation and engineering techniques to understand epileptic networks and to ultimately develop the ability to disrupt them.

The work facilitated by his CURE Epilepsy-funded grant has contributed substantially to prediction and treatment of epilepsy. The researchers first published a paper documenting arrest of seizure activity with brief, low frequency electrical pulses delivered to brain tissue [1] and later published two additional papers on electrical neurostimulation [2,3]. Since these initial studies, Carlen’s lab has progressed to more advanced testing paradigms with modified parameters to make the pulses more akin to what actually happens in the brain. Significantly, this newer protocol appears to result in better seizure control than the more traditional pattern of repetitive square pulses.

Perhaps some of the most frightening and challenging aspects of epilepsy are seizure unpredictability and the potential for SUDEP; thus, seizure and SUDEP forecasting remain priorities in epilepsy research. Dr. Carlen’s current research also focuses on the brainstem, a small area at the base of the brain located just above the spinal cord, that regulates functions such as breathing and heart rate. Hypothesizing that SUDEP reflects disturbances in the brainstem, Carlen’s lab measured the electrical activity from this brain region in rats and discovered that seizures originating here led to cardiorespiratory arrest and death [4,5], important findings that continue to influence the field.

Since the initial research supported by their 2002 CURE Epilepsy grant, Carlen and Bardakjian have continued to collaborate, recently making a breakthrough that could reduce overall morbidity and mortality in epilepsy: they have developed a seizure alarm and identified SUDEP biomarkers in the unique electrical patterns of the electroencephalogram (EEG) [6]. They have since founded a company called Neurometrics Technologies to develop this technology further, with the goal of combining a wireless headset with complex computer algorithms capable of analyzing a patient’s EEG patterns to predict seizures and detect SUDEP biomarkers.

Carlen finds serving as the bridge between his patients in the clinic and the basic research in his lab especially rewarding. As an epileptologist, he witnesses firsthand the intense suffering endured by people with epilepsy and, as a scientist, he is in a unique position to develop more effective treatments with little to no side effects, a true cure.

CURE Epilepsy is proud to have played a role in advancing research by Dr. Peter Carlen and his colleagues, building hope for prevention and cures, and ultimately, a world without epilepsy.


Literature Cited
[1] Khosravani, H., Carlen, P.L., & Velazquez, J.L.P. The control of seizure-like activity in the rat hippocampal slice. Biophys. J. 2003; 84: 687-695.
[2] Chiu, A.W.L., Jahromi, S.S., Khosravani, H., Carlen, P.L. & Bardakjian, B.L. The effects of high-frequency oscillations in hippocampal electrical activities on the classification of epileptiform events using artificial neural networks. J. Neural Eng. 2005; 3(1): 9-20.
[3] Khosravani, H., Pinnegar, C.R., Mitchell, J.R., Bardakjian, B.L., Federico, P., & Carlen, P.L. Increased high-frequency oscillations precede in vitro low-Mg2+ seizures. Epilepsia 2005; 46(8): 1188-1197.
[4] Salam, M.T., Montandon, G., Genov, R, Devinsky, O., Del Campo, M., & Carlen, P.L. Mortality with brainstem seizures from focal 4-aminopyridine-induced hippocampal seizures. Epilepsia 2017; 58(9): 1637-1644.
[5] Lertwittayanon, W., Devinsky, O., & Carlen, P.L. Cardiorespiratory depression from brainstem seizure activity in freely moving rats. Neurobiol. Dis. 2020; 134: 104628.
[6] Grigorovsky, V. et al. Delta-gamma phase-amplitude coupling as a biomarker of postictal generalized EEG suppression. Brain Commun. 2020; 2(2): fcaa182.

CURE Epilepsy Discovery: A Novel Molecule as a Biomarker of Epilepsy

Key Points:

  • CURE Epilepsy Taking Flight Award grantee Dr. Gary Brennan and colleagues used three different, well-established rodent models of acquired epilepsy to identify biomarkers for both diagnosing active epilepsy and for predicting who might develop epilepsy after a brain injury.
  • The team found that a family of small molecules known as microRNAs (miRNAs)[1], which are important in regulating gene expression and brain activity, were altered in rodent models of acquired epilepsy.
  • Three of the five identified miRNAs were also present in blood samples taken from epilepsy patients, thereby validating their relevance to human epilepsy.
  • Administration of a molecule known as Ant-134, which has been previously shown to reduce seizure frequency in different animal models, affected the levels of three of the five miRNAs in rodent models of acquired epilepsy in the current study.
  • These preliminary data suggest that circulating miRNAs may represent biomarkers that can accurately diagnose epilepsy and predict who may develop it after a brain injury. Additional steps to validate these miRNAs as biomarkers of acquired epilepsy are needed.

Deep Dive:

Epilepsy is often “acquired” by injuries to the brain such as those resulting from a stroke, head trauma, or infection. There is currently no way of reliably predicting who will develop epilepsy following these types of injuries [2]. Thus, it would be valuable to have a stable, readily accessible substance (in the blood, for example) to assist with diagnosis, treatment, and epilepsy prediction following a head injury for people at risk. MicroRNAs (miRNAs), small molecules that have been implicated in the development of epilepsy [3], may make ideal biomarkers due to their relatively high concentrations in the blood. CURE Epilepsy Taking Flight Award grantee Dr. Brennan investigated whether miRNAs might be used as biomarkers of acquired epilepsy.

Dr. Brennan and his colleagues employed three different rodent models of acquired epilepsy to evaluate the feasibility of using miRNAs as biomarkers for the development of epilepsy [4]. The researchers first collected blood from all rodents to establish baseline levels of the different miRNAs. They subsequently sampled blood several times prior to the first seizure and also on the day of the first spontaneous seizure, which was indicative of the actual onset of epilepsy.

The researchers found that blood from rodents with epilepsy had several unique miRNAs, either newly-emerged or whose levels had changed during epileptogenesis –the process by which an initial “insult” or injury to the brain leads to seizures and epilepsy–and into the chronic epilepsy stage. Based on consistency among the three rodent models and previous associations with epilepsy, the researchers chose five of these miRNAs as a focus for the next steps of their work. Importantly, they found that three of the five miRNAs were also found in people with epilepsy.

Dr. Brennan also found that levels of three of the five miRNAs were affected by a potential new therapy for epilepsy called Ant-134. Anti-134 is a molecule that specifically targets a different miRNA (miRNA-134), distinct from the five miRNAs that were the focus of Dr. Brennan’s study. Anti-134 has been shown to reduce seizures in several different rodent models of epilepsy [5]. Dr. Brennan’s finding supports the idea that specific miRNAs may be useful for predicting the likelihood of developing an acquired epilepsy as well as potential indicators of treatment responsiveness.

These exciting data reveal a novel mechanism of epilepsy prediction, diagnosis, and treatment that may one day be studied in clinical trials to determine its ability to identify individuals who have suffered a brain injury that are likely to develop epilepsy.


Dr. Gary Brennan

Dr. Brennan performed his work while in the laboratory of Dr. David Henshall at the Royal College of Surgeons in Ireland. He collaborated with multiple colleagues, both in Dr. Henshall’s lab and from specialist labs across Europe.

Dr. Brennan has received additional support from the Science Foundation Ireland and is a funded investigator in the FutureNeuro Research Centre. His research group is based in the School of Biomolecular and Biomedical Science at University College Dublin.

 


Literature Cited
[1] miRNA are (a relatively newly discovered form of ribonucleic acid (RNA) and) distinct from other forms of ribonucleic acids (RNA) like mRNA or tRNA that serve different biological functions.
[2] Löscher, W. The holy grail of epilepsy prevention: preclinical approaches to antiepileptogenic treatments. Neuropharmacology 2020; 167: 107605.
[3] Henshall, D.C. et al. MicroRNAs in epilepsy: pathophysiology and clinical utility. Lancet Neurol. 2016; 15(3): 1368-1376.
[4] Brennan, G.P. et al. Genome-wide microRNA profiling of plasma from three different animal models identifies biomarkers of temporal lobe epilepsy. Neurobiol. Dis. 2020; 144: 105048.
[5] Morris, G., Reschke, C.R., and Henshall, D.C. Targeting microRNA-134 for seizure control and disease modification in epilepsy. EbioMedicine 2019; 45: 646-654.

Understanding the Neurodevelopmental Origins of Focal Cortical Dysplasia (FCD)

Key Points:

  • CURE Epilepsy Taking Flight Award grantee Dr. Lakshmi Subramanian is working to uncover the underlying causes of focal cortical dysplasia (FCD), a severe childhood epilepsy syndrome characterized by developmental malformations in the part of the brain known as the cortex.
  • Dr. Subramanian found that disrupting the mTOR signaling pathway caused a series of biological changes that may explain how FCD arises.
  • Understanding these changes could help researchers identify newer, more effective, and less invasive therapeutic options than those currently available.

Deep Dive:

During development in the womb, the human brain undergoes a substantial expansion in size, particularly in the outermost part known as the cortex [1]. During this time, brain cells grow and divide rapidly, normally organizing themselves into layers. As the brain develops, an orderly arrangement of cells is created, in part, by the shape, position, and movement of outer radial glia (oRG) cells. These cells give rise to newborn nerve cells in the human brain and also form the scaffold that the immature nerve cells use to navigate to their correct location, mature, and connect normally [3]. In focal cortical dysplasia (FCD), however, brain cells fail to organize properly, leading to focal lesions and usually intractable epilepsy [2]. Surgery is often the only effective treatment option.

The mTOR pathway is known to be active in human oRG cells during development [4], but the function of this pathway in these cells is unknown. Taking Flight Award grantee Dr. Lakshmi Subramanian, while working in the laboratory of Dr. Arnold Kriegstein at University of California San Francisco, sought to determine the specific role of the mTOR pathway in the development of FCD [5].

Dr. Subramanian and colleagues first successfully established simplified models of the developing human cortex in order to manipulate mTOR signals and evaluate the resulting effects on oRG cells. They activated or blocked mTOR signals in two different human tissue-based models and found that sustained mTOR signals were required to maintain oRG cell shape and structure. Specifically, when mTOR signals were disrupted, oRG cells lost their typically elongated shape, shortened significantly, and lost their ability to “move” normally in the developing brain. As a result, the scaffold along which nerve cells migrate, mature, and connect was also disrupted, providing a mechanism for how abnormal brain organization may arise in FCD.

In future research, Dr. Subramanian hopes these human brain model systems can be used to investigate how displaced, misshapen oRG cells affect long-term changes in the brain. More information about how oRG cells use mTOR signals may help identify additional components of the pathway that can be investigated as potential therapies or diagnostics. An advanced understanding of this pathway may allow for development of less invasive approaches to treating FCD and other mTOR-mediated developmental epilepsies. These proteins could conceivably be targeted to develop new diagnostics and treatments other than invasive surgery for patients with FCD and other mTOR-mediated developmental epilepsies.


Dr. Lakshmi Subramanian

Dr. Lakshmi Subramanian is a CURE Epilepsy Taking Flight Award grantee and NARSAD Young Investigator, Neuroscience/Stem Cell Biology Research at Broad Center for Regeneration Medicine, University of California San Francisco.

 


Literature Cited
[1] Hatten, M.E. Central nervous system neuronal migration. Annu. Rev. Neurosci. 1999; 22: 511-539.
[2] Iffland, P.H. and Crino, P.B. Focal cortical dysplasia: gene mutations, cell signaling, and therapeutic implications. Annu. Rev. Pathol. 2017; 12: 547-571.
[3] Ostrem, B., Di Lullo, E., and Kriegstein, A.R. oRGs and mitotic somal translocation – a role in development and disease. Curr. Opin. Neurobiol. 2017; 42: 61-67.
[4] Pollen, A.A., Bhaduri, A., Andrews, M. et al. Establishing cerebral organoids as models of human-specific brain evolution. Cell 2019; 176(4): 743-756.
[5] Andrews, M.G., Subramanian, K., and Kriegstein, A.R. mTOR signaling regulates the morphology and migration of outer radial glia in developing human cortex. eLife 2020; 9: e58737.

Screening of Genetically Diverse Mice Identifies Novel Rodent Models of Diverse Epilepsy Outcomes

Funded by the generosity of families who have experienced a loss due to SUDEP.

Key Points:

  • CURE Epilepsy Taking Flight Award grantee Dr. Bin Gu and colleagues used genetically diverse mouse strains to identify those that vary in seizure susceptibility, seizure spread, seizure development, and sudden unexpected death in epilepsy (SUDEP).
  • Initial screening of these mice identified four different genetic strains that suddenly and unpredictably died after inducing a single seizure, suggesting these mice may represent novel models for studying SUDEP.
  • Further genetic characterization of these four mouse strains should provide valuable insights into the underlying genetic risk factors for SUDEP.

Deep Dive:

Dr. Bin Gu, PhD

Dr. Bin Gu, PhD

SUDEP is the sudden, unexpected death of someone with epilepsy who otherwise appears healthy. To facilitate an understanding of the complex genetic basis of SUDEP, studies need to use genetically diverse mouse populations [1,2], such as the “Collaborative Cross” [3,4], which can help identify different genetic risk factors that control SUDEP susceptibility.

With the help of a CURE Epilepsy Taking Flight Award, Dr. Bin Gu and his colleagues in the laboratories of Drs. Ben Philpot and Fernando Pardo-Manuel de Villena at the University of North Carolina at Chapel Hill used Collaborative Cross mice to identify mouse strains that were more likely to have seizures, were more prone to having subsequent seizures, were more susceptible to having their seizures spread throughout the brain and were especially vulnerable to SUDEP [5].

The researchers screened mice from this population to identify candidate genes and genetic variants linked to many key symptoms of epilepsy. For example, within this population of mice, when Dr. Gu induced epilepsy, he observed that some mouse strains were resistant to developing epilepsy, whereas others were more susceptible. Identifying the genetics of the resistant strains is important for understanding the mechanisms underlying seizures and developing new ways of stopping seizures before full-blown epilepsy develops.

Among the groups of mice that Dr. Gu studied, four strains of mice died suddenly after a single seizure that was not fatal in “normal” mice. Although the precise cause of sudden death in these mice is currently unknown, the specific strains may eventually provide important clues to the causes of SUDEP in humans.

Dr. Gu’s upcoming research will focus on characterizing these “pro-SUDEP” strains, identifying those genes that control SUDEP susceptibility and resistance and studying the biological causes, including cardiac and respiratory events, that can provoke SUDEP. Such an understanding will hopefully lead to effective strategies to prevent SUDEP.

By providing Dr. Gu with critical initial funding for his research through a Taking Flight Award, CURE Epilepsy has also helped advance Dr. Gu’s career. He will soon establish his own independent lab as an Assistant Professor of Neuroscience at Ohio State University, where he will continue to pursue his passion for epilepsy research.

Dr. Bin Gu is a postdoctoral fellow at the University of North Carolina at Chapel Hill.


Literature Cited
[1] Saul, M.C. et al. High-diversity mouse populations for complex traits. Trends Genet. 2019; 35(7): 501-514.
[2] Bogue, M.A. et al Collaborative cross and diversity outbred data resources in the mouse phenome database. Mamm. Genome 2015; 26(9-10): 511-520.
[3] Churchill, G.A. et al. Complex Trait Consortium. The collaborative cross, a community resource for the genetic analysis of complex traits. Nature Genetics 2004; 36(11): 1133-1137.
[4] Srivastava, A. et al. Genomes of the mouse collaborative cross. Genetics 2017; 206(2): 537-556.
[5] Gu, B. et al. Collaborative cross mice reveal extreme epilepsy phenotypes and genetic loci for seizure susceptibility. Epilepsia 2020; 61(9): 2010-2021.