The Role of the Orexin System in Craniocerebral Trauma-Induced Epilepsy in Mice

BACKGROUND

Following traumatic brain injury (TBI), an imbalance arises in the central nervous system within the hippocampus region, resulting in the proliferation of mossy cell fibers, causing abnormal membrane discharge. Moreover, disruptions in cellular neurotransmitter secretion induce post-traumatic epilepsy. Extensive experimental and clinical data indicate that the orexin system plays a regulatory role in the hippocampal central nervous system, but the specific regulatory effects are unclear. Therefore, further experimental evaluation of its relevance is needed.

OBJECTIVE

This study aims to investigate the effects of orexin receptor agonists (OXA) on the seizure threshold and intensity in controlled cortical impact (CCI) mice, and to understand the role of the orexin system in post-traumatic epilepsy (PTE).

METHODS

Male C57BL/6 mice weighing 18-22 g were randomly divided into three groups: Sham, CCI, and CCI+OXA. The three groups of mice were sequentially constructed with models, implanted with electrodes, and established drug-delivery cannulas. After a 30-day recovery, the Sham and CCI groups were injected with physiological saline through the administration cannulas, while the CCI+OXA group was injected with OXA. Subsequently, all mice underwent electrical stimulation every 30 minutes for a total of 15 times. Epileptic susceptibility, duration, intensity, and cognitive changes were observed. Concurrently, the expression levels and changes of GABAergic neurons in the hippocampus of each group were examined by immunofluorescence.

RESULTS

Injecting OXA into hippocampal CA1 reduces the threshold of post-traumatic seizures, prolongs the post-discharge duration, prolongs seizure duration, reduces cognitive ability, and exacerbates the loss of GABAergic neurons in the hippocampal region.

CONCLUSIONS

Based on the results, we can find that injecting OXA antagonists into the CA1 region of the hippocampus can treat or prevent the occurrence and progression of post-traumatic epilepsy.

Applying Proteomics and Computational Approaches to Identify Novel Targets in Blast-Associated Post-Traumatic Epilepsy

Traumatic brain injury (TBI) can lead to post-traumatic epilepsy (PTE). Blast TBI (bTBI) found in Veterans presents with several complications, including cognitive and behavioral disturbances and PTE; however, the underlying mechanisms that drive the long-term sequelae are not well understood. Using an unbiased proteomics approach in a mouse model of repeated bTBI (rbTBI), this study addresses this gap in the knowledge. After rbTBI, mice were monitored using continuous, uninterrupted video-EEG for up to four months. Following this period, we collected cortex and hippocampus tissues from three groups of mice: those with post-traumatic epilepsy (PTE+), those without epilepsy (PTE-), and the control group (sham). Hundreds of differentially expressed proteins were identified in the cortex and hippocampus of PTE+ and PTE- relative to sham. Focusing on protein pathways unique to PTE+, pathways related to mitochondrial function, post-translational modifications, and transport were disrupted. Computational metabolic modeling using dysregulated protein expression predicted mitochondrial proton pump dysregulation, suggesting electron transport chain dysregulation in the epileptic tissue relative to PTE-. Finally, data mining enabled the identification of several novel and previously validated TBI and epilepsy biomarkers in our data set, many of which were found to already be targeted by drugs in various phases of clinical testing. These findings highlight novel proteins and protein pathways that may drive the chronic PTE sequelae following rbTBI.

Epidemiology, Risk Factors, and Biomarkers of Post-Traumatic Epilepsy: A Comprehensive Overview

This paper presents an in-depth exploration of Post-Traumatic Epilepsy (PTE), a complex neurological disorder following traumatic brain injury (TBI), characterized by recurrent, unprovoked seizures. With TBI being a global health concern, understanding PTE is crucial for effective diagnosis, management, and prognosis. This study aims to provide a comprehensive overview of the epidemiology, risk factors, and emerging biomarkers of PTE, thereby informing clinical practice and guiding future research. The epidemiological aspect of the study reveals PTE as a significant contributor to acquired epilepsies, with varying incidence influenced by injury severity, age, and intracranial pathologies. The paper delves into the multifactorial nature of PTE risk factors, encompassing clinical, demographic, and genetic elements. Key insights include the association of injury severity, intracranial hemorrhages, and early seizures with increased PTE risk, and the roles of age, gender, and genetic predispositions. Advancements in neuroimaging, electroencephalography, and molecular biology are presented, highlighting their roles in identifying potential PTE biomarkers. These biomarkers, ranging from radiological signs to electroencephalography EEG patterns and molecular indicators, hold promise for enhancing PTE pathogenesis understanding, early diagnosis, and therapeutic guidance. The paper also discusses the critical roles of astrocytes and microglia in PTE, emphasizing the significance of neuroinflammation in PTE development. The insights from this review suggest potential therapeutic targets in neuroinflammation pathways. In conclusion, this paper synthesizes current knowledge in the field, emphasizing the need for continued research and a multidisciplinary approach to effectively manage PTE. Future research directions include longitudinal studies for a better understanding of TBI and PTE outcomes, and the development of targeted interventions based on individualized risk profiles. This research contributes significantly to the broader understanding of epilepsy and TBI.

Surgical Outcomes in Post-Traumatic Temporal Lobe Epilepsy: A Systematic Review and Meta-Analysis

Epilepsy surgery provides excellent benefits in post-traumatic epilepsy of the temporal lobe (PTE-TL), but outcomes relative to non-traumatic epilepsy of the temporal lobe (NTE-TL) are less favorable. Large well-designed studies are recommended to further clarify the role of epilepsy surgery in PTE. It is unclear whether epilepsy surgery outcomes in PTE are as robust as described for drug resistant epilepsy (DRE) in general. Prior outcome studies in PTE are limited by small numbers, lack of a control group, or both. We performed a meta-analysis of studies in temporal lobe epilepsy (TLE) to evaluate post-surgical outcomes in those with PTE-TL and compare outcomes to those with NTE-TL. PubMed, EMBASE, and Web of Science databases were queried for studies reporting epilepsy surgery outcomes separately for PTE-TL and NTE-TL. Outcomes were divided into favorable (Engel Class I) or unfavorable (Engel Class II-IV) for comparison. Meta-analyses were performed to evaluate: 1) the proportion of Class I outcomes following epilepsy surgery in PTE-TL; and 2) calculate the odds of Class I surgical outcomes in PTE-TL compared with NTE-TL. Of 3669 articles that reported surgical outcomes in epilepsy, nine studies (n = 886) were identified that reported outcomes for both PTE-TL (n = 219) and NTE-TL (n = 667). The weighted proportion of favorable outcomes (Engel Class I) were high for both PTE-TL (70.1%, 95% CI 61.9%-78.3%) and NTE-TL (75.2%, 95% CI 69.4%-80.2%). Patients with PTE-TL were at greater risk of unfavorable (Engel Class II-IV) outcomes (relative risk 1.36, 95% CI 1.04-1.78) compared with NTE-TL.

Assessing risk factors associated with breakthrough early post-traumatic seizures in patients receiving phenytoin prophylaxis

Objective

Post-traumatic seizure (PTS) is a well-known complication of traumatic brain injury (TBI). The objective of this study was to identify risk factors associated with breakthrough early PTS in TBI patients receiving phenytoin prophylaxis.

Methods

This was a single-centered retrospective study including adult patients admitted to the intensive care unit (ICU), had a TBI, and started on phenytoin for seizure prophylaxis within 24 h of admission. The primary outcome was the incidence and factors associated with early PTS, defined as a confirmed seizure on a continuous electroencephalogram within 7 days of TBI. Secondary outcomes included the association between early post-traumatic seizures and ICU length of stay, hospital length of stay, and in-hospital mortality.

Results

A total of 105 patients were included in the final analysis. Patients with early PTS were older (65 vs. 48 years old, p = 0.01), had a higher Marshall score (5 vs. 2, p = 0.01), were more likely to have a Marshall score > 2 (73 vs. 37%, p = 0.01), and had more neurosurgeries for hematoma evacuation (57 vs. 19%, p = 0.01). In patients with early PTS, 57% had a level at the time of seizure, and of those, 87.5% had a therapeutic level (>10 mcg/mL). Patients with early PTS had a longer ICU length of stay (14.7 vs. 5.9 days, p = 0.04) and a greater proportion of hospital mortality (21 vs. 2%, p = 0.02).

Conclusion

Patients with higher age, Marshall score, and neurosurgical procedures for hematoma evacuation had higher incidences of breakthrough early PTS despite the use of phenytoin prophylaxis. The majority of patients with early PTS had therapeutic phenytoin levels at the time of seizure when a level was available; however, approximately half (43%) did not have a level.

[Predictive capability of Cys112Arg single nucleotide polymorphisms of the apolipoprotein E gene in assessing the risk of immediate and early post-traumatic seizures]

This study is aimed at investigating epileptic seizures, one of the consequences of traumatic brain injury (TBI). Immediate and early post-traumatic seizures, as well as late post-traumatic epileptic seizures or post-traumatic epilepsy, can have different pathogenetic bases. The following key risk factors associated with post-traumatic epilepsy are known: duration of unconsciousness, gunshot wounds, intracranial hemorrhage, diffuse axonal injury, prolonged (more than 3 days) post-traumatic amnesia, acute subdural hematoma with surgical evacuation, immediate and early post-traumatic epileptic seizures, fracture of the skull bones. The role of genetic factors in post-traumatic seizures is poorly understood due to the complexity and multiple causal mechanisms. This paper addresses the role of genetic factors in the occurrence and severity of epileptic events in patients with TBI. In particular, we investigated the role of the Cys112Arg single nucleotide polymorphism of the apolipoprotein E gene. Apolipoprotein E is known for its role in the transport and metabolism of lipids and, therefore, the development of cardiovascular diseases; it is also associated with Alzheimer's disease and has recently been studied in the context of association with epilepsy. The study shows an association between this polymorphism and the risk of immediate and early epileptic seizures in patients with severe TBI.

Treatment of Status Epilepticus after Traumatic Brain Injury Using an Antiseizure Drug Combined with a Tissue Recovery Enhancer Revealed by Systems Biology

We tested a hypothesis that in silico-discovered compounds targeting traumatic brain injury (TBI)-induced transcriptomics dysregulations will mitigate TBI-induced molecular pathology and augment the effect of co-administered antiseizure treatment, thereby alleviating functional impairment. In silico bioinformatic analysis revealed five compounds substantially affecting TBI-induced transcriptomics regulation, including calpain inhibitor, chlorpromazine, geldanamycin, tranylcypromine, and trichostatin A (TSA). In vitro exposure of neuronal-BV2-microglial co-cultures to compounds revealed that TSA had the best overall neuroprotective, antioxidative, and anti-inflammatory effects. In vivo assessment in a rat TBI model revealed that TSA as a monotherapy (1 mg/kg/d) or in combination with the antiseizure drug levetiracetam (LEV 150 mg/kg/d) mildly mitigated the increase in plasma levels of the neurofilament subunit pNF-H and cortical lesion area. The percentage of rats with seizures during 0-72 h post-injury was reduced in the following order: TBI-vehicle 80%, TBI-TSA (1 mg/kg) 86%, TBI-LEV (54 mg/kg) 50%, TBI-LEV (150 mg/kg) 40% (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 30% (p < 0.05). Cumulative seizure duration was reduced in the following order: TBI-vehicle 727 ± 688 s, TBI-TSA 898 ± 937 s, TBI-LEV (54 mg/kg) 358 ± 715 s, TBI-LEV (150 mg/kg) 42 ± 64 (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 109 ± 282 s (p < 0.05). This first preclinical intervention study on post-TBI acute seizures shows that a combination therapy with the tissue recovery enhancer TSA and LEV was safe but exhibited no clear benefit over LEV monotherapy on antiseizure efficacy. A longer follow-up is needed to confirm the possible beneficial effects of LEV monotherapy and combination therapy with TSA on chronic post-TBI structural and functional outcomes, including epileptogenesis.

Advances in understanding the pathogenesis of post-traumatic epilepsy: a literature review

Severe head trauma can lead to seizures. Persistent epileptic seizures and their progression are associated with the severity of trauma. Although case reports have revealed that early use of anti-seizure drugs after trauma can prevent epilepsy, clinical case-control studies have failed to confirm this phenomenon. To date, many brain trauma models have been used to study the correlation between post-traumatic seizures and related changes in neural circuit function. According to these studies, neuronal and glial responses are activated immediately after brain trauma, usually leading to significant cell loss in injured brain regions. Over time, long-term changes in neural circuit tissues, especially in the neocortex and hippocampus, lead to an imbalance between excitatory and inhibitory neurotransmission and an increased risk of spontaneous seizures. These changes include alterations in inhibitory interneurons and the formation of new, over-recurrent excitatory synaptic connections. In this study, we review the progress of research related to post-traumatic epilepsy to better understand the mechanisms underlying the initiation and development of post-traumatic seizures and to provide theoretical references for the clinical treatment of post-traumatic seizures.

Discovery and Validation of Circulating microRNAs as Biomarkers for Epileptogenesis after Experimental Traumatic Brain Injury-The EPITARGET Cohort

Traumatic brain injury (TBI) causes 10-20% of structural epilepsies and 5% of all epilepsies. The lack of prognostic biomarkers for post-traumatic epilepsy (PTE) is a major obstacle to the development of anti-epileptogenic treatments. Previous studies revealed TBI-induced alterations in blood microRNA (miRNA) levels, and patients with epilepsy exhibit dysregulation of blood miRNAs. We hypothesized that acutely altered plasma miRNAs could serve as prognostic biomarkers for brain damage severity and the development of PTE. To investigate this, epileptogenesis was induced in adult male Sprague Dawley rats by lateral fluid-percussion-induced TBI. Epilepsy was defined as the occurrence of at least one unprovoked seizure during continuous 1-month video-electroencephalography monitoring in the sixth post-TBI month. Cortical pathology was analyzed by magnetic resonance imaging on day 2 (D2), D7, and D21, and by histology 6 months post-TBI. Small RNA sequencing was performed from tail-vein plasma samples on D2 and D9 after TBI (n = 16, 7 with and 9 without epilepsy) or sham operation (n = 4). The most promising miRNA biomarker candidates were validated by droplet digital polymerase chain reaction in a validation cohort of 115 rats (8 naïve, 17 sham, and 90 TBI rats [21 with epilepsy]). These included 7 brain-enriched plasma miRNAs (miR-434-3p, miR-9a-3p, miR-136-3p, miR-323-3p, miR-124-3p, miR-212-3p, and miR-132-3p) that were upregulated on D2 post-TBI (p < 0.001 for all compared with naïve rats). The acute post-TBI plasma miRNA profile did not predict the subsequent development of PTE or PTE severity. Plasma miRNA levels, however, predicted the cortical pathology severity on D2 (Spearman ρ = 0.345-0.582, p < 0.001), D9 (ρ = 0.287-0.522, p < 0.001-0.01), D21 (ρ = 0.269-0.581, p < 0.001-0.05) and at 6 months post-TBI (ρ = 0.230-0.433, p < 0.001-0.05). We found that the levels of 6 of 7 miRNAs also reflected mild brain injury caused by the craniotomy during sham operation (ROC AUC 0.76-0.96, p < 0.001-0.05). In conclusion, our findings revealed that increased levels of neuronally enriched miRNAs in the blood circulation after TBI reflect the extent of cortical injury in the brain but do not predict PTE development.

Chemical Kindling as an Experimental Model to Assess the Conventional Drugs in the Treatment of Post-traumatic Epilepsy

BACKGROUND

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality today, which will surpass many infectious diseases in the coming years/decades. Posttraumatic epilepsy (PTE) is one of the most common debilitating consequences of TBI. PTE is a secondary, acquired epilepsy that causes recurrent, spontaneous seizures more than a week after TBI. The extent of head injury in individuals who develop PTE is unknown; however, trauma is thought to account for 20% of symptomatic epilepsy worldwide. Understanding the mechanisms of epilepsy following TBI is crucial for the discovery of new anticonvulsant drugs for the treatment of PTE, as well as for improving the quality of life of patients with PTE.

OBJECTIVE

This review article explains the rationale for the usage of a chemical model to access new treatments for post-traumatic epilepsy.

RESULTS

There are multiple methods to control and manage PTE. The essential and available remedy for the management of epilepsy is the use of antiepileptic drugs. Antiepileptic drugs (AEDs) decrease the frequency of seizures without affecting the disease's causality. Antiepileptic drugs are administrated for the prevention and treatment of PTE; however, 30% of epilepsy patients are drug-resistant, and AED side effects are significant in PTE patients. There are different types of animal models, such as the liquid percussion model, intracortical ferric chloride injection, and cortical subincision model, to study PTE and neurophysiological mechanisms underlying the development of epilepsy after head injury. However, these animal models do not easily mimic the pathological events occurring in epilepsy. Therefore, animal models of PTE are an inappropriate tool for screening new and putatively effective AEDs. Chemical kindling is the most common animal model used to study epilepsy. There is a strong similarity between the kindling model and different types of human epilepsy.

CONCLUSION

Today, researchers use experimental animal models to evaluate new anticonvulsant drugs. The chemical kindling models, such as pentylenetetrazol, bicuculline, and picrotoxin-induced seizures, are important experimental models to analyze the impact of putative antiepileptic drugs.

[The possibilities of Mexidol usage in neuropediatrics]

Mexidol (ethylmethylhydroxypyridine succinate) is a modern neurometabolic medication increasingly being used in neuropediatrics. The results of recent studies confirming the positive effects of Mexidol pharmacotherapy in children with attention deficit hyperactivity disorder (ADHD), perinatal damages of the central nervous system (hypoxic-ischemic encephalopathy) and their consequences, neurological disorders and neurodevelopmental delay after surgery for congenital heart defects, neuroinfections (meningitis, encephalitis), posttraumatic epilepsy. Taking into account the unique multimodal action of Mexidol, it seems promising to expand the range of indications for its application in neuropediatrics, based on the results of new clinical trials organized in accordance with modern principles of evidence-based medicine.

Identification of miRNA-mRNA regulatory network associated with the glutamatergic system in post-traumatic epilepsy rats

Background

Glutamate is one of the most important excitatory neurotransmitters in the mammalian brain and is involved in a variety of neurological disorders. Increasing evidence also shows that microRNA (miRNA) and mRNA pairs are engaged in a variety of pathophysiological processes. However, the miRNA and mRNA pairs that affect the glutamatergic system in post-traumatic epilepsy (PTE) remain unknown.

Methods

PTE rats were induced by injecting 0.1 mol/L, 1 μL/min FeCl₂ solution. Behavioral scores and EEG monitoring were used to evaluate whether PTE was successfully induced. RNA-seq was used to obtain mRNA and miRNA expression profiles. Bioinformatics analysis was performed to screen differentially expressed mRNAs and miRNAs associated with the glutamatergic system and then predict miRNA-mRNA interaction pairs. Real-time quantitative reverse transcription PCR was used to further validate the expression of the differential miRNAs and mRNAs. The microRNA-mRNA was subject to the Pearson correlation analysis.

Results

Eight of the 91 differentially expressed mRNAs were associated with the glutamatergic system, of which six were upregulated and two were downregulated. Forty miRNAs were significantly differentially expressed, with 14 upregulated and 26 downregulated genes. The predicted miRNA-mRNA interaction network shows that five of the eight differentially expressed mRNAs associated with the glutamatergic system were targeted by multiple miRNAs, including Slc17a6, Mef2c, Fyn, Slc25a22, and Shank2, while the remaining three mRNAs were not targeted by any miRNAs. Of the 40 differentially expressed miRNAs, seven miRNAs were found to have multiple target mRNAs associated with the glutamatergic system. Real-time quantitative reverse transcription PCR validation and Pearson correlation analysis were performed on these seven targeted miRNAs-Slc17a6, Mef2c, Fyn, Slc25a22, and Shank2-and six additional miRNAs selected from the literature. Real-time quantitative reverse transcription PCR showed that the expression levels of the mRNAs and miRNAs agreed with the predictions in the study. Among them, the miR-98-5p-Slc17a6, miR-335-5p-Slc17a6, miR-30e-5p-Slc17a6, miR-1224-Slc25a22, and miR-211-5p-Slc25a22 pairs were verified to have negative correlations.

Conclusions

Our results indicate that miRNA-mRNA interaction pairs associated with the glutamatergic system are involved in the development of PTE and have potential as diagnostic biomarkers and therapeutic targets for PTE.

Plasma Neurofilament Light Chain (NF-L) Is a Prognostic Biomarker for Cortical Damage Evolution but Not for Cognitive Impairment or Epileptogenesis Following Experimental TBI

Plasma neurofilament light chain (NF-L) levels were assessed as a diagnostic biomarker for traumatic brain injury (TBI) and as a prognostic biomarker for somatomotor recovery, cognitive decline, and epileptogenesis. Rats with severe TBI induced by lateral fluid-percussion injury (n = 26, 13 with and 13 without epilepsy) or sham-operation (n = 8) were studied. During a 6-month follow-up, rats underwent magnetic resonance imaging (MRI) (day (D) 2, D7, and D21), composite neuroscore (D2, D6, and D14), Morris-water maze (D35−D39), and a 1-month-long video-electroencephalogram to detect unprovoked seizures during the 6th month. Plasma NF-L levels were assessed using a single-molecule assay at baseline (i.e., naïve animals) and on D2, D9, and D178 after TBI or a sham operation. Plasma NF-L levels were 483-fold higher on D2 (5072.0 ± 2007.0 pg/mL), 89-fold higher on D9 (930.3 ± 306.4 pg/mL), and 3-fold higher on D176 32.2 ± 8.9 pg/mL after TBI compared with baseline (10.5 ± 2.6 pg/mL; all p < 0.001). Plasma NF-L levels distinguished TBI rats from naïve animals at all time-points examined (area under the curve [AUC] 1.0, p < 0.001), and from sham-operated controls on D2 (AUC 1.0, p < 0.001). Plasma NF-L increases on D2 were associated with somatomotor impairment severity (ρ = −0.480, p < 0.05) and the cortical lesion extent in MRI (ρ = 0.401, p < 0.05). Plasma NF-L increases on D2 or D9 were associated with the cortical lesion extent in histologic sections at 6 months post-injury (ρ = 0.437 for D2; ρ = 0.393 for D9, p < 0.05). Plasma NF-L levels, however, did not predict somatomotor recovery, cognitive decline, or epileptogenesis (p > 0.05). Plasma NF-L levels represent a promising noninvasive translational diagnostic biomarker for acute TBI and a prognostic biomarker for post-injury somatomotor impairment and long-term structural brain damage.

Differential Patterns of Change in Brain Connectivity Resulting from Severe Traumatic Brain Injury

Background: Traumatic brain injury (TBI) damages white matter tracts, disrupting brain network structure and communication. There exists a wide heterogeneity in the pattern of structural damage associated with injury, as well as a large heterogeneity in behavioral outcomes. However, little is known about the relationship between changes in network connectivity and clinical outcomes. Materials and Methods: We utilize the rat lateral fluid-percussion injury model of severe TBI to study differences in brain connectivity in 8 animals that received the insult and 11 animals that received only a craniectomy. Diffusion tensor imaging is performed 5 weeks after the injury and network theory is used to investigate changes in white matter connectivity. Results: We find that (1) global network measures are not able to distinguish between healthy and injured animals; (2) injury induced alterations predominantly exist in a subset of connections (subnetworks) distributed throughout the brain; and (3) injured animals can be divided into subgroups based on changes in network motifs-measures of local structural connectivity. In addition, alterations in predicted functional connectivity indicate that the subgroups have different propensities to synchronize brain activity, which could relate to the heterogeneity of clinical outcomes. Discussion: These results suggest that network measures can be used to quantify progressive changes in brain connectivity due to injury and differentiate among subpopulations with similar injuries, but different pathological trajectories.

Risk Factors and Incidence of Epilepsy after Severe Traumatic Brain Injury

We determined the incidence of post-traumatic epilepsy after severe traumatic brain injury. Of 392 patients surviving to discharge, cumulative incidence of post-traumatic epilepsy was 25% at 5 years and 32% at 15 years, an increase compared with historical reports. Among patients with one late seizure (>7 days post-trauma), the risk of seizure recurrence was 62% after 1 year and 82% at 10 years. Competing hazards regression identified age, decompressive hemicraniectomy, and intracranial infection as independent predictors of post-traumatic epilepsy. Patients with severe traumatic brain injury and a single late post-traumatic seizure will likely require long-term antiseizure medicines. ANN NEUROL 2022;92:663-669.

Adult Born Dentate Granule Cell Mediated Upregulation of Feedback Inhibition in a Mouse Model of Traumatic Brain Injury

Post-traumatic epilepsy (PTE) and behavioral comorbidities frequently develop after traumatic brain injury (TBI). Aberrant neurogenesis of dentate granule cells (DGCs) after TBI may contribute to the synaptic reorganization that occurs in PTE, but how neurogenesis at different times relative to the injury contributes to feedback inhibition and recurrent excitation in the dentate gyrus is unknown. Thus, we examined whether DGCs born at different postnatal ages differentially participate in feedback inhibition and recurrent excitation in the dentate gyrus using the controlled cortical impact (CCI) model of TBI. Both sexes of transgenic mice expressing channelrhodopsin2 (ChR2) in postnatally born DGCs were used for optogenetic activation of three DGC cohorts: postnatally early born DGCs, or those born just before or after CCI. We performed whole-cell patch-clamp recordings from ChR2-negative, mature DGCs and parvalbumin-expressing basket cells (PVBCs) in hippocampal slices to determine whether optogenetic activation of postnatally born DGCs increases feedback inhibition and/or recurrent excitation in mice 8-10 weeks after CCI and whether PVBCs are targets of ChR2-positive DGCs. In the dentate gyrus ipsilateral to CCI, activation of ChR2-expressing DGCs born before CCI produced increased feedback inhibition in ChR2-negative DGCs and increased excitation in PVBCs compared with those from sham controls. This upregulated feedback inhibition was less prominent in DGCs born early in life or after CCI. Surprisingly, ChR2-positive DGC activation rarely evoked recurrent excitation in mature DGCs from any cohort. These results support that DGC birth date-related increased feedback inhibition in of DGCs may contribute to altered excitability after TBI.SIGNIFICANCE STATEMENT Dentate granule cells (DGCs) control excitability of the dentate gyrus through synaptic interactions with inhibitory GABAergic interneurons. Persistent changes in DGC synaptic connectivity develop after traumatic brain injury, contributing to hyperexcitability in post-traumatic epilepsy (PTE). However, the impact of DGC neurogenesis on synaptic reorganization, especially on inhibitory circuits, after brain injury is not adequately described. Here, upregulation of feedback inhibition in mature DGCs from male and female mice was associated with increased excitation of parvalbumin-expressing basket cells by postnatally born DGCs, providing novel insights into underlying mechanisms of altered excitability after brain injury. A better understanding of these inhibitory circuit changes can help formulate hypotheses for development of novel, evidence-based treatments for post-traumatic epilepsy by targeting birth date-specific subsets of DGCs.

Risk factors for Drug-resistant Epilepsy (DRE) and a nomogram model to predict DRE development in post-traumatic epilepsy patients

Objectives

To identify factors affecting the development of drug‐resistant epilepsy (DRE), and establish a reliable nomogram to predict DRE development in post‐traumatic epilepsy (PTE) patients.

Methods

This study conducted a retrospective clinical analysis in patients with PTE who visited the Epilepsy Center, Beijing Tiantan Hospital from January 2013 to December 2018. All participants were followed up for at least 3 years, and the development of DRE was assessed. Data from January 2013 to December 2017 were used as development dataset for model building. Those independent predictors of DRE were included in the final multivariable logistic regression, and a derived nomogram was built. Data from January 2018 to December 2018 were used as validation dataset for internal validation.

Results

Complete clinical information was available for 2830 PTE patients (development dataset: 2023; validation dataset: 807), of which 21.06% (n = 596) developed DRE. Among all parameters of interest including gender, age at PTE, family history, severity of traumatic brain injury (TBI), single or multiple injuries, lesion location, post‐TBI treatments, acute seizures, PTE latency, seizure type, status epilepticus (SE), and electroencephalogram (EEG) findings, four predictors showed independent effect on DRE, they were age at PTE, seizure type, SE, and EEG findings. A model incorporating these four variables was created, and a nomogram to calculate the probability of DRE using the coefficients of the model was developed. The C‐index of the predictive model and the validation was 0.662 and 0.690, respectively. The goodness‐of‐fit test indicated good calibration for model development and validation (p = 0.272, 0.572).

Conclusions

The proposed nomogram achieved significant potential for clinical utility in the prediction of DRE among PTE patients. The risk of DRE for individual PTE patients can be estimated by using this nomogram, and identified high‐risk patients might benefit from non‐pharmacological therapies at an early stage.

Predicting Global Functional Outcomes Among Post-traumatic Epilepsy Patients After Moderate-to-Severe Traumatic Brain Injury: Development of a Prognostic Model

Objective

The development of post-traumatic epilepsy (PTE) following traumatic brain injury (TBI) is associated with unfavorable functional outcomes, and the global function of PTE patients might change dynamically overtime. Predicting the long-term functional outcomes of patients with PTE may help to develop accurate rehabilitation programs and improve their quality of life. Based on this, the objective of this study is to use clinical data to derive and validate a model for predicting the functional outcomes of patients with PTE after moderate-to-severe TBI.

Methods

This study retrospectively analyzed 721 patients with PTE after moderate-to-severe TBI in the Epilepsy Centre, Beijing Tiantan Hospital, from January 2013 to December 2018. All patients had favorable global function as indicated by the Glasgow Outcome Scale-Extended (GOSE) at the time of their first late post-traumatic seizure (PTS) onset, and the 5-year global function after the first late PTS onset was chosen as the principal outcome of interest. To identify possible predictors for the global functional outcomes, univariate and multivariate logistic regression techniques were used. A prognostic model was established using these identified predictors, the internal validation with the bootstrapping method was performed, and the model was then visualized as a graphical score chart.

Results

The 5-year global functional outcome of 98 (13.59%) patients was unfavorable, and the temporal lobe lesion was found as the strongest predictor of unfavorable outcomes. The final prognostic model also included the following other predictors: gender, age at TBI, multiple injuries, the severity of TBI, and latency of PTE. Discrimination was satisfactory with C-statistic of 0.754 (0.707 – 0.800), the goodness-of-fit test indicated good calibration (P = 0.137), and the C-statistic was 0.726 for internal validation. A graphical score chart was also constructed to provide the probability of an unfavorable 5-year global functional outcomes more readily.

Conclusions

Clearer treatment strategies are essential to help ameliorate the global functional outcomes of patients with PTE. Our proposed prognostic model has significant potential to be used in the clinic for predicting global functional outcomes among patients with PTE after moderate-to-severe TBI.

Robust, long-term video EEG monitoring in a porcine model of post-traumatic epilepsy

To date, post-traumatic epilepsy (PTE) research in large animal models has been limited. Recent advances in neocortical microscopy have made possible new insights into neocortical PTE. However, it is very difficult to engender convincing neocortical PTE in rodents. Thus, large animal models that develop neocortical PTE may provide useful insights that also can be more comparable to human patients. Because gyrencephalic species have prolonged latent periods, long-term video EEG recording is required. Here, we report a fully subcutaneous EEG implant with synchronized video in freely ambulatory swine for up to 13 months during epileptogenesis following bilateral cortical impact injuries or sham surgery The advantages of this system include the availability of a commercially available system that is simple to install, a low failure rate after surgery for EEG implantation, radiotelemetry that enables continuous monitoring of freely ambulating animals, excellent synchronization to video to EEG, and a robust signal to noise ratio. The disadvantages of this system in this species and age are the accretion of skull bone which entirely embedded a subset of skull screws and EEG electrodes, and the inability to rearrange the EEG electrode array. These disadvantages may be overcome by splicing a subdural electrode strip to the electrode leads so that skull growth is less likely to interfere with long-term signal capture and by placing two implants for a more extensive montage. This commercially available system in this bilateral cortical impact swine model may be useful to a wide range of investigators studying epileptogenesis in PTE.SignificancePost-traumatic epilepsy (PTE) is a cause of significant morbidity after traumatic brain injury (TBI) and is often drug-resistant. Robust, informative animal models would greatly facilitate PTE research. Ideally, this biofidelic model of PTE would utilize a species that approximates human brain anatomy, brain size, glial populations, and inflammatory pathways. An ideal model would also incorporate feasible methods for long-term video EEG recording required to quantify seizure activity. Here, we describe the first model of PTE in swine and describe a method for robust long-term video EEG monitoring for up to 13 months post-TBI. The relatively easy "out-of-the-box" radiotelemetry system and surgical techniques described here will be adaptable by a wide array of investigators studying the pathogenesis and treatment of PTE.

A Comprehensive and Advanced Mouse Model of Post-Traumatic Epilepsy with Robust Spontaneous Recurrent Seizures

Traumatic brain injury (TBI) is a leading cause of epilepsy in military persons and civilians. Spontaneous recurrent seizures (SRSs) 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 mechanisms and interventions related to TBI-induced epilepsy. Despite many attempts to induce PTE in animals, success has been limited due to a lack of consistent SRSs after TBI. We present a comprehensive protocol to induce PTE after contusion brain injury in mice, which exhibit robust SRSs along with neurodegeneration and neuroinflammation. This article provides a complete set of protocols for injury, outcomes, troubleshooting, and data analysis. Our broad profiling of a TBI mouse reveals features of progressive, long-lasting epileptic activity, hippocampal sclerosis, and comorbid mood and memory deficits. Overall, the PTE mouse shows striking consistency in recapitulating major hallmark features of human PTE. This mouse model will be helpful in assessing mechanisms of and interventions for TBI-induced epileptogenesis, epilepsy, and neuropsychiatric dysfunction. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Inducing controlled cortical impact injuries Support Protocol: Creating the custom domed camp Basic Protocol 2: Recording long-term video-EEG signals Basic Protocol 3: Analyzing video-EEG recordings.

Seizure Susceptibility and Sleep Disturbance as Biomarkers of Epileptogenesis after Experimental TBI

Objectives: We investigated whether seizure susceptibility increases over weeks−months after experimental traumatic brain injury (TBI), and whether seizure susceptibility in rats predicts the development of post-traumatic epilepsy (PTE) or epileptiform activity. We further investigated whether rats develop chronic sleep disturbance after TBI, and whether sleep disturbance parameters—alone or in combination with pentylenetetrazol (PTZ) test parameters—could serve as novel biomarkers for the development of post-traumatic epileptogenesis. Methods: TBI was induced in adult male Sprague-Dawley rats with lateral fluid-percussion injury. Sham-operated experimental controls underwent craniectomy without exposure to an impact force. Seizure susceptibility was tested with a PTZ test (30 mg/kg, intraperitoneally) on day (D) 30, D60, D90, and D180 after TBI (n = 28) or sham operation (n = 16) under video electroencephalogram (vEEG). In the 7th post-injury month, rats underwent continuous vEEG monitoring to detect spontaneous seizures and assess sleep disturbances. At the end of the experiments, rats were perfused for brain histology. Results: In the TBI group, the percentage of rats with PTZ-induced seizures increased over time (adjusted p < 0.05 compared with D30). Combinations of three PTZ test parameters (latency to the first epileptiform discharge (ED), number of EDs, and number of PTZ-induced seizures) survived the leave-one-out validation for differentiating rats with or without epileptiform activity, indicating an area under the receiver operating curve (AUC) of 0.743 (95% CI 0.472−0.992, p = 0.05) with a misclassification rate of 36% on D90, and an AUC of 0.752 (95% CI 0.483−0.929, p < 0.05) with a misclassification rate of 32% on D180. Sleep analysis revealed that the number of transitions to N3 or rapid eye movement (REM) sleep, along with the total number of transitions, was increased in the TBI group during the lights-on period (all p < 0.05). The sleep fragmentation index during the lights-on period was greater in the TBI rats than in sham-operated rats (p < 0.05). A combination of sleep parameters showed promise as diagnostic biomarkers of prior TBI, with an AUC of 0.792 (95% CI 0.549−0.934, p < 0.01) and a misclassification rate of 28%. Rats with epilepsy or any epileptiform activity had more transitions from N3 to the awake stage (p < 0.05), and the number of N3−awake transitions differentiated rats with or without epileptiform activity, with an AUC of 0.857 (95% CI 0.651−1.063, p < 0.01). Combining sleep parameters with PTZ parameters did not improve the biomarker performance. Significance: This is the first attempt to monitor the evolution of seizure susceptibility over months in a well-described rat model of PTE. Our data suggest that assessment of seizure susceptibility and sleep disturbance can provide diagnostic biomarkers of prior TBI and prognostic biomarkers of post-traumatic epileptogenesis.

Hippocampal position and orientation as prognostic biomarkers for post-traumatic epileptogenesis - an experimental study in rat lateral fluid-percussion model

Objective

This study was undertaken to identify prognostic biomarkers for posttraumatic epileptogenesis derived from parameters related to the hippocampal position and orientation.

Methods

Data were derived from two preclinical magnetic resonance imaging (MRI) follow‐up studies: EPITARGET (156 rats) and Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx; University of Eastern Finland cohort, 43 rats). Epileptogenesis was induced with lateral fluid percussion‐induced traumatic brain injury (TBI) in adult male Sprague Dawley rats. In the EPITARGET cohort, T2∗‐weighted MRI was performed at 2, 7, and 21 days and in the EpiBioS4Rx cohort at 2, 9, and 30 days and 5 months post‐TBI. Both hippocampi were segmented using convolutional neural networks. The extracted segmentation mask was used for a geometric construction, extracting 39 parameters that described the position and orientation of the left and right hippocampus. In each cohort, we assessed the parameters as prognostic biomarkers for posttraumatic epilepsy (PTE) both individually, using repeated measures analysis of variance, and in combination, using random forest classifiers.

Results

The extracted parameters were highly effective in discriminating between sham‐operated and TBI rats in both the EPITARGET and EpiBioS4Rx cohorts at all timepoints (t; balanced accuracy > .9). The most discriminating parameter was the inclination of the hippocampus ipsilateral to the lesion at t = 2 days and the volumes at t ≥ 7 days after TBI. Furthermore, in the EpiBioS4Rx cohort, we could effectively discriminate epileptogenic from nonepileptogenic animals with a longer MRI follow‐up, at t = 150 days (area under the curve = .78, balanced accuracy = .80, p = .0050), based on the orientation of both hippocampi. We found that the ipsilateral hippocampus rotated outward on the horizontal plane, whereas the contralateral hippocampus rotated away from the vertical direction.

Significance

We demonstrate that assessment of TBI‐induced hippocampal deformation by clinically translatable MRI methodologies detects subjects with prior TBI as well as those at high risk of PTE, paving the way toward subject stratification for antiepileptogenesis studies.

Susceptibility to epilepsy after traumatic brain injury is associated with preexistent gut microbiome profile

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 LFPI 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 SCFA content.

Peripheral Infection after Traumatic Brain Injury Augments Excitability in the Perilesional Cortex and Dentate Gyrus

Peripheral infections occur in up to 28% of patients with traumatic brain injury (TBI), which is a major etiology for structural epilepsies. We hypothesized that infection occurring after TBI acts as a “second hit” and facilitates post-traumatic epileptogenesis. Adult male Sprague–Dawley rats were subjected to lateral fluid-percussion injury or sham-operation. At 8 weeks post-injury, rats were treated with lipopolysaccharide (LPS, 5 mg/kg) to mimic Gram-negative peripheral infection. T2-weighted magnetic resonance imaging was used to detect the cortical lesion type (small focal inflammatory [TBI_FI] vs. large cavity-forming [TBI_CF]). Spontaneous seizures were detected with video-electroencephalography, and seizure susceptibility was determined by the pentylenetetrazole (PTZ) test. Post-PTZ neuronal activation was assessed using c-Fos immunohistochemistry. LPS treatment increased the percentage of rats with PTZ-induced seizures among animals with TBI_FI lesions (p < 0.05). It also increased the cumulative duration of PTZ-induced seizures (p < 0.01), particularly in the TBI_FI group (p < 0.05). The number of c-Fos immunopositive cells was higher in the perilesional cortex of injured animals compared with sham-operated animals (p < 0.05), particularly in the TBI-LPS group (p < 0.05). LPS treatment increased the percentage of injured rats with bilateral c-Fos staining in the dentate gyrus (p < 0.05), particularly in the TBI_FI group (p < 0.05). Our findings demonstrate that peripheral infection after TBI increases PTZ-induced seizure susceptibility and neuronal activation in the perilesional cortex and bilaterally in the dentate gyrus, particularly in animals with prolonged perilesional T2 enhancement. Our data suggest that treatment of infections and reduction of post-injury neuro-inflammation are important components of the treatment regimen aiming at preventing epileptogenesis after TBI.

Post-Traumatic Epilepsy in Zebrafish Is Drug-Resistant and Impairs Cognitive Function

Post-traumatic epilepsy (PTE) is acquired epilepsy after traumatic brain injury (TBI). Despite the availability of more than 20 antiseizure medications (ASMs), there is no way at present to prevent epileptogenesis in TBI survivors, and many cases of PTE become drug-resistant. Importantly, the adverse effects of ASMs can significantly affect patients' quality of life. Mammalian models are commonly used for studying refractory PTE, but are expensive and laborious. Zebrafish models have become popular for studying epilepsy, but most focus on larvae, and there have been no reports to date of pharmacological screening in an adult zebrafish model of acquired epilepsy. Valid animal models are critical for understanding PTE and for developing novel therapeutics. The aim of the present study was to characterize the cognitive impairments of a zebrafish model of TBI that leads to the development of PTE. Using combined behavioral and electrophysiological approaches, we also characterized the pharmacological effects of the most commonly used ASMs to manage PTE (valproate, carbamazepine, and phenytoin). Zebrafish with PTE exhibited impairments in learning and memory, difficulty in decision making, and reduced social preference. Valproate and carbamazepine had a limited protective effect against behavioral seizures, and all three drugs failed to significantly reduce electrographical seizures. The negative impacts of TBI and ASMs in zebrafish parallel those observed in other animals, making the zebrafish model of PTE a promising high-throughput model of refractory and drug-resistant epilepsy.

The Military Injuries: Understanding Post-Traumatic Epilepsy Study: Understanding Relationships among Lifetime Traumatic Brain Injury History, Epilepsy, and Quality of Life

Understanding risk for epilepsy among persons who sustain a mild (mTBI) traumatic brain injury (TBI) is crucial for effective intervention and prevention. However, mTBI is frequently undocumented or poorly documented in health records. Further, health records are non-continuous, such as when persons move through health systems (e.g., from Department of Defense to Veterans Affairs [VA] or between jobs in the civilian sector), making population-based assessments of this relationship challenging. Here, we introduce the MINUTE (Military INjuries-Understanding post-Traumatic Epilepsy) study, which integrates data from the Veterans Health Administration with self-report survey data for post-9/11 veterans (n = 2603) with histories of TBI, epilepsy and controls without a history of TBI or epilepsy. This article describes the MINUTE study design, implementation, hypotheses, and initial results across four groups of interest for neurotrauma: 1) control; 2) epilepsy; 3) TBI; and 4) post-traumatic epilepsy (PTE). Using combined survey and health record data, we test hypotheses examining lifetime history of TBI and the differential impacts of TBI, epilepsy, and PTE on quality of life. The MINUTE study revealed high rates of undocumented lifetime TBIs among veterans with epilepsy who had no evidence of TBI in VA medical records. Further, worse physical functioning and health-related quality of life were found for persons with epilepsy + TBI compared to those with either epilepsy or TBI alone. This effect was not fully explained by TBI severity. These insights provide valuable opportunities to optimize the resilience, delivery of health services, and community reintegration of veterans with TBI and complex comorbidity.

The Role of Neuroinflammation in Post-traumatic Epilepsy

Post-traumatic epilepsy (PTE) is one of the consequences after traumatic brain injury (TBI), which increases the morbidity and mortality of survivors. About 20% of patients with TBI will develop PTE, and at least one-third of them are resistant to conventional antiepileptic drugs (AEDs). Therefore, it is of utmost importance to explore the mechanisms underlying PTE from a new perspective. More recently, neuroinflammation has been proposed to play a significant role in epileptogenesis. This review focuses particularly on glial cells activation, peripheral leukocytes infiltration, inflammatory cytokines release and chronic neuroinflammation occurrence post-TBI. Although the immune response to TBI appears to be primarily pro-epileptogenic, further research is needed to clarify the causal relationships. A better understanding of how neuroinflammation contributes to the development of PTE is of vital importance. Novel prevention and treatment strategies based on the neuroinflammatory mechanisms underlying epileptogenesis are evidently needed.

Search Strategy

Search MeSH Terms in pubmed: "["Epilepsy"(Mesh)] AND "Brain Injuries, Traumatic"[Mesh]". Published in last 30 years. 160 results were founded. Full text available:145 results. Record screened manually related to Neuroinflammation and Post-traumatic epilepsy. Then finally 123 records were included.

Post-Traumatic Seizures: A Deep-Dive Into Pathogenesis

Post-traumatic seizures (PTS) have become an emerging challenge for neurologists worldwide with the rise of brain injuries. Trauma can lead to various outcomes, ranging from naive spasms to debilitating post-traumatic epilepsy (PTE). In this article, we will explore the pathogenesis of convulsions following a concussion. We will look at multiple studies to explain the various structural, metabolic, and inflammatory changes leading to seizures. Additionally, we will explore the association between severity and location of injury and PTE. PTE's pathophysiology is not entirely implicit, and we are still in the dark as to which anti-epileptic drugs will be useful in circumventing these attacks. The purpose of this narrative review is to explain the post-traumatic brain changes in detail so that such attacks can be either thwarted or treated more resourcefully in the future.

Neuropathophysiological Mechanisms and Treatment Strategies for Post-traumatic Epilepsy

Traumatic brain injury (TBI) is a leading cause of death in young adults and a risk factor for acquired epilepsy. Severe TBI, after a period of time, causes numerous neuropsychiatric and neurodegenerative problems with varying comorbidities; and brain homeostasis may never be restored. As a consequence of disrupted equilibrium, neuropathological changes such as circuit remodeling, reorganization of neural networks, changes in structural and functional plasticity, predisposition to synchronized activity, and post-translational modification of synaptic proteins may begin to dominate the brain. These pathological changes, over the course of time, contribute to conditions like Alzheimer disease, dementia, anxiety disorders, and post-traumatic epilepsy (PTE). PTE is one of the most common, devastating complications of TBI; and of those affected by a severe TBI, more than 50% develop PTE. The etiopathology and mechanisms of PTE are either unknown or poorly understood, which makes treatment challenging. Although anti-epileptic drugs (AEDs) are used as preventive strategies to manage TBI, control acute seizures and prevent development of PTE, their efficacy in PTE remains controversial. In this review, we discuss novel mechanisms and risk factors underlying PTE. We also discuss dysfunctions of neurovascular unit, cell-specific neuroinflammatory mediators and immune response factors that are vital for epileptogenesis after TBI. Finally, we describe current and novel treatments and management strategies for preventing PTE.

Diversity of kindling of limbic seizures after lateral fluid percussion injury in the rat

Lateral fluid percussion injury (LFPI) in rats is used to model post-traumatic epilepsy (PTE), with spontaneous seizures occurring in up to ½ of the subjects. Using the kindling paradigm, we examined whether animals without detectable seizures had an altered seizure susceptibility. Male Sprague Dawley rats were subjected to LFPI. Seven-nine months later, spontaneous seizures were monitored for two weeks. Afterward, the animals underwent kindling of basolateral amygdala. For kindling outcomes, the animals were categorized based on the 95% confidence intervals of mean number trials to kindling (ie 3 consecutive stage 4-5 seizures). Spontaneous seizures were detected in 7 out of 24 rats. There was no correlation between the severity of LFPI and either baseline afterdischarge properties, or kindling rates. Six LFPI rats kindled at a rate comparable to those in sham-LFPI (n = 10) and in naïve (n = 7) subjects. Ten LFPI rats kindled faster and 8-slower than controls. None of slow-kindling rats had spontaneous seizures during the prekindling monitoring. During the same period, six fast-kindling and three normal-kindling rats had been seizure-free. Thus, kindling reveals a diversity to seizure susceptibility after LFPI beyond an overt seizure symptomatology, ranging from the increased susceptibility to the increased resistance.

Identification of MicroRNA-Potassium Channel Messenger RNA Interactions in the Brain of Rats With Post-traumatic Epilepsy

Background: Dysregulated expression of microRNAs and potassium channels have been reported for their contributions to seizure onset. However, the microRNA–potassium channel gene interactions in traumatic brain injury-induced post-traumatic epilepsy (PTE) remain unknown.

Methods: PTE was induced in male rats by intracranial injection with ferrous chloride (0.1 mol/L, 1 μl/min) at the right frontal cortex. Electroencephalography was recorded at 60 min, as well as day 1, 7, and 30, and the behavioral seizures were assessed before injection and at different time points after injection. Rats were killed on day 30 after injection. The right frontal cortex samples were collected and subjected to high throughput messenger RNA (mRNA) and microRNA sequencing. A network of differentially expressed potassium channel mRNAs and microRNAs was constructed using OryCun2.0 and subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. The differential mRNA and microRNA expressions were verified using quantitative real-time-PCR. The microRNA–mRNA was subject to the Pearson correlation analysis.

Results: A PTE rat model was successfully established, as evidenced by behavioral seizures and epileptiform discharges on electroencephalography in PTE rats compared with sham rats. Among the 91 mRNAs and 40 microRNAs that were significantly differentially expressed in the PTE rat brain, 4 mRNAs and 10 microRNAs were associated with potassium channels. Except for potassium calcium-activated channel subfamily N member 2, the other three potassium channel mRNAs were negatively correlated with seven microRNAs. These microRNA–mRNA pairs were enriched in annotations and pathways related to neuronal ion channels and neuroinflammation. Quantitative real-time-PCR and correlation analysis verified negative correlations in miR-449a-5p-KCNH2, miR-98-5p-KCNH2, miR-98-5p-KCNK15, miR-19b-3p-KCNK15, and miR-301a-3p-KCNK15 pairs.

Conclusion: We identified microRNA–potassium channel mRNA interactions associated with PTE, providing potential diagnostic markers and therapeutic targets for PTE.

Iron Metabolism and Ferroptosis in Epilepsy

Epilepsy is a disease characterized by recurrent, episodic, and transient central nervous system (CNS) dysfunction resulting from an excessive synchronous discharge of brain neurons. It is characterized by diverse etiology, complex pathogenesis, and difficult treatment. In addition, most epileptic patients exhibit social cognitive impairment and psychological impairment. Iron is an essential trace element for human growth and development and is also involved in a variety of redox reactions in organisms. However, abnormal iron metabolism is associated with several neurological disorders, including hemorrhagic post-stroke epilepsy and post-traumatic epilepsy (PTE). Moreover, ferroptosis is also considered a new form of regulation of cell death, which is attributed to severe lipid peroxidation caused by the production of reactive oxygen species (ROS) and iron overload found in various neurological diseases, including epilepsy. Therefore, this review summarizes the study on iron metabolism and ferroptosis in epilepsy, in order to elucidate the correlation between iron and epilepsy. It also provides a novel method for the treatment, prevention, and research of epilepsy, to control epileptic seizures and reduce nerve injury after the epileptic seizure.

Multiplex Networks to Characterize Seizure Development in Traumatic Brain Injury Patients

Traumatic brain injury (TBI) may cause secondary debilitating problems, such as post-traumatic epilepsy (PTE), which occurs with unprovoked recurrent seizures, months or even years after TBI. Currently, the Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx) has been enrolling moderate-severe TBI patients with the goal to identify biomarkers of epileptogenesis that may help to prevent seizure occurrence and better understand the mechanism underlying PTE. In this work, we used a novel complex network approach based on segmenting T1-weighted Magnetic Resonance Imaging (MRI) scans in patches of the same dimension (network nodes) and measured pairwise patch similarities using Pearson's correlation (network connections). This network model allowed us to obtain a series of single and multiplex network metrics to comprehensively analyze the different interactions between brain components and capture structural MRI alterations related to seizure development. We used these complex network features to train a Random Forest (RF) classifier and predict, with an accuracy of 70 and a 95% confidence interval of [67, 73%], which subjects from EpiBioS4Rx have had at least one seizure after a TBI. This complex network approach also allowed the identification of the most informative scales and brain areas for the discrimination between the two clinical groups: seizure-free and seizure-affected subjects, demonstrating to be a promising pilot study which, in the future, may serve to identify and validate biomarkers of PTE.

Genetic Contributions to Acquired Epilepsies

Whether genetic factors contribute to acquired epilepsies has long been controversial. Supporters observe that, among individuals exposed to seemingly the same brain insult, only a minority develops unprovoked seizures. Yet, only in relatively recent years have studies started to build a case for genetic contributions. Here, we appraise this emerging evidence, by providing a critical review of studies published in the field.

A Translational Study on Acute Traumatic Brain Injury: High Incidence of Epileptiform Activity on Human and Rat Electrocorticograms and Histological Correlates in Rats

Background: In humans, early pathological activity on invasive electrocorticograms (ECoGs) and its putative association with pathomorphology in the early period of traumatic brain injury (TBI) remains obscure. Methods: We assessed pathological activity on scalp electroencephalograms (EEGs) and ECoGs in patients with acute TBI, early electrophysiological changes after lateral fluid percussion brain injury (FPI), and electrophysiological correlates of hippocampal damage (microgliosis and neuronal loss), a week after TBI in rats. Results: Epileptiform activity on ECoGs was evident in 86% of patients during the acute period of TBI, ECoGs being more sensitive to epileptiform and periodic discharges. A “brush-like” ECoG pattern superimposed over rhythmic delta activity and periodic discharge was described for the first time in acute TBI. In rats, FPI increased high-amplitude spike incidence in the neocortex and, most expressed, in the ipsilateral hippocampus, induced hippocampal microgliosis and neuronal loss, ipsilateral dentate gyrus being most vulnerable, a week after TBI. Epileptiform spike incidence correlated with microglial cell density and neuronal loss in the ipsilateral hippocampus. Conclusion: Epileptiform activity is frequent in the acute period of TBI period and is associated with distant hippocampal damage on a microscopic level. This damage is probably involved in late consequences of TBI. The FPI model is suitable for exploring pathogenetic mechanisms of post-traumatic disorders.

Post-Traumatic Epilepsy after Sports-Related Concussion: A Case Report

Sports-related concussions (SRCs) are a public health concern across the United States, and they lead to neurological sequelae that can last long after the event itself. Concussive convulsions at the time of injury are common and rarely require additional workup or treatment. Post-traumatic epilepsy (PTE), however, is a rare phenomenon that can develop after traumatic brain injury and must be managed with adequate medical therapy. Herein we present the case of a 15-year-old football player who developed PTE after an SRC. This condition must be identified through proper education of sports clinicians and those involved in care and management of athletes.

Tumor Necrosis Factor-α, the Pathological Key to Post-Traumatic Epilepsy: A Comprehensive Systematic Review

Post-traumatic epilepsy (PTE) is one of the detrimental outcomes of traumatic brain injury (TBI), resulting in recurrent seizures that impact daily life. However, the pathological relationship between PTE and TBI remains unclear, and commonly prescribed antiepileptic drugs (AED) are ineffective against PTE. Fortunately, emerging research implicates neuroinflammation, particularly, tumor necrosis factor-α (TNF-α), as the key mediator for PTE development. Thus, this review aims to examine the available literature regarding the role of TNF-α in PTE pathology and, subsequently, evaluate TNF-α as a possible target for its treatment. A comprehensive literature search was conducted on four databases including PubMed, CINAHL, Embase, and Scopus. Articles with relevance in investigating TNF-α expression in PTE were considered in this review. Critical evaluation of four articles that met the inclusion criteria suggests a proportional relationship between TNF-α expression and seizure susceptibilit and that neutralization or suppression of TNF-α release results in reduced susceptibility to seizures. In conclusion, this review elucidates the importance of TNF-α expression in epileptogenesis postinjury and urges future research to focus more on clinical studies involving TNF-α, which may provide clearer insight into PTE prevention, therefore improving the lives of PTE patients.

Animal Models of Post-Traumatic Epilepsy

Traumatic brain injury is the leading cause of morbidity and mortality worldwide, with the incidence of post-traumatic epilepsy increasing with the severity of the head injury. Post-traumatic epilepsy (PTE) is defined as a recurrent seizure disorder secondary to trauma to the brain and has been described as one of the most devastating complications associated with TBI (Traumatic Brain Injury). The goal of this review is to characterize current animal models of PTE and provide succinct protocols for the development of each of the currently available animal models. The development of translational and effective animal models for post-traumatic epilepsy is critical in both elucidating the underlying pathophysiology associated with PTE and providing efficacious clinical breakthroughs in the management of PTE.

Neuroinflammation in Post-Traumatic Epilepsy: Pathophysiology and Tractable Therapeutic Targets

Epilepsy is a common chronic consequence of traumatic brain injury (TBI), contributing to increased morbidity and mortality for survivors. As post-traumatic epilepsy (PTE) is drug-resistant in at least one-third of patients, there is a clear need for novel therapeutic strategies to prevent epilepsy from developing after TBI, or to mitigate its severity. It has long been recognized that seizure activity is associated with a local immune response, characterized by the activation of microglia and astrocytes and the release of a plethora of pro-inflammatory cytokines and chemokines. More recently, increasing evidence also supports a causal role for neuroinflammation in seizure induction and propagation, acting both directly and indirectly on neurons to promote regional hyperexcitability. In this narrative review, we focus on key aspects of the neuroinflammatory response that have been implicated in epilepsy, with a particular focus on PTE. The contributions of glial cells, blood-derived leukocytes, and the blood–brain barrier will be explored, as well as pro- and anti-inflammatory mediators. While the neuroinflammatory response to TBI appears to be largely pro-epileptogenic, further research is needed to clearly demonstrate causal relationships. This research has the potential to unveil new drug targets for PTE, and identify immune-based biomarkers for improved epilepsy prediction.

A MACHINE LEARNING MODEL TO PREDICT SEIZURE SUSCEPTIBILITY FROM RESTING-STATE FMRI CONNECTIVITY

Traumatic brain injury (TBI) is a leading cause of disability globally. Many patients develop post-traumatic epilepsy, or recurrent seizures following TBI. In recent years, significant efforts have been made to identify biomarkers of epileptogenesis that may assist in preventing seizure occurrence by identifying high-risk patients. We present a novel method of assessing seizure susceptibility using data from 49 patients enrolled in the Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx). We employ a machine learning paradigm that utilizes a Random Forest classifier trained with resting-state functional magnetic resonance imaging (fMRI) data to predict seizure outcomes. Following 100 rounds of stratified cross-validation with 70% of resting state fMRI scans as the training set and 30% as the testing set, our model was found to assess seizure outcome in the testing set with 69% accuracy. To validate the method, we compared our results with classification by Support Vector Machines and Neural Network classifiers.

Extracellular Vesicles as Diagnostics and Therapeutics for Structural Epilepsies

Extracellular vesicles (EVs) are small vesicles involved in intercellular communication. Data is emerging that EVs and their cargo have potential as diagnostic biomarkers and treatments for brain diseases, including traumatic brain injury and epilepsy. Here, we summarize the current knowledge regarding changes in EV numbers and cargo in status epilepticus (SE) and traumatic brain injury (TBI), which are clinically significant etiologies for acquired epileptogenesis in animals and humans. We also review encouraging data, which suggests that EVs secreted by stem cells may serve as recovery-enhancing treatments for SE and TBI. Using Gene Set Enrichment Analysis, we show that brain EV-related transcripts are positively enriched in rodent models of epileptogenesis and epilepsy, and altered in response to anti-seizure drugs. These data suggest that EVs show promise as biomarkers, treatments and drug targets for epilepsy. In parallel to gathering conceptual knowledge, analytics platforms for the isolation and analysis of EV contents need to be further developed.

Variability with Astroglial Glutamate Transport Genetics Is Associated with Increased Risk for Post-Traumatic Seizures

Excitotoxicity contributes to epileptogenesis after severe traumatic brain injury (sTBI). Demographic and clinical risk factors for post-traumatic seizures (PTS) have been identified, but genetic risk remains largely unknown. Thus, we investigated whether genetic variation in astroglial glutamate transporter genes is associated with accelerated epileptogenesis and PTS risk after sTBI. Adults (n = 267) 18-75 years old were assessed over a three-year period post-TBI. Single nucleotide polymorphisms (SNPs) throughout the SLC1A2 and SLC1A3 genes were assayed. Kaplan-Meier estimates and log-rank statistics were used to compare seizure frequencies by genotype. Multivariate Cox proportional hazards regression was used to estimate hazard ratios (HRs) for genotypes significant in Kaplan-Meier analyses. Thirty-nine tagging SNPs were examined (SLC1A2: n = 21, SLC1A3: n = 18). PTS developed in 57 (21.4%) individuals. Of those with PTS, n = 20 (35.7%) had an immediate/early seizure within the first seven days, and n = 36 (64.3%) had a late seizure occurring between eight days and three years post-TBI. When adjusting for multiple comparisons, rs4869682 genotypes (SLC1A3, GG vs. T-carriers) were associated with time to first seizure (p = 0.003). Median time until first seizure was 20.4 days for individuals with a GG genotype and 44.8 days for T-carriers. After adjusting for covariates, rs4869682 GG-homozygotes had a 2.05 times increased PTS risk versus T-carriers (aHR = 2.08, 95% confidence interval: 1.20, 3.62, p = 0.009). Variation within SLC1A3 is associated with accelerated epileptogenesis and clinical PTS development after sTBI. Future studies should validate these findings and examine how genetic variation at rs4869682 may be a target for PTS prevention and treatment.

Neuroimaging of Subacute Brain Inflammation and Microstructural Changes Predicts Long-Term Functional Outcome after Experimental Traumatic Brain Injury

There is currently a lack of prognostic biomarkers to predict the different sequelae following traumatic brain injury (TBI). The present study investigated the hypothesis that subacute neuroinflammation and microstructural changes correlate with chronic TBI deficits. Rats were subjected to controlled cortical impact (CCI) injury, sham surgery, or skin incision (naïve). CCI-injured (n = 18) and sham-operated rats (n = 6) underwent positron emission tomography (PET) imaging with the translocator protein 18 kDa (TSPO) radioligand [¹⁸F]PBR111 and diffusion tensor imaging (DTI) in the subacute phase (≤3 weeks post-injury) to quantify inflammation and microstructural alterations. CCI-injured, sham-operated, and naïve rats (n = 8) underwent behavioral testing in the chronic phase (5.5-10 months post-injury): open field and sucrose preference tests, two one-week video-electroencephalogram (vEEG) monitoring periods, pentylenetetrazole (PTZ) seizure susceptibility tests, and a Morris water maze (MWM) test. In vivo imaging revealed pronounced neuroinflammation, decreased fractional anisotropy, and increased diffusivity in perilesional cortex and ipsilesional hippocampus of CCI-injured rats. Behavioral analysis revealed disinhibition, anhedonia, increased seizure susceptibility, and impaired learning in CCI-injured rats. Subacute TSPO expression and changes in DTI metrics significantly correlated with several chronic deficits (Pearson's |r| = 0.50-0.90). Certain specific PET and DTI parameters had good sensitivity and specificity (area under the receiver operator characteristic [ROC] curve = 0.85-1.00) to distinguish between TBI animals with and without particular behavioral deficits. Depending on the investigated behavioral deficit, PET or DTI data alone, or the combination, could very well predict the variability in functional outcome data (adjusted R² = 0.54-1.00). Taken together, both TSPO PET and DTI seem promising prognostic biomarkers to predict different chronic TBI sequelae.

The Effect of Keppra Prophylaxis on the Incidence of Early Onset, Post-traumatic Brain Injury Seizures

Objective: Traumatic brain injury (TBI) is a leading cause of long-term disability. Early onset post-traumatic seizures (PTS) after traumatic injury to the brain is a strong predictor of adverse outcomes in these patients. Our study investigates the role of Keppra in early PTS prophylaxis compared to no treatment, taking into account risk factors including injury severity, seizure history, and anti-epileptic drug (AED) use.

Methods: This was a retrospective cohort study based on patient chart data from January 2013 to January 2017 at a level one trauma center in the United States. A t-test was performed with P<0.05 as significant; we utilized a 95% confidence interval (CI) for our findings. Subgroup analysis was performed, with respect to the Glasgow Coma Scale (GCS) score (Group A: Mild GCS=13-15, Keppra N=135, Non-Keppra N=122; Group B: Moderate GCS=9-12, Keppra N=23, Non-Keppra N=19; Group C: Severe GCS= <8, Keppra N=69, Non-Keppra=35).

Results: Of 403 patients included in the study, 227 were given Keppra. Demographics between treatment groups were similar. Whole cohort analysis confirmed six patients with PTS, and no significant difference between groups (Keppra N=3, Non-Keppra N=3, OR=0.77, P=0.75, 95% CI=(0.154-3.87)). Subgroup analysis revealed reduction in seizure incidence in Keppra groups A (OR=0.18, P=0.27, 95% CI=(0.008-3.80)) and B (OR=0.82, P=0.92, 95% CI=(0.015-43.7)), but this reduction was not statistically significant. Those with the severe TBI in group C accounted for the majority of seizures (n=4, OR=1.52, P=0.71, 95% CI=(0.15-15.4)). 

Conclusion: Patients with more severe TBI suffered a higher incidence of early-onset post-traumatic seizures. Data of the cohort as a whole revealed a trend towards a lower seizure incidence in patients who were treated with Keppra prophylaxis. Despite this trend, the decrease in seizure incidence did not reach statistical significance.

Rapamycin provides anti-epileptogenic effect in a rat model of post-traumatic epilepsy via deactivation of mTOR signaling pathway

The mammalian target of rapamycin (mTOR) signaling pathway has attracted much attention in recent years. However, the contribution of mTOR activation to the development of post-traumatic epilepsy (PTE) remains largely unknown. The purpose of the present study was to investigate the activation of mTOR signaling in a rat model of FeCl₂-induced PTE, and to explore the potential effect of its specific inhibitor rapamycin. The results indicated that the expression levels of p-mTOR and p-P70S6K, the overactivation biomarkers of mTOR signaling, increased significantly in hippocampal and perilesional cortex following PTE induction. Notably, they were significantly decreased in the aformementioned brain regions following rapamycin treatment. Furthermore, the frequency and number of behavioral seizures and epileptic brain injury were also greatly reduced. These results suggest that hyperactivation of the mTOR signaling pathway is a crucial mechanism of PTE development, and it may be considered a novel therapeutic target for PTE treatment.

Biomarkers in traumatic brain injury (TBI): a review

Biomarkers can be broadly defined as qualitative or quantitative measurements that convey information on the physiopathological state of a subject at a certain time point or disease state. Biomarkers can indicate health, pathology, or response to treatment, including unwanted side effects. When used as outcomes in clinical trials, biomarkers act as surrogates or substitutes for clinically meaningful endpoints. Biomarkers of disease can be diagnostic (the identification of the nature and cause of a condition) or prognostic (predicting the likelihood of a person's survival or outcome of a disease). In addition, genetic biomarkers can be used to quantify the risk of developing a certain disease. In the specific case of traumatic brain injury, surrogate blood biomarkers of imaging can improve the standard of care and reduce the costs of diagnosis. In addition, a prognostic role for biomarkers has been suggested in the case of post-traumatic epilepsy. Given the extensive literature on clinical biomarkers, we will focus herein on biomarkers which are present in peripheral body fluids such as saliva and blood. In particular, blood biomarkers, such as glial fibrillary acidic protein and salivary/blood S100B, will be discussed together with the use of nucleic acids (eg, DNA) collected from peripheral cells.

Risk of post-traumatic epilepsy after severe head injury in patients with at least one seizure

BACKGROUND

To explore the incidence and risk factors, including type of seizures for post-traumatic epilepsy (PTE) after severe traumatic brain injury (TBI).

SUBJECTS AND METHODS

This was a retrospective follow-up study of patients discharged from Liaocheng People's Hospital between March 2011 and June 2015 with a diagnosis of post-traumatic seizures. Risk factors for PTE were evaluated in 68 inpatients by using Kaplan-Meier curves and the Cox model.

RESULTS

Complete clinical information was available for 68 patients. A total of 54 cases (79.4%) were diagnosed as presenting with PTE, occurring from 10 days to 179 months after severe TBI. Nineteen out of 54 cases (35.2%) had been defined as PTE within the first 6 months after the trauma, 17 cases (31.5%) within 7-12 months, 8 cases (14.8%) within 13-24 months, 2 cases (3.7%) within 25-36 months, and 8 cases (14.8%) within 37-179 months after the TBI. The Kaplan-Meier curves demonstrated that simple partial seizures, surgical treatment, and onset of seizures occurring within 6 months after injury were associated with PTE.

CONCLUSIONS

The Cox model indicated that, for patients aged >34 years at the time of injury, the PTE risk was 2.55 times greater than for those aged ≤34 years. In addition, simple partial seizures, surgical treatment and onset of seizures occurring within 6 months after injury were significant risk factors for the development of PTE.

Post-Traumatic, Drug-Resistant Epilepsy and Review of Seizure Control Outcomes from Blinded, Randomized Controlled Trials of Brain Stimulation Treatments for Drug-Resistant Epilepsy

Background: Many post-traumatic epilepsy (PTE) patients become resistant to medications. Nervous stimulation as a treatment for drug-resistant epilepsy (DRE) is an active area of clinical investigation.

Objective: To summarize methods, reported seizure control outcome measures, and adverse events from blinded, randomized control trials (RCTs) for selected invasive brain stimulation (IBS) and non-invasive brain stimulation (NIBS) treatment options in patients with DRE.

Methods: PubMed was searched for articles from 1995-2014, using search terms related to the topics of interest. Available relevant articles reporting the outcomes of interest were identified and data was extracted. Articles in the reference lists of relevant articles and clinicaltrials.gov were also referenced.

Results: Eleven articles were analyzed with a total of 795 patients identified. Studies showed that select nervous stimulation treatments significantly reduced seizure frequency in patients with DRE. 

Current and future diagnostic tools for traumatic brain injury: CT, conventional MRI, and diffusion tensor imaging

Brain imaging plays a key role in the assessment of traumatic brain injury. In this review, we present our perspectives on the use of computed tomography (CT), conventional magnetic resonance imaging (MRI), and newer advanced modalities such as diffusion tensor imaging. Specifically, we address assessment for immediately life-threatening intracranial lesions (noncontrast head CT), assessment of progression of intracranial lesions (noncontrast head CT), documenting intracranial abnormalities for medicolegal reasons (conventional MRI with blood-sensitive sequences), presurgical planning for post-traumatic epilepsy (high spatial resolution conventional MRI), early prognostic decision making (conventional MRI with diffusion-weighted imaging), prognostic assessment for rehabilitative planning (conventional MRI and possibly diffusion tensor imaging in the future), stratification of subjects and pharmacodynamic tracking of targeted therapies in clinical trials (specific MRI sequences or positron emission tomography (PET) ligands, e.g., diffusion tensor imaging for traumatic axonal injury). We would like to emphasize that all of these methods, especially the newer research approaches, require careful radiologic-pathologic validation for optimal interpretation. We have taken this approach in a mouse model of pericontusional traumatic axonal injury. We found that the extent of reduction in the diffusion tensor imaging parameter relative anisotropy directly correlated with the number of amyloid precursor protein (APP)-stained axonal varicosities (r(2)=0.81, p<0.0001, n=20 injured mice). Interestingly, however, the least severe contusional injuries did not result in APP-stained axonal varicosities, but did cause reduction in relative anisotropy. Clearly, both the imaging assessments and the pathologic assessments will require iterative refinement.

Transition from Initial Hypoactivity to Hyperactivity in Cortical Layer V Pyramidal Neurons after Traumatic Brain Injury In Vivo

Traumatic brain injury (TBI) often results in structural damage and a loss of neurons that is commonly accompanied by early changes in neuronal electrical activity. Loss of neuronal activity has been hypothesized to contribute to post-traumatic epileptogenesis through the regulation of homeostatic plasticity. The existence of activity loss in cortical neurons after TBI and its subsequent transition into hyperactivity over time is not well characterized, however, particularly in models of TBI in vivo. In the current study, changes in neuronal activity in the primary motor cortex after moderate controlled cortical impact (CCI) in mice were studied using a single-unit recording technique in vivo. Recordings were made at different time points after CCI from cortical layer V pyramidal neurons that were within 1-2 mm from the anterior edge of the injured foci. Within 1-4 h after CCI, the frequency of spontaneous single-unit activity depressed significantly, with the mean firing frequency decreasing from 2.59 ± 0.18 Hz in the sham group to 1.05 ± 0.20 Hz of the injured group. The firing frequencies recovered to the normal level at 1 day and 7 days post-CCI, but became significantly higher at 3 days and 14 days post-CCI. The results suggest that TBI caused initial loss of activity in neurons of the perilesional cortical region, which was followed by compensatory recovery and enhancement of activity. These time-dependent changes in neuronal activity may contribute to the development of hyperexcitability through homeostatic activity regulation.