Susceptibility to Epilepsy After Traumatic Brain Injury is Associated with Preexistent Gut Microbiome Profile

Abstract found in Wiley Online Library


Objective: We examined whether post-traumatic epilepsy (PTE) is associated with measurable perturbations in gut microbiome.

Methods: Adult Sprague-Dawley rats were subjected to Lateral Fluid Percussion Injury (LFPI). PTE was examined 7 months after LFPI, during a 4-week continuous video-EEG monitoring. 16S ribosomal ribonucleic acid gene sequencing was performed in fecal samples collected before LFPI/sham-LFPI and 1 week, 1 and 7 months thereafter. Longitudinal analyses of alpha diversity, beta diversity, and differential microbial abundance were performed. Short-chain fatty acids (SCFA) were measured in fecal samples collected before LFPI by Liquid Chromatography with Tandem Mass Spectrometry.

Results: Alpha diversity changed over time in both LFPI and sham-LFPI subjects; no association was observed between alpha diversity and LFPI, the severity of post-LFPI neuromotor impairments, and PTE. LFPI produced significant changes in beta diversity and selective changes in microbial abundances associated with the severity of neuromotor impairments. No association between LFPI-dependent microbial perturbations and PTE was detected. PTE was associated with beta diversity irrespective of timepoint vis-à-vis LFPI, including at baseline. Preexistent fecal microbial abundances of four amplicon sequence variants belonging to the Lachnospiraceae family (three enriched and one depleted) predicted the risk of PTE with area under the curve (AUC) of 0.73. Global SCFA content was associated with the increased risk of PTE with AUC of 0.722, and with 2-Methylbutyric (depleted), valeric (depleted), isobutyric (enriched) and isovaleric (enriched) acids being most important factors (AUC of 0.717). When the analyses of baseline microbial and SCFA compositions were combined, AUC to predict PTE increased to 0.78.

Significance: While lateral fluid percussion injury produces no perturbations in the gut microbiome that are associated with PTE, the risk of PTE can be stratified based on preexistent microbial abundances and short-chain fatty acid content.

Researchers Create Breakthrough Model For Helping Patients With Post-Traumatic Epilepsy

Article published in Texas A&M Today

TBI is among the leading causes of injury-related death and disability in the United States, with an estimated 5 million people living with the challenges of a long-term TBI-related disability. With symptoms ranging from “mild” to “severe,” individuals who suffer from TBIs can develop a wide range of long-term consequences such as poor motor balance, depression, post-traumatic stress disorder (PTSD), dementia, epilepsy and premature death.

Spontaneous recurrent seizures (SRS) may occur in the months or years following the injury, which is commonly referred to as post-traumatic epilepsy (PTE). Currently, there is no effective treatment or cure for PTE; therefore, there is a critical need to develop animal models to help further understand and assess the mechanisms and interventions related to TBI-induced epilepsy.

  1. Samba Reddy, a professor in the Department of Neuroscience and Experimental Therapeutics at the Texas A&M University College of Medicine, and his team have created a novel experimental model that is able to successfully replicate the same spontaneous recurrent seizures that occur in humans who develop TBI-induced epilepsy. Their findings were recently published in the journal Experimental Neurology. This research, funded by grants from the Department of Defense, can be used to test medical treatments to prevent seizures and other neuropsychiatric conditions in military personnel.

This is a game-changing model on many fronts, Reddy said.

In addition to long-term EEG analysis, Reddy’s team profiled a longitudinal change in the brain in two other major areas: brain tissue histology and behavioral patterns. Behaviorally, the test subjects showed sensory and behavioral functional deficits as well as long-term memory dysfunction — too often overlooked facets of the condition in humans that can negatively affect the quality of life and independent functioning.

In neuropathology analysis, the researchers’ findings showed degeneration of principal neurons and a loss of inhibitory interneurons in the brain. Interneurons normally function as a brake to slow electrical activity, so loss of these special neurons causes excess electrical activity in the brain. There was also an increased incidence of mossy fiber sprouting, which is a hallmark cellular change found in temporal lobe epilepsy.

Early Posttraumatic Seizures Linked to Poor Outcomes in Moderate to Severe TBI Patients

Article published in Healio

Early posttraumatic seizures following moderate to severe TBI were linked to poorer in-hospital and long-term outcomes, including posttraumatic epilepsy, according to an Australian registry-based cohort study published in JAMA Neurology.

“The role of [early posttraumatic seizures (EPS)] in the subsequent development of recurrent unprovoked seizures, or posttraumatic epilepsy (PTE), is not well understood,” Joshua Laing, BBiomedSc, MBBS, of the department of neurosciences at Monash University, and colleagues wrote. “Early posttraumatic seizures may increase the risk of PTE. Whether treatment of EPS exerts an antiepileptogenic effect on developing PTE is largely unknown.”

Researchers evaluated risk factors for EPS and contribution to PTE, as well as associated morbidity and mortality, by collecting data from an Australian-based cohort of 15,152 adults (69% male, median age 60 years) diagnosed with moderate to severe TBI between January 2005 and December 2019, along with a 2-year follow-up.

After adjusting for confounders, researchers associated EPS with increased ICU admission and length of stay, ventilation and duration, length of hospital stay and discharge to rehabilitation facilities instead of home, but not in-hospital mortality. Outcomes in TBI admission survivors at the 2-year follow-up included mortality (RR=2.14; 95% CI, 1.32-3.46), development of PTE (RR=2.91; 95% CI, 2.22-3.81) and use of antiseizure medications (RR=2.44; 95% CI, 1.98-3.02), which were poorer for cases with EPS after adjustment for confounders.

“In this study of moderate to severe TBI inclusive of all seizures during the acute admission, just 11% of patients with EPS developed PTE, although this was significantly greater that the 3% incidence in those without EPS,” Laing and colleagues wrote.

In a related editorial, CURE Epilepsy Grantee James J. Gugger, MD, PharmD, and Ramon Diaz-Arrastia, MD, PhD, from the department of neurology at University of Pennsylvania Perelman School of Medicine, noted that while Laing and colleagues’ findings were significant, statistics may be even more alarming for PTE development following EPS.

Brivaracetam (Briviact®) Prevents the Development of Epileptiform Activity When Administered Early After Cortical Neurotrauma in Rats

Abstract, originally published in Epilepsia

Objectives: There is no effective therapy to prevent the development of posttraumatic epilepsy (PTE). Recently, we reported that administration of the antiseizure medication (ASM) levetiracetam (LEV) shortly after trauma prevented the development of epileptiform activity in two experimental models of neurotrauma. However, the time window for effective intervention with LEV may be too narrow for most clinical settings. Using the controlled cortical impact (CCI) injury model, the current study tested whether early administration of brivaracetam (BRV), an ASM with 20 times the affinity of LEV for the SV2A synaptic vesicle protein, could improve upon the antiepileptogenic action observed with LEV.

Methods: Rats (postnatal day [P] 24–32) subjected to CCI injury were given a single dose of BRV (21 or 100 mg/kg, i.p.) at one of three post-injury time points: immediately (0–2 minutes), 30 minutes, or 60 minutes. Control animals received only vehicle (0.9% saline). Posttraumatic electrographic epileptiform activity was assayed ex vivo from coronal neocortical slices collected proximal to the injury (four per rat) 3–4 weeks after injury. In this model, ictal-like burst discharges occur spontaneously or can be evoked in an “all or none” manner with applied electrical stimulation within the first 2 weeks after injury.

Results: A single dose of BRV administered to rats up to 60 minutes after traumatic brain injury (TBI) significantly reduced the development of posttraumatic epileptiform activity by (1) inhibiting the development of both evoked and spontaneous epileptiform activity, (2) raising the threshold for stimulus-evoked epileptiform discharges, and (3) reducing the intensity of epileptiform bursts that arise after cortical neurotrauma.

Significance: Clinically there has been little success preventing the development of posttraumatic epilepsy. The results of this study support the hypothesis that early intervention with briveracetam has the potential to prevent or reduce posttraumatic epileptogenesis, and that there may be a limited time window for successful prophylactic intervention.

Blocking Receptor for Advanced Glycation End Products (RAGE) or Toll-Like Receptor 4 (TLR4) Prevents Post-Traumatic Epileptogenesis in Mice

Featuring the work of CURE Epilepsy grantee Dr. Xiaoming Jin

Abstract, originally published in Epilepsia

Objective: Effective treatment for the prevention of posttraumatic epilepsy is still not available. Here, we sought to determine whether blocking receptor for advanced glycation end products (RAGE) or toll-like receptor 4 (TLR4) signaling pathways would prevent posttraumatic epileptogenesis.

Methods: In a mouse undercut model of posttraumatic epilepsy, daily injections of saline, RAGE monoclonal antibody (mAb), or TAK242, a TLR4 inhibitor, were made for 1 week. Their effects on seizure susceptibility and spontaneous epileptic seizures were evaluated with a pentylenetetrazol (PTZ) test in 2 weeks and with continuous video and wireless electroencephalography (EEG) monitoring between 2 and 6 weeks after injury, respectively. Seizure susceptibility after undercut in RAGE knockout mice was also evaluated with the PTZ test. The lesioned cortex was analyzed with immunohistology.

Results: Undercut animals treated with RAGE mAb or TAK242 showed significantly higher seizure threshold than saline-treated undercut mice. Consistently, undercut injury in RAGE knockout mice did not cause a reduction in seizure threshold in the PTZ test. EEG and video recordings revealed a significant decrease in the cumulative spontaneous seizure events in the RAGE mAb- or TAK242-treated group (p < 0.001, when the RAGE mAb or TAK242 group is compared with the saline group). The lesioned cortical tissues of RAGE mAb- or TAK242-treated undercut group showed higher neuronal densities of Nissl staining and higher densities of glutamic acid decarboxylase 67-immunoreactive interneurons than the saline-treated undercut group. Immunostaining to GFAP and Iba-1 revealed lower densities of astrocytes and microglia in the cortex of the treatment groups, suggesting reduced glia activation.

Significance: RAGE and TLR4 signaling are critically involved in posttraumatic epileptogenesis. Blocking these pathways early after traumatic brain injury is a promising strategy for preventing posttraumatic epilepsy.

Is Severe Head Injury Associated with Functional (Psychogenic) Seizures?

Abstract, published in Seizure

Objectives: The aim of the current study was to compare the frequency of significant head injuries in three groups of people with seizures [idiopathic generalized epilepsies (IGE) vs. temporal lobe epilepsy (TLE) vs. functional seizures (FS)].

Methods: This was a retrospective study. All patients with a diagnosis of IGE, TLE, or FS were recruited at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran, from 2008 until 2020.

Results: One thousand and four hundred ninety-two patients were studied (559 patients with IGE, 646 people with TLE, and 287 persons with FS). Overall, 77 (5.2%) individuals of the studied people reported experiencing severe head injuries before the onset of their seizures [9 patients (1.6%) with IGE, 56 people (8.7%) with TLE, and 12 persons (4.2%) with FS; p = 0.0001]. Compared to people with IGE, the odds ratio of having a premorbid history of severe head injury in the FS group was 2.67 [95% Confidence Interval (CI): 1.11-6.40; p = 0.0280]. Compared to people with TLE, the odds ratio of having a premorbid history of severe head injury in the FS group was 0.46 (95% CI: 0.24-0.87; p = 0.0170).

Conclusion: Severe head injury is significantly associated with functional (psychogenic) seizures. However, since head injury is also a significant risk factor for focal epilepsies, it may be necessary to ascertain the diagnosis of post-traumatic seizures by obtaining a detailed clinical history and also by performing video-EEG monitoring in order to adopt an appropriate treatment strategy in these patients.

In-depth Characterization of a Mouse Model of Post-traumatic Epilepsy for Biomarker and Drug Discovery

Abstract, published in Acta Neuropathologica Communications

Post-traumatic epilepsy (PTE) accounts for 5% of all epilepsies and 10–20% of the acquired forms. The latency between traumatic brain injury (TBI) and epilepsy onset in high-risk patients offers a therapeutic window for intervention to prevent or improve the disease course. However, progress towards effective treatments has been hampered by the lack of sensitive prognostic biomarkers of PTE, and of therapeutic targets. There is therefore a pressing clinical need for preclinical PTE models suitable for biomarker discovery and drug testing.

We characterized in-depth a model of severe TBI induced by controlled cortical impact evolving into PTE in CD1 adult male mice. To identify sensitive measures predictive of PTE development and severity, TBI mice were longitudinally monitored by video-electrocorticography (ECoG), examined by MRI, and tested for sensorimotor and cognitive deficits and locomotor activity. At the end of the video-ECoG recording mice were killed for brain histological analysis. PTE occurred in 58% of mice with frequent motor seizures (one seizure every other day), as determined up to 5 months post-TBI. The weight loss of PTE mice in 1 week after TBI correlated with the number of spontaneous seizures at 5 months. Moreover, the recovery rate of the sensorimotor deficit detected by the SNAP test before the predicted time of epilepsy onset was significantly lower in PTE mice than in those without epilepsy. Neuroscore, beam walk and cognitive deficit were similar in all TBI mice. The increase in the contusion volume, the volume of forebrain regions contralateral to the lesioned hemisphere and white matter changes over time assessed by MRI were similar in PTE and no-PTE mice. However, brain histology showed a more pronounced neuronal cell loss in the cortex and hippocampus contralateral to the injured hemisphere in PTE than in no-PTE mice.

The extensive functional and neuropathological characterization of this TBI model, provides a tool to identify sensitive measures of epilepsy development and severity clinically useful for increasing PTE prediction in high-risk TBI patients. The high PTE incidence and spontaneous seizures frequency in mice provide an ideal model for biomarker discovery and for testing new drugs.

Determinants of Caregiver Burden in Male Patients with Epilepsy Following Penetrating Traumatic Brain Injury

Abstract, originally published in Epilepsy & Behavior

Purpose: We determined burden of caring for patients with post-traumatic epilepsy (PTE) following penetrating traumatic brain injury (TBI) and identified factors predicting higher burden.

Method: We assessed 331 caregiver-veteran dyads in Phase 2 (136 PTE, 136 non-PTE, and 59 HC dyads), 133 in Phase 4 (47 PTE, 56 non-PTE, and 30 HC dyads) – 30 years later, and 46 dyads in the follow-up study (18 PTE, 19 non-PTE, and 9 HC). Caregiver’s burden was measured by Zarit Burden Index and a questionnaire. Veterans completed demographic, mental and physical well-being, quality-of-life, and medical-related information. Caregivers provided information about burden and their assessments of cognitive decline and neuropsychiatric status of the veterans.

Results: PTE caregivers perceived significantly more burden than comparison groups at all phases. Bivariate analyses revealed that caregiver distress due to the veteran’s neuropsychiatric state including cognitive decline, apathy, and disinhibition and the veteran’s characteristics including older age at epilepsy onset and role limitation due to physical problems were associated with higher burden. Finally, we revealed disinhibition distress, and role imitation due to physical problems as the predictors in a model of caregiver burden.

Conclusion: Elevated PTE caregiver burden is persistent across the life span suggesting that caregivers could benefit from counseling and targeted psychosocial interventions to reduce their burden.

Preventing Seizures After Brain Injury Could Stave Off Dementia

Summary, originally published by the University of Alberta

Blocking seizures after a head injury could slow or prevent the onset of dementia, according to new research by University of Alberta biologists.

“Traumatic brain injury is a major risk factor for dementia, but the reason this is the case has remained mysterious,” said Ted Allison, co-author and professor in the Department of Biological Sciences in the Faculty of Science. “Through this research, we have discovered one important way they are linked—namely, post-injury seizures.”

“Our data suggest that, at least in animal models, blocking these seizures also could have a benefit later in life by slowing or preventing the onset of dementia,” he explained. “A prophylactic treatment to prevent dementia is an exciting possibility, though there is much work to be done to develop our concept.”

Study Characterizes Mouse Model of Neocortical Injury–Induced Status Epilepticus

Abstract, originally published in Epilepsia

Objective: To characterize neocortical onset status epilepticus (SE) in the C57BL/6J mouse.

Methods: We induced SE by administering homocysteine 16-18 hours after cobalt (Co) implantation. SE was monitored by video and electroencephalography (EEG). We evaluated brain structure with magnetic resonance imaging (MRI). Neurodegeneration was evaluated 72 hours after SE using Fluoro-Jade C staining.

Results: Cobalt triggered seizures in a dose-dependent manner (median effective dose, ED50 = 0.78 mg) and the latency to peak seizure frequency shortened with increased dose. Animals developed SE after homocysteine administration. SE began with early intermittent focal seizures, consisting of frontal onset rhythmic spike-wave discharges manifested as focal dystonia with clonus. These focal seizures then evolved into generalized continuous convulsive activity. Behavioral manifestations of SE included tonic stiffening, bilateral limb clonus, and bilateral tonic-clonic movements, which were accompanied by generalized rhythmic spike-wave discharges on EEG. After prolonged seizures, animals became comatose with intermittent bilateral myoclonic seizures or jerks. During this period, EEG showed seizures interspersed with generalized periodic discharges on a suppressed background. MRI obtained when animals were in a coma revealed edema, midline shift in frontal lobe around the Co implantation site, and ventricular effacement. Fluoro-Jade C staining revealed neurodegeneration in the cortex, amygdala, and thalamus.

Significance: We have developed a mouse model of severe, refractory cortical-onset SE, consisting of convulsions merging into a coma, EEG patterns of cortical seizures, and injury, with evidence of widespread neocortical edema and damage. This model replicates many features of acute seizures and SE resulting from traumatic brain injury, subarachnoid, and lobar hemorrhage.