Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis

Surgical Considerations of Intractable Mesial Temporal Lobe Epilepsy

Surgery of temporal lobe epilepsy is the best opportunity for seizure freedom in medically intractable patients. The surgical approach has evolved to recognize the paramount importance of the mesial temporal structures in the majority of patients with temporal lobe epilepsy who have a seizure origin in the mesial temporal structures. For those individuals with medically intractable mesial temporal lobe epilepsy, a selective amygdalohippocampectomy surgery can be done that provides an excellent opportunity for seizure freedom and limits the resection to temporal lobe structures primarily involved in seizure genesis.

Drug-resistant epilepsy development following stem cell transplant and cyclosporine neurotoxicity induced seizures: Case report in an adult and analysis of reported cases in the literature

Introduction

Drug-resistant epilepsy (DRE) occurs in 20–30% of all patients who develop epilepsy and can occur from diverse causes. Cyclosporine-A (CSA) is an immunosuppressive drug utilized to prevent graft-versus-host disease (GvHD) in transplant patients and is known to cause neurotoxicity, including seizures. In some cases, however, patients can develop DRE. Only a limited number of cases have been reported in which DRE has developed after CSA exposure — all in children. Here we present a rare case of an adult developing DRE after post-transplant CSA neurotoxicity. In addition, we provide a comprehensive review and analysis of all reported cases in the literature.

Case report

A 29-year-old man with Non-Hodgkin's Lymphoma underwent an allogenic hematopoietic stem cell transplant and experienced a CSA-induced seizure at 7.5 months' post-transplant. The patient was discontinued on CSA and began a low dose tacrolimus regimen. At 33 months' post-transplant, he had seizure recurrence and developed DRE. Imaging revealed right mesial temporal sclerosis (MTS) and video EEG localized ictal activity to the right anterior temporal lobe. He was successfully treated with a right anterior temporal lobectomy and amygdalohippocampectomy.

Literature review

Seven peer-reviewed studies described 15 patients who underwent transplantation with post-transplant CSA administration and subsequently developed DRE following an initial CSA-induced seizure. All 15 patients were children suggesting that young age is a risk factor for DRE after CSA-induced seizures. Initial CSA-induced seizures occurred at an average of 1.6 ± 1.1 months after transplant and seizure recurrence 9.2 ± 8.0 months after transplant. All reported CSA routes of administration (n = 6) were intravenous and 7 of 9 (78%) reported CSA blood levels above the therapeutic range. The incidence of MTS (40%) in these 15 patients was significantly higher than the incidence in the general DRE population (24%) and was most effectively treated via epilepsy surgery.

Conclusions

The use of cyclosporine for GvHD prophylaxis and treatment following transplantation may cause seizures and be associated with DRE. Although discontinuation and dose decrease of CSA often reverse adverse neurological events, initial CSA-induced seizures may be associated with MTS that and subsequent greater risk of DRE development.

Depressive disorders in patients with pharmaco-resistant mesial temporal lobe epilepsy

Objectives To assess depressive disorders in patients with mesial temporal lobe epilepsy (MTLE) refractory to medical treatment. Methods Adult patients with refractory MTLE completed two questionnaires (Mini International Neuropsychiatric Interview (MINI) and the Beck Depression Inventory (BDI) had a semi-structured psychiatric interview and a high resolution MRI scan. For complete neuropsychiatric diagnosis, as per International Classification of Diseases (ICD-10), the results were combined with clinical history and additional information from the patients' family. Results Of the 40 patients identified for this case series study which took place from 2008-2012, 31 (77.5%) had a depressive disorder: 14 had dysthymia, 11 had recurrent depressive disorder and 6 had bipolar disorder. Of the nine patients without a firm diagnosis of mood disorder, seven had isolated symptoms of depression or anxiety and two presented with mixed depression/anxiety symptoms. Only 8/31 (25.8%) patients were receiving antidepressant treatment. There was no association between BDI scores and seizure frequency. No significant difference was found between patients with and without depression and the presence or laterality of HA. Conclusions Depressive disorders are common, underdiagnosed and undertreated in patients with refractory MTLE.

Acetazolamide Suppresses Multi-Drug Resistance-Related Protein 1 and P-Glycoprotein Expression by Inhibiting Aquaporins Expression in a Mesial Temporal Epilepsy Rat Model

Background

Mesial temporal epilepsy (MTLE) is the most common type of focal epilepsy in adults, and is often drug-resistant. This study investigated the effects of aquaporins (AQP) inhibitor on multi-drug-resistant protein expression in an MTLE rat model.

Material/Methods

The MTLE rat model was established by injecting pilocarpine into rats. The MTLE rats were divided into an MTLE-6 h group, an MTLE-12 h group, and an MTLE-24 h group, together with a normal saline group (NS), to examine the AQP4 expression by using Western blot assay and immunohistochemistry assay. The other 18 MTLE model rats were used to observe the effects of the AQP4 inhibitor, acetazolamide, on the multi-drug-resistant protein 1 (MRP1) and P-glycoprotein (Pgp) by using Western blot and immunohistochemistry assays, respectively.

Results

AQP4 expression was enhanced in hippocampal tissues of MTLE model rats compared to NS rats (P<0.05). More positively stained AQP4 was discovered in hippocampal tissues of MTLE model rats. AQP4 inhibitor significantly decreased multi-drug-resistant protein MRP1 and Pgp expression in the AQP4 inhibitor Interfere group and the AQP4 inhibitor Therapy group compared to the TMLE model group (P<0.05).

Conclusions

The present findings confirm that the AQP4 inhibitor, acetazolamide, effectively inhibits the multi-drug-resistant protein, MRP1, and Pgp, in the MTLE rat model.

A Hierarchical Bayesian Model for the Identification of PET Markers Associated to the Prediction of Surgical Outcome after Anterior Temporal Lobe Resection

We develop an integrative Bayesian predictive modeling framework that identifies individual pathological brain states based on the selection of fluoro-deoxyglucose positron emission tomography (PET) imaging biomarkers and evaluates the association of those states with a clinical outcome. We consider data from a study on temporal lobe epilepsy (TLE) patients who subsequently underwent anterior temporal lobe resection. Our modeling framework looks at the observed profiles of regional glucose metabolism in PET as the phenotypic manifestation of a latent individual pathologic state, which is assumed to vary across the population. The modeling strategy we adopt allows the identification of patient subgroups characterized by latent pathologies differentially associated to the clinical outcome of interest. It also identifies imaging biomarkers characterizing the pathological states of the subjects. In the data application, we identify a subgroup of TLE patients at high risk for post-surgical seizure recurrence after anterior temporal lobe resection, together with a set of discriminatory brain regions that can be used to distinguish the latent subgroups. We show that the proposed method achieves high cross-validated accuracy in predicting post-surgical seizure recurrence.

Electro-clinical criteria and surgical outcome: Is there a difference between mesial and lesional temporal lobe epilepsy?

OBJECTIVES

Mesial temporal lobe epilepsy syndrome (MTLE) with specific electrophysiological and clinical characteristics and hippocampal sclerosis (HS) on MRI is considered the prototype of a syndrome with good surgical prognosis. Ictal onset zones in MTLE have been found to extend outside the hippocampus and neocortical seizures often involve mesial structures. It can, thus, be questioned whether MTLE with HS is different from lesional temporal epilepsies with respect to electro-clinical characteristics and surgical prognosis. We assessed whether MTLE with HS is distinguishable from lesional TLE and which criteria determine surgical outcome.

METHODS

People in a retrospective cohort of 389 individuals with MRI abnormalities who underwent temporal lobectomy, were divided into "HS only" or "lesional" TLEs. Twenty-six presented with dual pathology and were excluded from further analysis. We compared surgical outcome and electro-clinical characteristics.

RESULTS

Over half (61%) had "HS only." Four electro-clinical characteristics (age at epilepsy onset, febrile seizures, memory dysfunction and contralateral dystonic posturing) distinguished "HS only" from "lesional" TLE, but there was considerable overlap. Seizure freedom 2 years after surgery (Engel class 1) was similar: 67% ("HS only") vs 69% ("lesional" TLE). Neither presence of HS nor electro-clinical criteria was associated with surgical outcome.

CONCLUSIONS

Despite small differences in electrophysiological and clinical characteristics between MTLE with HS and lesional TLE, surgical outcomes are similar, indicating that aetiology seems irrelevant in the referral for temporal surgery.

Investigation of anti-neuronal antibodies in status epilepticus of unknown etiology: a prospective study

There have been recent reports of antibody-mediated status epilepticus. The objective of our study was to investigate the prevalence of neuronal autoantibodies in patients with status epilepticus (SE) with unresolved etiology. The presence of neuronal autoantibodies was investigated prospectively in adult patients with SE who presented to our clinic between February 2012 and December 2013 with unresolved etiology. Clinical and electrophysiologic features of seropositive patients were recorded. Also, seronegative and seropositive patient groups were compared in terms of demographic and clinical features, treatment responses, and outcomes. Neuronal antibodies against N-methyl-D-aspartate receptor (NMDA-R) were positive in 2 patients, against glycine receptor (Gly-R) in 2 patients, and against gamma-aminobutyric acid-A receptor [GABA(A)R] in 1 patient, which constituted a total of 5 (22.7%) of 22 patients with SE with unidentified etiology. One of three patients with systemic tumors was positive for GABA(A)R antibody. Four patients had a short epilepsy duration, while one of the NMDA-R antibody-positive patients had chronic epilepsy and double cortex finding in MRI. There was no significant difference between seropositive and seronegative patient groups in terms of demographic and clinical features, treatment responses, and outcomes. Neuronal antibodies are found in a sizeable portion of de novo SE patients, who are potential candidates of autoimmune encephalitis. Alternatively, these antibodies may presumably also emerge in SE patients with a chronic epilepsy history as an epiphenomenon. Further research is required to make the distinction between these two different antibody formation mechanisms.

Amygdalohippocampotomy for mesial temporal lobe sclerosis: Epilepsy outcome 5 years after surgery

BACKGROUND

The goal of the present study is the evaluation of the long-term clinical outcome of epilepsy in patients with mesial temporal lobe sclerosis (MTLS) submitted to amygdalohippocampotomy (AHCo). AHCo consists of the lateral ablation of the amygdala and the peri-hippocampal disconnection instead of amygdalohippocampectomy (AHC), which involves the removal of both structures. We previously reported the short-term results of AHCo, so we here present the long-term results (> 5 years of follow-up) of the patients operated on with AHCo.

METHOD

Since 2007, 35 patients (22 females) aged 20-61 years (mean: 42 years) were operated on with the AHCo technique, 17 patients on the left side and 18 on the right. Of these patients, 21 (14 females) have been followed up > 5 years (5 to 7.5 years, mean 6.5 years). We compare the present results with those observed shortly after surgery and with the patients operated on with AHC.

FINDINGS

In all 21 cases, the diagnosis was mesial temporal lobe sclerosis (histology confirmed in 20), 11 on the left side and 10 on the right. Epilepsy results after 5 years were good/very good in 18 patients (85.7%), with Engel class IA-B in 15 (71.4%) and II in 3 (14.3%), and bad in 3 patients, with Engel Class III in 2 (9.5%) and class IV in 1 (4.8%). Concerning morbidity, one patient had hemiparesis (hypertensive capsular hemorrhage 24 h after surgery), two verbal memory worsening, two quadrantanopia and three late depression that was reversed with medication. Comparatively, the AHC long-term results were 87% Engel class I, 8% Engel class II and 5% Engel class III-IV. The morbidity was equally small.

CONCLUSIONS

The good/very good results of AHCo 5 years after surgery are 86%, which is not distinct from the AHC results. So AHCo seems to be effective and potentially safer than AHC in long-term follow-up.

Parahippocampal Involvement in Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis: A Proof of Concept from Memory-Guided Saccades

Objective

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) may involve extrahippocampal areas of structural damage and dysfunction. The accuracy of medium-term spatial memory can be tested by memory-guided saccades (MGS) to evaluate a functional impairment of the parahippocampal cortex (PHC), while voxel-based morphometry (VBM) analysis can be used to detect a structural damage of the latter region.

Methods

MGS with 3- and 30-s memorization delays were compared between 7 patients affected by right MTLE-HS (r-MTLE-HS), 6 patients affected by left MTLE-HS, and 13 healthy controls. The same subjects underwent brain MRI for a VBM analysis. Correlation analysis was performed between the results of VBM and MGS and with patients’ clinical data.

Results

Right MTLE-HS patients showed impaired accuracy of leftward MGS with a 30-s memorization delay; their gray-matter volume was reduced in the right hippocampus and inferior temporal gyrus, and bilaterally in the cerebellum. Left MTLE-HS patients had normal MGS accuracy; their gray-matter volume was reduced in the left hippocampus, in the right-inferior temporal gyrus and corpus callosus, and bilaterally in the insular cortex and in the cerebellum. The difference between right and left parahippocampal volumes correlated with MGS accuracy, while right and left hippocampal volumes did not. Hippocampal and parahippocampal volume did not correlate with clinical variables such as febrile seizures, age at disease onset, disease duration, and seizure frequency.

Conclusion

MGS abnormalities suggested the functional involvement of the right PHC in patients with r-MTLE-HS, supporting a right lateralization of spatial memory control and showing a relation between functional impairment and degree of atrophy.

Transcriptome and in Vitro Differentiation Profile of Human Embryonic Stem Cell Derived NKX2.1-Positive Neural Progenitors

The generation of inhibitory interneuron progenitors from human embryonic stem cells (ESCs) is of great interest due to their potential use in transplantation therapies designed to treat central nervous system disorders. The medial ganglionic eminence (MGE) is a transient embryonic structure in the ventral telencephalon that is a major source of cortical GABAergic inhibitory interneuron progenitors. These progenitors migrate tangentially to sites in the cortex and differentiate into a variety of interneuron subtypes, forming local synaptic connections with excitatory projection neurons to modulate activity of the cortical circuitry. The homeobox domain-containing transcription factor NKX2.1 is highly expressed in the MGE and pre-optic area of the ventral subpallium and is essential for specifying cortical interneuron fate. Using a combination of growth factor agonists and antagonists to specify ventral telencephalic fates, we previously optimized a protocol for the efficient generation of NKX2.1-positive MGE-like neural progenitors from human ESCs. To establish their identity, we now characterize the transcriptome of these MGE-like neural progenitors using RNA sequencing and demonstrate the capacity of these cells to differentiate into inhibitory interneurons in vitro using a neuron-astrocyte co-culture system. These data provide information on the potential origin of interneurons in the human brain.

Pharmacoresistance with newer anti-epileptic drugs in mesial temporal lobe epilepsy with hippocampal sclerosis

This study aims to evaluate the overall prognosis, prognostic factors, and efficacy of treatment in patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) who have access to third generation anti-epileptic drugs but not to epilepsy surgery. Eighty-five MTLE-HS patients were retrospectively placed into a seizure-free (seizure-free for >1year) or drug-resistant group, and the two groups were compared on the basis of age, sex, age at onset of seizures, duration of epilepsy, side of lesion, handedness, EEG findings, history of CNS infection, history of febrile convulsions, history of head trauma, history of cognitive impairment, family history of seizures, number of current anti-epileptic drugs (AEDs), total number of AED trials, and presence of individual AEDs. Only 24.7% of MTLE-HS patients had achieved seizure freedom for >1 year. Poor prognosis and drug-resistance were associated with younger age at onset of seizures (p=0.002), longer duration of epilepsy (p=0.018), greater number of current AEDs (p<0.001), and greater total number of AED trials (p<0.001). In addition, regimens with newer AEDs had no greater efficacy than regimens with older AEDs. Most medically managed MTLE-HS patients do not achieve seizure freedom despite multiple AED trials, and treatment with third generation AEDs should not preclude evaluation for epilepsy surgery.

Establishment of a rhesus monkey model of chronic temporal lobe epilepsy using repetitive unilateral intra-amygdala kainic acid injections

OBJECTIVE

Temporal lobe epilepsy (TLE) is a common type of acquired epilepsy refractory to medical treatment. As such, establishing animal models of this disease is critical to developing new and effective treatment modalities. Because of their small head size, rodents are not suitable for comprehensive electroencephalography (EEG) evaluation via scalp or subdural electrodes. Therefore, a larger primate model that closely recapitulates signs of TLE is needed; here we describe a rhesus monkey model resembling chronic TLE.

METHODS

Eight monkeys were divided into two groups: kainic acid (KA) group (n=6) and saline control group (n=2). Intra-amygdala KA injections were performed biweekly via an Ommaya device until obvious epileptiform discharges were recorded. Video-EEG recording was conducted intermittently throughout the experiment using both scalp and subdural electrodes. Brains were then analyzed for Nissl and glial fibrillary acid protein (GFAP) immunostaining.

RESULTS

After 2-4 injections of KA (approximately 1.2-2.4mg, 0.12-0.24mg/kg), interictal epileptiform discharges (IEDs) were recorded in all KA-treated animals. Spontaneous recurrent seizures (SRSs) accompanied by symptoms mimicking temporal lobe absence (undetectable without EEG recording), but few mild motor signs, were recorded in 66.7% (four of six) KA-treated animals. Both IEDs and seizures indicated a primary epileptic zone in the right temporal region and contralateral discharges were later detected. Segmental pyramidal cell loss and gliosis were detected in the brain of a KA-treated monkey.

CONCLUSIONS

Through a modified protocol of unilateral repetitive intra-amygdala KA injections, a rhesus monkey model with similar behavioral and brain electrical features as TLE was developed.

MicroRNA and mesial temporal lobe epilepsy with hippocampal sclerosis: Whole miRNome profiling of human hippocampus

OBJECTIVE

Mesial temporal lobe epilepsy (mTLE) is a severe neurological disorder characterized by recurrent seizures. mTLE is frequently accompanied by neurodegeneration in the hippocampus resulting in hippocampal sclerosis (HS), the most common morphological correlate of drug resistance in mTLE patients. Incomplete knowledge of pathological changes in mTLE+HS complicates its therapy. The pathological mechanism underlying mTLE+HS may involve abnormal gene expression regulation, including posttranscriptional networks involving microRNAs (miRNAs). miRNA expression deregulation has been reported in various disorders, including epilepsy. However, the miRNA profile of mTLE+HS is not completely known and needs to be addressed.

METHODS

Here, we have focused on hippocampal miRNA profiling in 33 mTLE+HS patients and nine postmortem controls to reveal abnormally expressed miRNAs. In this study, we significantly reduced technology-related bias (the most common source of false positivity in miRNA profiling data) by combining two different miRNA profiling methods, namely next generation sequencing and miRNA-specific quantitative real-time polymerase chain reaction.

RESULTS

These methods combined have identified and validated 20 miRNAs with altered expression in the human epileptic hippocampus; 19 miRNAs were up-regulated and one down-regulated in mTLE+HS patients. Nine of these miRNAs have not been previously associated with epilepsy, and 19 aberrantly expressed miRNAs potentially regulate the targets and pathways linked with epilepsy (such as potassium channels, γ-aminobutyric acid, neurotrophin signaling, and axon guidance).

SIGNIFICANCE

This study extends current knowledge of miRNA-mediated gene expression regulation in mTLE+HS by identifying miRNAs with altered expression in mTLE+HS, including nine novel abnormally expressed miRNAs and their putative targets. These observations further encourage the potential of microRNA-based biomarkers or therapies.

Knowledge and Awareness of Epilepsy Surgery among Medical Students

Background and Purpose

Surgery is an alternative treatment of drug-resistant epilepsy. Positive attitude of medical personnel towards epilepsy surgery is essential. This study assessed general knowledge of and attitude towards epilepsy surgery among medical students. The aim of this study was to assess general knowledge of and attitude towards epilepsy surgery among medical students.

Methods

Questionnaire was distributed to medical students. Questionnaire consisted of two questions of general knowledge of drug-resistant epilepsy, questions of students’ attitude towards epilepsy surgery and questions of referral of patients. The Chi-square test was utilized.

Results

The terms “drug-resistant epilepsy” and “mesial temporal sclerosis” were known in 72.3 and 14.2 percent, respectively. Awareness and support of epilepsy surgery were recorded in 74.5 and 48.9 percent, respectively. A drug resistant patient would have been referred to a qualified centre in 19.4 percent. General knowledge and awareness of epilepsy surgery were better in higher levels of study (p < 0.001).

Conclusions

Medical students have a positive attitude towards epilepsy surgery. Students are aware of drug resistance in epilepsy. Knowledge and awareness are better among students in higher levels, after neurology is introduced to the curriculum. We conclude that highlighting the importance of epilepsy surgery should be continued. Moreover, additional educational effort should be invested in expressing the importance of efficient referral of a patient to a qualified centre.

Early tissue damage and microstructural reorganization predict disease severity in experimental epilepsy

Mesial temporal lobe epilepsy (mTLE) is the most common focal epilepsy in adults and is often refractory to medication. So far, resection of the epileptogenic focus represents the only curative therapy. It is unknown whether pathological processes preceding epilepsy onset are indicators of later disease severity. Using longitudinal multi-modal MRI, we monitored hippocampal injury and tissue reorganization during epileptogenesis in a mouse mTLE model. The prognostic value of MRI biomarkers was assessed by retrospective correlations with pathological hallmarks Here, we show for the first time that the extent of early hippocampal neurodegeneration and progressive microstructural changes in the dentate gyrus translate to the severity of hippocampal sclerosis and seizure burden in chronic epilepsy. Moreover, we demonstrate that structural MRI biomarkers reflect the extent of sclerosis in human hippocampi. Our findings may allow an early prognosis of disease severity in mTLE before its first clinical manifestations, thus expanding the therapeutic window.

Seizure severity-dependent selective vulnerability of the granule cell layer and aberrant neurogenesis in the rat hippocampus

The pilocarpine-induced status epilepticus rodent model has been commonly used to analyze the mechanisms of human temporal lobe epilepsy. Recent studies using this model have demonstrated that epileptic seizures lead to increased adult neurogenesis of the dentate granule cells, and cause abnormal cellular organization in dentate neuronal circuits. In this study, we examined these structural changes in rats with seizures of varying severity. In rats with frequent severe seizures, we found a clear loss of Prox1 and NeuN expression in the dentate granule cell layer (GCL), which was confined mainly to the suprapyramidal blade of the GCL at the septal and middle regions of the septotemporal axis of the hippocampus. In the damaged suprapyramidal region, the number of immature neurons in the subgranular zone was markedly reduced. In contrast, in rats with less frequent severe seizures, there was almost no loss of Prox1 and NeuN expression, and the number of immature neurons was increased. In rats with no or slight loss of Prox1 expression in the GCL, ectopic immature neurons were detected in the molecular layer of the suprapyramidal blade in addition to the hilus, and formed chainlike aggregated structures along the blood vessels up to the hippocampal fissure, suggesting that newly generated neurons migrate at least partially along blood vessels to the hippocampal fissure. These results suggest that seizures of different severity cause different effects on GCL damage, neurogenesis, and the migration of new neurons, and that these structural changes are selective to subdivisions of the GCL and the septotemporal axis of the hippocampus.

Immunogenetic predisposing factors for mesial temporal lobe epilepsy with hippocampal sclerosis

PURPOSE

Neuroinflammation appears as an important epileptogenic mechanism. Experimental and clinical studies have demonstrated an upregulation of pro-inflammatory cytokines such as IL-1β and TNF-α, in mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Expression of these cytokines can be modulated by polymorphisms such as rs16944 and rs1800629, respectively, both of which have been associated with febrile seizures (FS) and MTLE-HS development. The human leukocyte antigen (HLA) system has also been implicated in diverse epileptic entities, suggesting a variable role of this system in epilepsy. Our aim was to analyse the association between immunogenetic factors and MTLE-HS development. For that rs16944 (-511 T>C, IL-1β), rs1800629 (-308 G>A, TNF-α) polymorphisms and HLA-DRB1 locus were genotyped in a Portuguese Population.

METHODS

We studied 196 MTLE-HS patients (108 females, 88 males, 44.7 ± 12.0 years, age of onset = 13.6 ± 10.3 years, 104 with FS antecedents) and 282 healthy controls in a case-control study.

RESULTS

The frequency of rs16944 TT genotype was higher in MTLE-HS patients compared to controls (14.9% in MTLE-HS vs. 7.7% in controls, p = 0.021, OR [95% CI] = 2.20 [1.13-4.30]). This association was independent of FS antecedents. No association was observed between rs1800629 genotypes or HLA-DRB1 alleles and MTLE-HS susceptibility. Also, no correlation was observed between the studied polymorphisms and disease age of onset.

CONCLUSION

The rs16944 TT genotype is associated with MTLE-HS development what may be explained by the higher IL-1β levels produced by this genotype. High IL-1β levels may have neurotoxic effects or imbalance neurotransmission leading to seizures.

Automated volumetry of hippocampus is useful to confirm unilateral mesial temporal sclerosis in patients with radiologically positive findings

Background and purpose We evaluated two methods to identify mesial temporal sclerosis (MTS): visual inspection by experienced epilepsy neuroradiologists based on structural magnetic resonance imaging sequences and automated hippocampal volumetry provided by a processing pipeline based on the FMRIB Software Library. Methods This retrospective study included patients from the epilepsy monitoring unit database of our institution. All patients underwent brain magnetic resonance imaging in 1.5T and 3T scanners with protocols that included thin coronal T2, T1 and fluid-attenuated inversion recovery and isometric T1 acquisitions. Two neuroradiologists with experience in epilepsy and blinded to clinical data evaluated magnetic resonance images for the diagnosis of MTS. The diagnosis of MTS based on an automated method included the calculation of a volumetric asymmetry index between the two hippocampi of each patient and a threshold value to define the presence of MTS obtained through statistical tests (receiver operating characteristics curve). Hippocampi were segmented for volumetric quantification using the FIRST tool and fslstats from the FMRIB Software Library. Results The final cohort included 19 patients with unilateral MTS (14 left side): 14 women and a mean age of 43.4 ± 10.4 years. Neuroradiologists had a sensitivity of 100% and specificity of 73.3% to detect MTS (gold standard, k = 0.755). Automated hippocampal volumetry had a sensitivity of 84.2% and specificity of 86.7% (k = 0.704). Combined, these methods had a sensitivity of 84.2% and a specificity of 100% (k = 0.825). Conclusions Automated volumetry of the hippocampus could play an important role in temporal lobe epilepsy evaluation, namely on confirmation of unilateral MTS diagnosis in patients with radiological suggestive findings.

Novel therapeutic approaches for disease-modification of epileptogenesis for curing epilepsy

This article describes the recent advances in epileptogenesis and novel therapeutic approaches for the prevention of epilepsy, with a special emphasis on the pharmacological basis of disease-modification of epileptogenesis for curing epilepsy. Here we assess animal studies and human clinical trials of epilepsy spanning 1982-2016. Epilepsy arises from a number of neuronal factors that trigger epileptogenesis, which is the process by which a brain shifts from a normal physiologic state to an epileptic condition. The events precipitating these changes can be of diverse origin, including traumatic brain injury, cerebrovascular damage, infections, chemical neurotoxicity, and emergency seizure conditions such as status epilepticus. Expectedly, the molecular and system mechanisms responsible for epileptogenesis are not well defined or understood. To date, there is no approved therapy for the prevention of epilepsy. Epigenetic dysregulation, neuroinflammation, and neurodegeneration appear to trigger epileptogenesis. Targeted drugs are being identified that can truly prevent the development of epilepsy in at-risk people. The promising agents include rapamycin, COX-2 inhibitors, TRK inhibitors, epigenetic modulators, JAK-STAT inhibitors, and neurosteroids. Recent evidence suggests that neurosteroids may play a role in modulating epileptogenesis. A number of promising drugs are under investigation for the prevention or modification of epileptogenesis to halt the development of epilepsy. Some drugs in development appear rational for preventing epilepsy because they target the initial trigger or related signaling pathways as the brain becomes progressively more prone to seizures. Additional research into the target validity and clinical investigation is essential to make new frontiers in curing epilepsy.

Ginkgo biloba L. attenuates spontaneous recurrent seizures and associated neurological conditions in lithium-pilocarpine rat model of temporal lobe epilepsy through inhibition of mammalian target of rapamycin pathway hyperactivation

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. (Ginkgoaceae) has been widely used in traditional medicine for variety of neurological conditions particularly behavioral and memory impairments.

AIM OF THE STUDY

The present study was envisaged to explore the effect of a standardized fraction of Ginkgo biloba leaves (GBbf) in rat model of lithium-pilocarpine induced spontaneous recurrent seizures, and associated behavioral impairments and cognitive deficit.

MATERIALS AND METHODS

Rats showing appearance of spontaneous recurrent seizures following lithium pilocarpine (LiPc)-induced status epilepticus (SE) were treated with different doses of GBbf or vehicle for subsequent 4 weeks. The severity of seizures and aggression in rats were scored following treatment with GBbf. Further, open field, forced swim, novel object recognition and Morris water maze tests were conducted. Histopathological, protein levels and gene expression studies were performed in the isolated brains.

RESULTS

Treatment with GBbf reduced seizure severity score and aggression in epileptic animals. Improved spatial cognitive functions and recognition memory, along with reduction in anxiety-like behavior were also observed in the treated animals. Histopathological examination by Nissl staining showed reduction in neuronal damage in the hippocampal pyramidal layer. The dentate gyrus and Cornu Ammonis 3 regions of the hippocampus showed reduction in mossy fiber sprouting. GBbf treatment attenuated ribosomal S6 and pS6 proteins, and hippocampal mTOR, Rps6 and Rps6kb1 mRNA levels.

CONCLUSIONS

The results of present study concluded that GBbf treatment suppressed lithium-pilocarpine induced spontaneous recurrent seizures severity and incidence with improved cognitive functions, reduced anxiety-like behavior and aggression. The effect was found to be due to inhibition of mTOR pathway hyperactivation linked with recurrent seizures.

Weather as a risk factor for epileptic seizures: A case-crossover study

OBJECTIVE

Most epileptic seizures occur unexpectedly and independently of known risk factors. We aimed to evaluate the clinical significance of patients' perception that weather is a risk factor for epileptic seizures.

METHODS

Using a hospital-based, bidirectional case-crossover study, 604 adult patients admitted to a large university hospital in Central Germany for an unprovoked epileptic seizure between 2003 and 2010 were recruited. The effect of atmospheric pressure, relative air humidity, and ambient temperature on the onset of epileptic seizures under temperate climate conditions was estimated.

RESULTS

We found a close-to-linear negative correlation between atmospheric pressure and seizure risk. For every 10.7 hPa lower atmospheric pressure, seizure risk increased in the entire study population by 14% (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.01-1.28). In patients with less severe epilepsy treated with one antiepileptic medication, seizure risk increased by 36% (1.36, 1.09-1.67). A high relative air humidity of >80% increased seizure risk in the entire study population by up to 48% (OR 1.48, 95% CI 1.11-1.96) 3 days after exposure in a J-shaped association. High ambient temperatures of >20°C decreased seizure risk by 46% in the overall study population (OR 0.54, 95% CI 0.32-0.90) and in subgroups, with the greatest effects observed in male patients (OR 0.33, 95% CI 0.14-0.74).

SIGNIFICANCE

Low atmospheric pressure and high relative air humidity are associated with an increased risk for epileptic seizures, whereas high ambient temperatures seem to decrease seizure risk. Weather-dependent seizure risk may be accentuated in patients with less severe epilepsy. Our results require further replication across different climate regions and cohorts before reliable clinical recommendations can be made.

NMDAR-independent hippocampal long-term depression impairment after status epilepticus in a lithium-pilocarpine model of temporal lobe epilepsy

Temporal lobe epilepsy is usually associated with cognitive decline and memory deficits. Despite numerous existing studies on various animal models, the mechanisms of these deficits remain largely unclear. A specific form of long-term synaptic efficacy changes-long-term depression (LTD)-is thought to play an important role in memory formation and learning. However, extremely little is known about the possible alteration of LTD induction and dynamics after a status epilepticus (SE). In this work, we investigated the acute and delayed effects of lithium-pilocarpine-induced SE on NMDAR-dependent and NMDAR-independent hippocampal LTD in vitro. We found that SE affected the NMDAR-dependent and NMDAR-independent forms of LTD in different manners. The NMDAR-dependent form of LTD was almost intact 3 days after SE, but it switched from a predominantly presynaptic to a more postsynaptic locus of expression. In contrast, the NMDAR-independent LTD in the hippocampal Schaffer collaterals-CA1 synapses was fully abolished 3 days after SE. Our results emphasize the role of non-NMDA-dependent synaptic plasticity changes in the processes of epileptogenesis and the potential for therapy development.

Is 'burned-out hippocampus' syndrome a distinct electro-clinical variant of MTLE-HS syndrome?

AIM

To study the clinical, electrophysiological and imaging characteristics of patients with unilateral mesial temporal lobe epilepsy (MTLE) with contralateral ictal onset on scalp EEG, viz. 'burned-out hippocampus' syndrome (MTLE-BHS).

METHODS

MTLE-BHS was defined as TLE with unilateral hippocampal sclerosis (HS) without any dual pathology on MRI and contralateral ictal onset on scalp EEG, unlike in classical hippocampal sclerosis (HS). Consecutive "MTLE-BHS" patients evaluated at our Centre for Comprehensive Epilepsy Care from January 2005 to July 2014 were studied. Twenty-five cases of classic MTLE-HS operated during the same period were also analyzed for comparison.

RESULTS

Seventeen patients were diagnosed to have MTLE-BHS. Mean age of seizure onset was 9.5±7.7years and the mean duration of epilepsy was18.2±7.3years. Epigastric aura was more common in MTLE-HS and fear, secondary generalized seizures and temporal polar changes on MRI were more prevalent in the MTLE-BHS subgroup. In the latter group, five (29%) exhibited seizure semiology and 2 (12%) had interictal discharges discordant to the side of MTS. Eight (47%) patients in the MTLE-BHS sub-group had normal medial temporal volume on Scheltens scale. Eight patients among MTLE-BHS underwent surgery (4 following intracranial monitoring that localized to the side of HS) with Engel class I outcome at 1year follow-up in 6 and Engel class II outcome in 2.

CONCLUSION

Attenuation of ipsilateral fast ictal rhythms on scalp EEG as well as neocortical changes are likely to be deterministic factors for MTLE-BHS as opposed to the severity of hippocampal atrophy. Considering good post-operative outcomes, intracranial monitoring for surgical selection is not mandatory in MTLE-BHS despite discordant semiology and ictal onset, in the presence of inter-ictal, functional imaging and neuropsychology data concordant to the side of HS.

Medial temporal lobe epilepsy associated with hippocampal sclerosis is a distinctive syndrome

Epileptic syndromes are distinctive disorders with specific features, which when taken together, permit a specific diagnosis. There is actually a debate on that medial temporal lobe epilepsy with hippocampal sclerosis is an epileptic syndrome. To address this issue, we searched for discriminative semiological features between temporal lobe epilepsy patients with hippocampal sclerosis (TLE-HS patients or group 1), TLE patients with medial structural lesion other than hippocampal sclerosis or in MRI-negative cases with medial onset on further investigations (group 2) and lateral TLE patients (LTLE or group 3). We retrospectively collected data from medical and EEG-video records of 523 TLE patients, referred for surgery to the Pitié-Salpêtrière Epileptology Unit between 1991 and 2014. We identified 389 patients belonging to group 1, 61 patients belonging to group 2, and 73 patients belonging to group 3 and performed a comparative analysis of their clinical data and surgical outcomes. TLE-HS patients (group 1): (1) began epilepsy earlier (11 ± 9 vs. 20 ± 10 vs. 15 ± 9 years); (2) exhibited more frequently early febrile convulsions (FC) (59 vs 7 vs 5%); (3) presented more: ictal gestural automatisms (90 vs 54 vs 67%), dystonic posturing (47 vs 20 vs 23%), and secondary generalized tonic-clonic seizures (GTCS) (70 vs 44% vs 48%) as compared to both groups 2 and 3 patients (all p < 0.001). With respect to auras, abdominal visceral auras were more reported by TLE-HS than by LTLE patients (49 vs 16%). Three cardinal criteria correctly classified 94% of patients into TLE-HS group: history of FC, dystonic posturing, and secondary GTCS. Postoperative outcome was significantly better in TLE-HS group than in the two other groups (p = 0.03 and 0.003). Our study demonstrates that cardinal criteria are reliably helpful to distinguish patients with TLE-HS from those with other TLE and may allow considering TLE-HS as a distinctive syndrome.

Acute and spontaneous seizure onset zones in the intraperitoneal kainic acid model

OBJECTIVE

Hippocampal monitoring is often used in the intraperitoneal kainic acid (KA) seizure model for detection and quantification of early ictal activity. Here, we investigated extra-hippocampal seizure onset zones (SOZs) in this model.

METHODS

Eight male Sprague Dawley rats implanted with depth electrodes were continuously recorded during intraperitoneal KA injections until status epilepticus (SE) was induced. Another group of four rats was monitored chronically up to two weeks after emergence of spontaneous recurrent seizures. All rats had hippocampal electrodes. Other sampled brain regions included, among others, the claustrum, piriform cortex, and orbital cortex. Seizures recorded with video-EEG were visually analyzed.

RESULTS

In the 58 seizures recorded during KA injections, the SOZ was extrahippocampal in 7 (12%), diffuse in 29 (50%), and hippocampal in 22 (38%). Of the 14 spontaneous seizures recorded, none were solely extrahippocampal, 10 (71%) were diffuse, and 4 (29%) were of hippocampal onset. All extra-hippocampal seizures propagated to the hippocampus within 4 to 50s (mean=14, n=7). No distinctive semiological manifestations correlated with the SOZs.

SIGNIFICANCE

We conclude that seizures can have multifocal SOZs in the KA model. This finding is important to consider when using this model, among other purposes, to screen for new therapies, study pharmacoresistance, or investigate comorbidities of epilepsy.

Complex Partial Cluster Seizures in Cats with Orofacial Involvement

Seventeen cats were presented with acute onset of complex partial seizures with orofacial involvement (salivation, facial twitching, lip smacking, chewing, licking or swallowing), motor arrest (motionless starring) and behavioural changes. In 11 cats hippocampal necrosis (HN) was confirmed by histopathology. In a further six cats hippocampal changes were suggested by magnetic resonance imaging. The mean monitoring time of eight cats which were not euthanased in the acute phase of the disease, was 408 days (60–908): four cats are still alive. In all surviving cases, the owners reported a good quality of life. We conclude that an acute cluster of complex partial seizures with orofacial involvement are often associated with HN and that HN is not necessarily a fatal condition. Supportive and antiepileptic therapy can result in remission. The long-term outcome can be good to excellent; therefore, euthanasia should be avoided in the acute phase of the signs.

Dysregulation of PINCH signaling in mesial temporal epilepsy

Mounting evidence suggests that inflammation is important in epileptogenesis. Particularly Interesting New Cysteine Histidine-rich (PINCH) protein is a highly conserved, LIM-domain protein known to interact with hyperphosphorylated Tau. We assessed PINCH expression in resected epileptogenic human hippocampi and further explored the relationships among PINCH, hpTau and associated kinases. Resected hippocampal tissue from 7 patients with mesial temporal lobe epilepsy (MTLE) was assessed by Western analyses to measure levels of PINCH and hyperphosphorylated Tau, as well as changes in phosphorylation levels of associated kinases AKT and GSK3β in comparison to normal control tissue. Immunolabeling was also conducted to evaluate PINCH and hpTau patterns of expression, co-localization and cell-type specific expression. Hippocampal PINCH was increased by 2.6 fold in the epilepsy cases over controls and hpTau was increased 10 fold over control. Decreased phospho-AKT and phospho-GSK3β in epilepsy tissue suggested involvement of this pathway in MTLE. PINCH and hpTau co-localized in some neurons in MTLE tissue. While PINCH was expressed by both neurons and astrocytes in MTLE tissue, hpTau was extracellular or associated with neurons. PINCH was absent from the serum of control subjects but readily detectable from the serum of patients with chronic epilepsy. Our study describes the expression of PINCH and points to AKT/GSK3β signaling dysregulation as a possible pathway in hpTau formation in MTLE. In view of the interactions between hpTau and PINCH, understanding the role of PINCH in MTLE may provide increased understanding of mechanisms leading to inflammation and MTLE epileptogenesis and a potential biomarker for drug-resistant epilepsy.

Altered GABAA receptor density and unaltered blood-brain barrier [11C]flumazenil transport in drug-resistant epilepsy patients with mesial temporal sclerosis

Studies in rodents suggest that flumazenil is a P-glycoprotein substrate at the blood-brain barrier. This study aimed to assess whether [¹¹C]flumazenil is a P-glycoprotein substrate in humans and to what extent increased P-glycoprotein function in epilepsy may confound interpretation of clinical [¹¹C]flumazenil studies used to assess gamma-aminobutyric acid A receptors. Nine drug-resistant patients with epilepsy and mesial temporal sclerosis were scanned twice using [¹¹C]flumazenil before and after partial P-glycoprotein blockade with tariquidar. Volume of distribution, nondisplaceable binding potential, and the ratio of rate constants of [¹¹C]flumazenil transport across the blood-brain barrier (K₁/k₂) were derived for whole brain and several regions. All parameters were compared between pre- and post-tariquidar scans. Regional results were compared between mesial temporal sclerosis and contralateral sides. Tariquidar significantly increased global K₁/k₂ (+23%) and volume of distribution (+10%), but not nondisplaceable binding potential. At the mesial temporal sclerosis side volume of distribution and nondisplaceable binding potential were lower in hippocampus (both ∼-19%) and amygdala (both ∼-16%), but K₁/k₂ did not differ, suggesting that only regional gamma-aminobutyric acid A receptor density is altered in epilepsy. In conclusion, although [¹¹C]flumazenil appears to be a (weak) P-glycoprotein substrate in humans, this does not seem to affect its role as a tracer for assessing gamma-aminobutyric acid A receptor density.

Neuropathology of epilepsy

Epilepsy is one of the most common neurologic disorders, affecting about 50 million people worldwide. The disease is characterized by recurrent seizures, which are due to aberrant neuronal networks resulting in synchronous discharges. The term epilepsy encompasses a large spectrum of syndromes and diseases with different etiopathogenesis. The recent development of imaging and epilepsy surgery techniques is now enabling the identification of structural abnormalities that are part of the epileptic network, and the removal of these lesions may result in control of seizures. Access of this clinically well-characterized neurosurgical material has provided neuropathologists with the opportunity to study a variety of structural brain abnormalities associated with epilepsy, by combining traditional routine histopathologic methods with molecular genetics and functional analysis of the resected tissue. This approach has contributed greatly to a better diagnosis and classification of these structural lesions, and has provided important new insights into their pathogenesis and epileptogenesis. The present chapter provides a detailed description of the large spectrum of histopathologic findings encountered in epilepsy surgery patients, addressing in particular the nonneoplastic pathologies, including hippocampal sclerosis, malformations of cortical development, Sturge-Weber syndrome, and Rasmussen encephalitis, and reviews current knowledge regarding the underlying molecular pathomechanisms and cellular mechanisms mediating hyperexcitability.

Modulation of miR-146a/complement factor H-mediated inflammatory responses in a rat model of temporal lobe epilepsy

Increasing evidence supports the involvement of inflammatory and immune processes in temporal lobe epilepsy (TLE). miRNAs represent small regulatory RNA molecules that have been shown to act as negative regulators of gene expression controlling different biological processes, including immune system homoeostasis and function. We investigated the expression and cellular distribution of miRNA-146a (miR-146a) in a rat model of TLE. Prominent up-regulation of miR-146a activation was evident in 1 week after status epilepticus (SE) and persisted in the chronic phase. The predicted miR-146a's target complement factor H (CFH) mRNA and protein expression was also down-regulated in TLE rat model. Furthermore, transfection of miR-146a mimics in neuronal and glial cells down-regulated CFH mRNA and protein levels respectively. Luciferase reporter assays demonstrated that miR-146a down-regulated CFH mRNA expression via 3'-UTR pairing. Down-regulating miR-146a by intracerebroventricular injection of antagomir-146a enhanced the hippocampal expression of CFH in TLE model and decreased seizure susceptibility. These findings suggest that immunopathological deficits associated with TLE can in part be explained by a generalized miR-146a-mediated down-regulation of CFH that may contribute to epileptogenesis in a rat model of TLE.

Age of onset of mesial temporal lobe epilepsy with hippocampal sclerosis: the effect of apolipoprotein E and febrile seizures

PURPOSE

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is the most frequent pharmaco-resistant epilepsy. It has been associated with febrile seizures (FS) in childhood. Its aetiology remains unclear but genetic factors are involved. Apolipoprotein E (ApoE) is the main lipoprotein secreted in brain. It has a critical immunomodulatory function, influences neurotransmission and it is involved in repairing damaged neurons. ApoE ϵ4 is an isoform of ApoE with altered protein function, previously associated with refractoriness and early onset epilepsy. This study was undertaken to determine if ApoE isoforms are risk factors for MTLE-HS and influence clinical characteristics.

METHODS

A group of 188 MTLE-HS patients (101 F, 87 M, mean age = 44.7 ± 11.6 years, 100 with FS antecedents) was studied and compared with a group of 342 healthy individuals in a case-control genetic association study. Data were analysed with Pearson Chi-squared Test or Student's t test, as appropriated.

RESULTS

No differences in ApoE ϵ4 allelic frequencies between MTLE-HS patients and controls or between MTLE-HS subgroups were observed. Nevertheless, ApoE ϵ4 carriers had an earlier MTLE-HS onset (11.0 ± 7.9 years in ApoE ϵ4 carriers vs. 14.4 ± 11.2 years in ApoE ϵ4 non-carriers p < 0.05). Additionally, we observed that MTLE-HS patients with FS antecedents had a statistically significant early disease onset (11.5 ± 8.7 years in FS⁺ vs. 16.0 ± 12.1 years in FS^-, p < 0.01).

CONCLUSIONS

Our data show that ApoE ϵ4 and FS may not participate directly in etiopathogenic mechanisms of MTLE-HS but could hasten the disease development in predisposed individuals.

Distinctive Structural and Effective Connectivity Changes of Semantic Cognition Network across Left and Right Mesial Temporal Lobe Epilepsy Patients

Occurrence of language impairment in mesial temporal lobe epilepsy (mTLE) patients is common and left mTLE patients always exhibit a primary problem with access to names. To explore different neuropsychological profiles between left and right mTLE patients, the study investigated both structural and effective functional connectivity changes within the semantic cognition network between these two groups and those from normal controls. We found that gray matter atrophy of left mTLE patients was more severe than that of right mTLE patients in the whole brain and especially within the semantic cognition network in their contralateral hemisphere. It suggested that seizure attacks were rather targeted than random for patients with hippocampal sclerosis (HS) in the dominant hemisphere. Functional connectivity analysis during resting state fMRI revealed that subregions of the anterior temporal lobe (ATL) in the left HS patients were no longer effectively connected. Further, we found that, unlike in right HS patients, increased causal linking between ipsilateral regions in the left HS epilepsy patients cannot make up for their decreased contralateral interaction. It suggested that weakened contralateral connection and disrupted effective interaction between subregions of the unitary, transmodal hub of the ATL may be the primary cause of anomia in the left HS patients.

Differential expression of miR-184 in temporal lobe epilepsy patients with and without hippocampal sclerosis - Influence on microglial function

Epilepsy is one of the most common neurological disorders characterized by recurrent seizures due to neuronal hyperexcitability. Here we compared miRNA expression patterns in mesial temporal lobe epilepsy with and without hippocampal sclerosis (mTLE + HS and mTLE −HS) to investigate the regulatory mechanisms differentiating both patient groups. Whole genome miRNA sequencing in surgically resected hippocampi did not reveal obvious differences in expression profiles between the two groups of patients. However, one microRNA (miR-184) was significantly dysregulated, which was confirmed by qPCR. We observed that overexpression of miR-184 inhibited cytokine release after LPS stimulation in primary microglial cells, while it did not affect the viability of murine primary neurons and primary astrocytes. Pathway analysis revealed that miR-184 is potentially involved in the regulation of inflammatory signal transduction and apoptosis. Dysregulation of some the potential miR-184 target genes was confirmed by qPCR and 3′UTR luciferase reporter assay. The reduced expression of miR-184 observed in patients with mTLE + HS together with its anti-inflammatory effects indicate that miR-184 might be involved in the modulation of inflammatory processes associated with hippocampal sclerosis which warrants further studies elucidating the role of miR-184 in the pathophysiology of mTLE.

Quantitative magnetic resonance imaging traits as endophenotypes for genetic mapping in epilepsy

Over the last decade, the field of imaging genomics has combined high-throughput genotype data with quantitative magnetic resonance imaging (QMRI) measures to identify genes associated with brain structure, cognition, and several brain-related disorders. Despite its successful application in different psychiatric and neurological disorders, the field has yet to be advanced in epilepsy. In this article we examine the relevance of imaging genomics for future genetic studies in epilepsy from three perspectives. First, we discuss prior genome-wide genetic mapping efforts in epilepsy, considering the possibility that some studies may have been constrained by inherent theoretical and methodological limitations of the genome-wide association study (GWAS) method. Second, we offer a brief overview of the imaging genomics paradigm, from its original inception, to its role in the discovery of important risk genes in a number of brain-related disorders, and its successful application in large-scale multinational research networks. Third, we provide a comprehensive review of past studies that have explored the eligibility of brain QMRI traits as endophenotypes for epilepsy. While the breadth of studies exploring QMRI-derived endophenotypes in epilepsy remains narrow, robust syndrome-specific neuroanatomical QMRI traits have the potential to serve as accessible and relevant intermediate phenotypes for future genetic mapping efforts in epilepsy.

•

QMRI traits have the potential to serve as robust intermediate phenotypes for brain-related disorders.

•

Hippocampal volume is the most promising neuroimaging endophenotype for MTLE + HS.

•

Imaging genomics holds great promise in advancing epilepsy genetic research.

•

Studies are encouraged to explore the validity of QMRI traits as endophenotypes for epilepsy.

Interictal epileptic discharge correlates with global and frontal cognitive dysfunction in temporal lobe epilepsy

OBJECTIVE

Temporal lobe epilepsy (TLE) with hippocampal sclerosis has widespread effects on structural and functional connectivity and often entails cognitive dysfunction. EEG is mandatory to disentangle interactions in epileptic and physiological networks which underlie these cognitive comorbidities. Here, we examined how interictal epileptic discharges (IEDs) affect cognitive performance.

METHODS

Thirty-four patients (right TLE=17, left TLE=17) were examined with 24-hour video-EEG and a battery of neuropsychological tests to measure intelligence quotient and separate frontal and temporal lobe functions. Hippocampal segmentation of high-resolution T1-weighted imaging was performed with FreeSurfer. Partial correlations were used to compare the number and distribution of clinical interictal spikes and sharp waves with data from imagery and psychological tests.

RESULTS

The number of IEDs was negatively correlated with executive functions, including verbal fluency and intelligence quotient (IQ). Interictal epileptic discharge affected cognitive function in patients with left and right TLE differentially, with verbal fluency strongly related to temporofrontal spiking. In contrast, IEDs had no clear effects on memory functions after corrections with partial correlations for age, age at disease onset, disease duration, and hippocampal volume.

CONCLUSION

In patients with TLE of long duration, IED occurrence was strongly related to cognitive deficits, most pronounced for frontal lobe function. These data suggest that IEDs reflect dysfunctional brain circuitry and may serve as an independent biomarker for cognitive comorbidity.

How do people with drug-resistant mesial temporal lobe epilepsy sleep? A clinical and video-EEG with EOG and submental EMG for sleep staging study

This study aimed to assess subjective and objective sleep parameters in a homogeneous group of drug-resistant mesial temporal lobe epilepsy (MTLE) patients through internationally validated clinical questionnaires, video-electroencephalographic (VEEG) and polysomnographic (PSG) studies. Fifty-six patients with definite diagnosis of MTLE who were candidates for epilepsy surgery underwent a detailed clinical history, the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Stanford Sleepiness Scale (SSS), neurological examination, 1.5 T brain magnetic resonance imaging, VEEG and PSG. Sixteen percent of patients reported significant daytime sleepiness as measured by ESS and 27% reported low levels of sleep quality as measured by PSQI. Patients with medically resistant epilepsy by MTLE showed increased wakefulness after sleep onset (WASO) with mean ± standard deviation of 17.4 ± 15.6, longer non-rapid eye movement (NREM) 1 (7.5 ± 4.6%) and NREM3 sleep (26.6 ± 11.8%), abnormal rapid eye movement (REM) latency in 30/56 patients, shorter REM sleep (16.7 ± 6.6%), and abnormal alpha delta patterns were observed in 41/56 patients. The analysis of interictal epileptic discharges (IEDs) evidenced highest spiking rate during NREM3 sleep and higher concordance with imaging data when IEDs were recorded in sleep, mainly during REM sleep. We concluded that patients with MTLE showed disrupted sleep architecture that may result in daytime dysfunction and sleep complaints. Furthermore, NREM sleep activated focal IEDs and them - when recorded during sleep - had higher localizing value.

Magnetic resonance features of the feline hippocampus in epileptic and non-epileptic cats: a blinded, retrospective, multi-observer study

BACKGROUND

Hippocampal necrosis in cats has been reported to be associated with epileptic seizures. Magnetic resonance imaging (MRI) features of temporal lobe (TL) abnormalities in epileptic cats have been described but MR images from epileptic and non-epileptic individuals have not yet been systematically compared. TL abnormalities are highly variable in shape, size and signal, and therefore may lead to varying evaluations by different specialists. The aim of this study was to investigate whether there were differences in the appearance of the TL between epileptic and non-epileptic cats, and whether there were any relationships between TL abnormalities and seizure semiologies or other clinical findings. We also investigated interobserver agreement among three specialists.

METHODS

The MR images of 46 cats were reviewed independently by three observers, who were blinded to patient data, examination findings and the review of the other observers. Images were evaluated using a multiparametric scoring system developed for this study. Mann-Whitney U-tests and chi-square were used to analyse the differences between observers' evaluations. The kappa coefficient (k) and Fleiss' kappa coefficient were used to quantify interobserver agreement.

RESULTS

The overall interobserver agreement was moderate to good (k =0.405 to 0.615). The MR scores between epileptic and non-epileptic cats did not differ significantly. However, there was a significant difference between the MR scores of epileptic cats with and without orofacial involvement according to all three observers. Likewise, MR scores of cats with cluster seizures were higher than those of cats without clusters.

CONCLUSION

Cats presenting with recurrent epileptic seizures with orofacial involvement are more likely to have hippocampal pathologies, which suggests that TL abnormalities are not merely unspecific epileptic findings, but are associated with a certain type of epilepsy. TL signal alterations are more likely to be detected on FLAIR sequences. In contrast to severe changes in the TL which were described similarly among specialists, mild TL abnormalities may be difficult to interpret, thus leading to different assessments among observers.

Verbal Dominant Memory Impairment and Low Risk for Post-operative Memory Worsening in Both Left and Right Temporal Lobe Epilepsy Associated with Hippocampal Sclerosis

Post-operative memory changes after temporal lobe surgery have been established mainly by group analysis of cognitive outcome. This study investigated individual patient-based memory outcome in surgically-treated patients with mesial temporal lobe epilepsy (TLE). This study included 84 consecutive patients with intractable TLE caused by unilateral hippocampal sclerosis (HS) who underwent epilepsy surgery (47 females, 41 left [Lt] TLE). Memory functions were evaluated with the Wechsler Memory Scale-Revised before and at 1 year after surgery. Pre-operative memory function was classified into three patterns: verbal dominant memory impairment (Verb-D), visual dominant impairment (Vis-D), and no material-specific impairment. Post-operative changes in verbal and visual memory indices were classified into meaningful improvement, worsening, or no significant changes. Pre-operative patterns and post-operative changes in verbal and visual memory function were compared between the Lt and right (Rt) TLE groups. Pre-operatively, Verb-D was the most common type of impairment in both the Lt and Rt TLE groups (65.9 and 48.8%), and verbal memory indices were lower than visual memory indices, especially in the Lt compared with Rt TLE group. Vis-D was observed only in 11.6% of Rt and 7.3% of Lt TLE patients. Post-operatively, meaningful improvement of memory indices was observed in 23.3–36.6% of the patients, and the memory improvement was equivalent between Lt and Rt TLE groups and between verbal and visual materials. In conclusion, Verb-D is most commonly observed in patients with both the Lt and Rt TLE associated with HS. Hippocampectomy can improve memory indices in such patients regardless of the side of surgery and the function impaired.

Involvement of microRNAs in epileptogenesis

Patients who have sustained brain injury or had developmental brain lesions present a non-negligible risk for developing delayed epilepsy. Finding therapeutic strategies to prevent development of epilepsy in at-risk patients represents a crucial medical challenge. Noncoding microRNA molecules (miRNAs) are promising candidates in this area. Indeed, deregulation of diverse brain-specific miRNAs has been observed in animal models of epilepsy as well as in patients with epilepsy, mostly in temporal lobe epilepsy (TLE). Herein we review deregulated miRNAs reported in epilepsy with potential roles in key molecular and cellular processes underlying epileptogenesis, namely neuroinflammation, cell proliferation and differentiation, migration, apoptosis, and synaptic remodeling. We provide an up-to-date listing of miRNAs altered in epileptogenesis and assess recent functional studies that have interrogated their role in epilepsy. Last, we discuss potential applications of these findings for the future development of disease-modifying therapeutic strategies for antiepileptogenesis.