Epidemiology of temporal lobe epilepsy

Theory of mind in epilepsy

Epilepsy is characterized by recurrent, chronic, and unprovoked seizures. Epilepsy has a significant negative impact on a patient's quality of life even if seizures are well controlled. In addition to the distress caused by seizures, patients with epilepsy (PwE) may suffer from cognitive impairment with serious social consequences such as poor interpersonal relationships, loss of employment, and reduced social networks. Pathological changes and functional connectivity abnormalities observed in PwE can disrupt the neural network responsible for the theory of mind. Theory of mind is the ability to attribute mental states to other people (intentions, beliefs, and emotions). It is a complex aspect of social cognition and includes cognitive and affective constructs. In recent years, numerous studies have assessed the relationship between social cognition, including the theory of mind, in PwE, and suggested impairment in this domain. Interventions targeting the theory of mind can be potentially helpful in improving the quality of life of PwE.

Development and validation of a nonverbal consensus-based semantic memory paradigm in patients with epilepsy

OBJECTIVE

Brain areas implicated in semantic memory can be damaged in patients with epilepsy (PWE). However, it is challenging to delineate semantic processing deficits from acoustic, linguistic, and other verbal aspects in current neuropsychological assessments. We developed a new Visual-based Semantic Association Task (ViSAT) to evaluate nonverbal semantic processing in PWE.

METHOD

The ViSAT was adapted from similar predecessors (Pyramids & Palm Trees test, PPT; Camels & Cactus Test, CCT) comprised of 100 unique trials using real-life color pictures that avoid demographic, cultural, and other potential confounds. We obtained performance data from 23 PWE participants and 24 control participants (Control), along with crowdsourced normative data from 54 Amazon Mechanical Turk (Mturk) workers.

RESULTS

ViSAT reached a consensus >90% in 91.3% of trials compared to 83.6% in PPT and 82.9% in CCT. A deep learning model demonstrated that visual features of the stimulus images (color, shape; i.e., non-semantic) did not influence top answer choices (p = 0.577). The PWE group had lower accuracy than the Control group (p = 0.019). PWE had longer response times than the Control group in general and this was augmented for the semantic processing (trial answer) stage (both p < 0.001).

CONCLUSIONS

This study demonstrated performance impairments in PWE that may reflect dysfunction of nonverbal semantic memory circuits, such as seizure onset zones overlapping with key semantic regions (e.g., anterior temporal lobe). The ViSAT paradigm avoids confounds, is repeatable/longitudinal, captures behavioral data, and is open-source, thus we propose it as a strong alternative for clinical and research assessment of nonverbal semantic memory.

Evaluation of the diagnostic utility on 1.5T and 3.0T 1H magnetic resonance spectroscopy for temporal lobe epilepsy

BACKGROUND

1H magnetic resonance spectroscopy (1H-MRS) can be used to study neurological disorders because it can be utilized to examine the concentrations of related metabolites. However, the diagnostic utility of different field strengths for temporal lobe epilepsy (TLE) remains unclear. The purpose of this study is to make quantitative comparisons of metabolites of TLE at 1.5T and 3.0T and evaluate their efficacy.

METHODS

Our retrospective collections included the single-voxel 1H-MRS of 23 TLE patients and 17 healthy control volunteers (HCs) with a 1.5T scanner, as well as 29 TLE patients and 17 HCs with a 3.0T scanner. Particularly, HCs were involved both the scans with 1.5T and 3.0T scanners, respectively. The metabolites, including the N-acetylaspartate (NAA), creatine (Cr), and choline (Cho), were measured in the left or right temporal pole of brain. To analyze the ratio of brain metabolites, including NAA/Cr, NAA/Cho, NAA/(Cho + Cr) and Cho/Cr, four controlled experiments were designed to evaluate the diagnostic utility of TLE on 1.5T and 3.0T MRS, included: (1) 1.5T TLE group vs. 1.5T HCs by the Mann-Whitney U Test, (2) 3.0T TLE group vs. 3.0T HCs by the Mann-Whitney U Test, (3) the power analysis for the 1.5T and 3.0T scanner, and (4) 3.0T HCs vs. 1.5T HCs by Paired T-Test.

RESULTS

Three metabolite ratios (NAA/Cr, NAA/Cho, and NAA/(Cho + Cr) showed the same statistical difference (p < 0.05) in distinguishing the TLE from HCs in the bilateral temporal poles when using 1.5T or 3.0T scanners. Similarly, the power analysis demonstrated that four metabolite ratios (NAA/Cr, NAA/Cho, NAA/(Cho + Cr), Cho/Cr) had similar distinction abilities between 1.5T and 3.0T scanner, denoting both 1.5T and 3.0T scanners were provided with similar sensitivities and reproducibilities for metabolites detection. Moreover, the metabolite ratios of the same healthy volunteers were not statistically different between 1.5T and 3.0T scanners, except for NAA/Cho (p < 0.05).

CONCLUSIONS

1.5T and 3.0T scanners may have comparable diagnostic potential when 1H-MRS was used to diagnose patients with TLE.

The effects of Src tyrosine kinase inhibitor, saracatinib, on the markers of epileptogenesis in a mixed-sex cohort of adult rats in the kainic acid model of epilepsy

Neurodegeneration and neuroinflammation are key processes of epileptogenesis in temporal lobe epilepsy (TLE). A considerable number (∼30%) of patients with epilepsy are resistant to currently available antiseizure drugs and thus there is a need to develop adjunct therapies to modify disease progression. A vast majority of interventional strategies to treat TLE have utilized males which limits the translational nature of the studies. In this study, we investigated the effects of repeated low-dose kainic acid (KA) injection on the initial status epilepticus (SE) and the effects of Src kinase inhibitor, saracatinib (SAR/AZD0530; 20 mg/kg, oral, daily for 7 days), in a mixed-sex cohort of adult Sprague Dawley rats during early epileptogenesis. There were no sex differences in response to KA-induced SE, and neither did the stage of estrus influence SE severity. KA-induced SE caused significant astrogliosis and microgliosis across the hippocampus, piriform cortex, and amygdala. SAR treatment resulted in a significant reduction of microgliosis across brain regions. Microglial morphometrics such as branch length and the endpoints strongly correlated with CD68 expression in the vehicle-treated group but not in the SAR-treated group, indicating mitigation by SAR. KA-induced SE caused significant neuronal loss, including parvalbumin-positive inhibitory neurons, in both vehicle (VEH) and SAR-treated groups. SAR treatment significantly mitigated FJB-positive neuronal counts as compared to the VEH group. There was an increase in C3-positive reactive astrocytes in the VEH-treated group, and SAR treatment significantly reduced the increase in the piriform cortex. C3-positive astrogliosis significantly correlated with CD68 expression in the amygdala (AMY) of VEH-treated rats, and SAR treatment mitigated this relationship. There was a significant increase of pSrc(Y419)-positive microglia in both KA-treated groups with a statistically insignificant reduction by SAR. KA-induced SE caused the development of classical glial scars in the piriform cortex (PIR) in both KA-treated groups, while SAR treatment led to a 42.17% reduction in the size of glial scars. We did not observe sex differences in any of the parameters in this study. SAR, at the dose tested in the rat kainate model for a week in this study mitigated some of the markers of epileptogenesis in both sexes.

Dopamine and Glutamate Crosstalk Worsen the Seizure Outcome in TLE-HS Patients

Temporal lobe epilepsy (TLE), accompanied by hippocampal sclerosis (HS), is the most common form of drug-resistant epilepsy (DRE). Nearly 20% of the patients showed seizure recurrence even after surgery, and the reasons are yet to be understood. Dysregulation of neurotransmitters is evident during seizures, which can induce excitotoxicity. The present study focused on understanding the molecular changes associated with Dopamine (DA) and glutamate signaling and their possible impact on the persistence of excitotoxicity and seizure recurrence in patients with drug-resistant TLE-HS who underwent surgery. According to the International League against Epilepsy (ILAE) suggested classification for seizure outcomes, the patients (n = 26) were classified as class 1 (no seizures) and class 2 (persistent seizures) using the latest post-surgery follow-up data to understand the prevalent molecular changes in seizure-free and seizure-recurrence patient groups. Our study uses thioflavin T assay, western blot analysis, immunofluorescence assays, and fluorescence resonance energy transfer (FRET) assays. We have observed a substantial increase in the DA and glutamate receptors that promote excitotoxicity. Patients who had seizure recurrence showed a significant increase in (pNR2B, p < 0.009; and pGluR1, p < 0.01), protein phosphatase1γ (PP1γ; p < 0.009), protein kinase A (PKAc; p < 0.001) and dopamine-cAMP regulated phospho protein32 (pDARPP32T34; p < 0.009) which are critical for long-term potentiation (LTP), excitotoxicity compared to seizure-free patients and controls. A significant increase in D1R downstream kinases like PKA (p < 0.001), pCAMKII (p < 0.009), and Fyn (p < 0.001) was observed in patient samples compared to controls. Anti-epileptic DA receptor D2R was found to be decreased in ILAE class 2 (p < 0.02) compared to class 1. Since upregulation of DA and glutamate signaling supports LTP and excitotoxicity, we believe it could impact seizure recurrence. Further studies about the impact of DA and glutamate signaling on the distribution of PP1γ at postsynaptic density and synaptic strength could help us understand the seizure microenvironment in patients. Dopamine, Glutamate signal crosstalk. Diagram representing the PP1γ regulation by NMDAR negative feedback inhibition signaling (green circle-left) and D1R signal (red circle-middle) domination over PP1γ though increased PKA, pDARPP32T34, and supports pGluR1, pNR2B in seizure recurrent patients. D1R-D2R hetero dimer activation (red circle-right) increases cellular Ca2+ and pCAMKIIα activation. All these events lead to calcium overload in HS patients and excitotoxicity, particularly in patients experiencing recurrent seizures.

Heart rate variability modifications in adult patients with early versus late-onset temporal lobe epilepsy: A comparative observational study

OBJECTIVES

Temporal lobe epilepsy (TLE) is the most frequent form of focal epilepsy. TLE is associated with cardio-autonomic dysfunction and increased cardiovascular (CV) risk in patients over the fifth decade of age. In these subjects, TLE can be classified as early-onset (EOTLE; i.e., patients who had developed epilepsy in their youth) and late-onset (LOTLE; i.e., patients who developed epilepsy in adulthood). Heart rate variability (HRV) analysis is useful for assessing cardio-autonomic function and identifying patients with increased CV risk. This study compared changes in HRV occurring in patients over the age of 50, with EOTLE or LOTLE.

METHODS

We enrolled twenty-seven adults with LOTLE and 23 with EOTLE. Each patient underwent a EEG and EKG recording during 20-minutes of resting state and a 5-minutes hyperventilation (HV). Short-term HRV analysis was performed both in time and frequency domains. Linear Mixed Models (LMM) were used to analyze HRV parameters according to the condition (baseline and HV) and group (LOTLE and EOTLE groups).

RESULTS

Compared to the LOTLE group, the EOTLE group showed significantly decreased LnRMSSD (natural logarithm of the root mean square of the difference between contiguous RR intervals) (p-value=0.05), LnHF ms² (natural logarithm of high frequency absolute power) (p-value=0.05), HF n.u. (high frequency power expressed in normalized units) (p-value=0.008) and HF% (high frequency power expressed in percentage) (p-value=0.01). In addition, EOTLE patients exhibited increased LF n.u. (low frequency power expressed in normalized units) (p-value=0.008) and LF/HF (low frequency/high frequency) ratio (p-value=0.007). During HV, the LOTLE group exhibited a multiplicative effect for the interaction between group and condition with increased LF n.u. (p = 0.003) and LF% (low frequency expressed in percentage) (p = 0.05) values.

CONCLUSIONS

EOTLE is associated with reduced vagal tone compared to LOTLE. Patients with EOTLE may have a higher risk of developing cardiac dysfunction or cardiac arrhythmia than LOTLE patients.

Human cortical interneurons optimized for grafting specifically integrate, abort seizures, and display prolonged efficacy without over-inhibition

Previously, we demonstrated the efficacy of human pluripotent stem cell (hPSC)-derived GABAergic cortical interneuron (cIN) grafts in ameliorating seizures. However, a safe and reliable clinical translation requires a mechanistic understanding of graft function, as well as the assurance of long-term efficacy and safety. By employing hPSC-derived chemically matured migratory cINs in two models of epilepsy, we demonstrate lasting efficacy in treating seizures and comorbid deficits, as well as safety without uncontrolled growth. Host inhibition does not increase with increasing grafted cIN densities, assuring their safety without the risk of over-inhibition. Furthermore, their closed-loop optogenetic activation aborted seizure activity, revealing mechanisms of graft-mediated seizure control and allowing graft modulation for optimal translation. Monosynaptic tracing shows their extensive and specific synaptic connections with host neurons, resembling developmental connection specificity. These results offer confidence in stem cell-based therapy for epilepsy as a safe and reliable treatment for patients suffering from intractable epilepsy.

Neuropsychological Phenotypes in Pediatric Temporal Lobe Epilepsy

OBJECTIVE

Adults with temporal lobe epilepsy (TLE) have been found to have a fairly characteristic pattern of neuropsychological performance, but there is considerably less research and more variability in findings with children. Because the cognitive domains included in most studies with children have been limited, the current study attempted to better characterize the cognitive phenotype of children with TLE using a broader neuropsychological battery.

METHODS

The study included 59 children with TLE (59% male) age 7 to 16 (M = 12.67; SD = 3.12) who underwent comprehensive neuropsychological evaluation. Patient results were grouped into cognitive domains (reasoning, language, visuoperceptual, verbal memory, executive function, and motor function) based upon their test performance. These factor scores were subjected to Ward's hierarchical clustering method with squared Euclidean distance.

RESULTS

Cluster analysis revealed three distinct cognitive profiles: (1) normal functioning (20% of sample); (2) delayed verbal memory and motor weaknesses (61% of the sample); and (3) global impairment (19% of the sample). Cluster 3 had longer epilepsy duration and a higher incidence of hippocampal sclerosis (HS) compared to Cluster 1 (p < .05). There were no significant differences among the three cluster groups on demographic characteristics or remaining clinical characteristics.

CONCLUSIONS

Children with TLE present with distinct cognitive phenotypes ranging from average performance to global impairment. Results partially support previous hypotheses highlighting the cumulative neurobiological burden on the developing brain in the context of chronic epilepsy and provide a preliminary framework for the cognitive domains most vulnerable to the TLE disease process.

Global network alterations of the cognitive phenotypes in pediatric temporal lobe epilepsy

OBJECTIVE

An emerging literature suggests that the neuropsychological sequelae of pediatric temporal lobe epilepsy (TLE) are characterized by a continuum of cognitive phenotypes that range in type and severity. The goal of the present investigation was to better characterize the neuropsychological networks that underlie these phenotypes.

METHODS

The study included 59 patients with TLE who were empirically categorized into three cognitive phenotypes (normal, focal, and generalized impairment). Nine neuropsychological measures representing multiple cognitive domains (i.e., reasoning, language, visouperception, memory, and executive function) were examined by graph theory to characterize the global network properties of the cognitive phenotypes.

RESULTS

Across the cognitive phenotype groups (i.e., normal, focal, generalized impaired) the following findings emerged: (1) the adjacency matrices demonstrated different patterns of association between cognitive measures within the neuropsychological network; (2) global measures including global efficiency (GE) and average clustering coefficient (aCC) showed a stepwise increase across the range of impaired pediatric TLE phenotypes; however, modularity (M) demonstrated the opposite pattern.

IMPRESSIONS

Cognitive networks in pediatric TLE demonstrate stepwise perturbation in underlying neuropsychological networks. Graph theory offers a novel approach to examine cognitive abnormalities in pediatric TLE that may be applied to other pediatric epilepsies.

Magnetoencephalography Imaging Reveals Abnormal Information Flow in Temporal Lobe Epilepsy

Background/Introduction: Widespread network disruption has been hypothesized to be an important predictor of outcomes in patients with refractory temporal lobe epilepsy (TLE). Most studies examining functional network disruption in epilepsy have largely focused on the symmetric bidirectional metrics of the strength of network connections. However, a more complete description of network dysfunction impacts in epilepsy requires an investigation of the potentially more sensitive directional metrics of information flow. Methods: This study describes a whole-brain magnetoencephalography-imaging approach to examine resting-state directional information flow networks, quantified by phase-transfer entropy (PTE), in patients with TLE compared with healthy controls (HCs). Associations between PTE and clinical characteristics of epilepsy syndrome are also investigated. Results: Deficits of information flow were specific to alpha-band frequencies. In alpha band, while HCs exhibit a clear posterior-to-anterior directionality of information flow, in patients with TLE, this pattern of regional information outflow and inflow was significantly altered in the frontal and occipital regions. The changes in information flow within the alpha band in selected brain regions were correlated with interictal spike frequency and duration of epilepsy. Conclusions: Impaired information flow is an important dimension of network dysfunction associated with the pathophysiological mechanisms of TLE.

Impaired Emotion Processing and Panic Disorder After Left Anterior Temporal Lobectomy: A Case Report of Successful Psychotherapeutic Intervention

Background

Over the last decades, brain surgery became a more frequently applied treatment for temporal lobe epilepsy (TLE). Despite its success, several studies found de-novo post-operative psychiatric symptoms in TLE surgery patients. Cognitive behavioural therapy is effective to treat brain healthy psychiatric patients but might not be translatable to patients with resections in emotion regulating networks as these areas seem to be essentially involved in successful psychotherapeutic treatment.

Methods

Here we report the case of a female patient with medically refractory medial temporal lobe epilepsy resulting in left anterior temporal lobectomy at age 35. Post operation she did not show adequate fearful response but at the same time manifested symptoms of a severe panic disorder. We investigated if this patient, despite lesions in emotion-behaviour brain circuits, can benefit from cognitive behavioural therapy.

Results

The intervention, customized to the specific resources and difficulties of the patient, was effective in stopping panic attacks and improving social functioning.

Conclusions

This case shows that MTL brain surgery patients may benefit from CBT and demonstrates the important and if yet still somewhat mysterious role of the amygdala in emotion regulation processes.

Behavioral phenotypes of pediatric temporal lobe epilepsy

OBJECTIVE

A broad spectrum of emotional-behavioral problems have been reported in pediatric temporal lobe epilepsy (TLE), but with considerable variability in their presence and nature of expression, which hampers precise identification and treatment. The present study aimed to empirically identify latent patterns or behavioral phenotypes and their correlates.

METHODS

Data included parental ratings of emotional-behavioral status on the Behavior Assessment System for Children, 2nd Edition (BASC-2) of 81 children (mean age = 11.79, standard deviation [SD] = 3.93) with TLE. The nine clinical subscales were subjected to unsupervised machine learning to identify behavioral subgroups. To explore concurrent validity and the underlying composition of the identified clusters, we examined demographic factors, seizure characteristics, psychosocial factors, neuropsychological performance, psychiatric status, and health-related quality of life (HRQoL).

RESULTS

Three behavioral phenotypes were identified, which included no behavioral concerns (Cluster 1, 43% of sample), externalizing problems (Cluster 2, 41% of sample), and internalizing problems (Cluster 3, 16% of sample). Behavioral phenotypes were characterized by important differences across clinical seizure variables, psychosocial/familial factors, everyday executive functioning, and HRQoL. Cluster 2 was associated with younger child age, lower maternal education, and higher rate of single-parent households. Cluster 3 was associated with older age at epilepsy onset and higher rates of hippocampal sclerosis and parental psychiatric history. Both Cluster 2 and 3 demonstrated elevated family stress. Concurrent validity was demonstrated through the association of psychiatric (i.e., rate of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) disorders and psychotropic medication) and parent-rated HRQoL variables.

SIGNIFICANCE

Youth with TLE present with three distinct behavioral phenotypes that correspond with important clinical and sociodemographic markers. The current findings demonstrate the variability of behavioral presentations in youth with TLE and provide a preliminary framework for screening and targeting intervention to enhance support for youth with TLE and their families.

Cluster analysis: Predicting the seizure outcome in temporal lobe epilepsy

OBJECTIVES

We applied the Two-Step cluster analysis on a large cohort of patients with temporal lobe epilepsy (TLE). We hypothesized that there are distinct clusters of patients with TLE based on their clinical characteristics and these clusters may predict their seizure outcome.

METHODS

This was a longitudinal study of a prospectively developed database. All patients with a diagnosis of TLE were studied at the outpatient epilepsy clinic, Shiraz, Iran, from 2008 until 2021. The Two-Step cluster analysis (Schwarz's Bayesian Criterion: BIC) was applied to the whole dataset considering the demographic data, clinical characteristics, imaging, and electroencephalography data. The seizure outcome was compared between the clusters of patients.

RESULTS

Three hundred and seventy-four patients had the inclusion criteria and were studied. The Two-Step cluster analysis showed that there were two distinct clusters of patients with TLE. The most important clinical predictors were the presence (or absence) of focal impaired awareness seizures or focal to bilateral tonic-clonic seizures, aura with seizures, and the brain imaging findings. The seizure outcomes were significantly different between these two clusters (p = 0.008).

CONCLUSION

The Two-Step cluster analysis could identify two distinct clusters of patients with TLE; these data are helpful in providing prognosis and counseling for patients and their care-givers. These data may also be used to develop a practical outcome prediction tool for patients with TLE.

Comparison of T2 relaxometry and PET CT in the evaluation of patients with mesial temporal lobe epilepsy using video EEG as the reference standard

PURPOSE

Our study aimed to compare the sensitivity of T2 relaxometry and positron emission tomography - computed tomography (PET/CT) in patients with a history suggestive of mesial temporal lobe epilepsy using video electroencephalography (EEG) as the reference standard.

MATERIAL AND METHODS

In our study, 35 patients with a history suggestive of mesial temporal lobe epilepsy were subjected to conventional magnetic resonance imaging (MRI), T2 relaxometry, and PET/CT. The results of each of the studies were compared with video EEG findings. Analyses were performed by using statistical software (SPSS version 20.0 for windows), and the sensitivity of conventional MRI, T2 relaxometry, and PET/CT were calculated.

RESULTS

The sensitivity of qualitative MRI (atrophy and T2 hyperintensity), quantitative MRI (T2 relaxometry), and PET/CT in lateralizing the seizure focus were 68.6% (n = 24), 85.7% (n = 30), and 88.6% (n = 31), respectively.

CONCLUSIONS

The sensitivity of MRI in lateralization and localization of seizure focus in temporal lobe epilepsy can be increased by adding the quantitative parameter (T2 relaxometry) with the conventional sequences. T2 Relaxometry is comparable to PET/CT for localization and lateralization of seizure focus and is a useful tool in the workup of TLE patients.

Role of glutamate excitotoxicity and glutamate transporter EAAT2 in epilepsy: Opportunities for novel therapeutics development

Epilepsy is a complex neurological syndrome characterized by seizures resulting from neuronal hyperexcitability and sudden and synchronized bursts of electrical discharges. Impaired astrocyte function that results in glutamate excitotoxicity has been recognized to play a key role in the pathogenesis of epilepsy. While there are 26 drugs marketed as anti-epileptic drugs no current treatments are disease modifying as they only suppress seizures rather than the development and progression of epilepsy. Excitatory amino acid transporters (EAATs) are critical for maintaining low extracellular glutamate concentrations and preventing excitotoxicity. When extracellular glutamate concentrations rise to abnormal levels, glutamate receptor overactivation and the subsequent excessive influx of calcium into the post-synaptic neuron can trigger cell death pathways. In this review we discuss targeting EAAT2, the predominant glutamate transporter in the CNS, as a promising approach for developing therapies for epilepsy. EAAT2 upregulation via transcriptional and translational regulation has proven successful in vivo in reducing spontaneous recurrent seizures and offering neuroprotective effects. Another approach to regulate EAAT2 activity is through positive allosteric modulation (PAM). Novel PAMs of EAAT2 have recently been identified and are under development, representing a promising approach for the advance of novel therapeutics for epilepsy.

Cognitive Impairment and Mossy Fiber Sprouting in a Rat Model of Drug-Resistant Epilepsy Induced by Lithium-Pilocarpine

BACKGROUND

The mossy fiber sprouting (MFS) in the dentate gyrus is a common pathological change of epilepsy. Previous studies suggested that it is associated with drug-resistant epilepsy, and mossy cells control spontaneous seizures and spatial memory.

METHODS

We investigated the correlations among cognitive impairment, MFS, seizure frequency and drug resistance in a rat model of epilepsy induced by lithium-pilocarpine. Phenytoin and phenobarbital were used to screen drug resistance. Cognitive function and MFS were detected through the novel object recognition (NOR) test, Morris water maze (MWM) test and Timm staining.

RESULTS

The results showed that object memory and spatial memory functions were both significantly impaired in rats with epilepsy, and only spatial memory impairment was more severe in rats with drug-resistant epilepsy. More frequent spontaneous seizures and more obvious MFS were observed in the drug-resistant rats. The seizure frequency was significantly associated with the MWM performance but not with the NOR performance in rats with epilepsy. The degree of MFS was significantly associated with seizure frequency and spatial memory function.

CONCLUSION

Taken together, these correlations among drug resistance, seizure frequency, spatial memory impairment and MFS suggested the possibility of a common pathological mechanism. More studies are needed to clarify the underlying mechanism behind these correlations and the detailed role of MFS in epilepsy. The mechanism of mossy cell change may be an important target for the treatment of seizures, drug resistance and cognitive dysfunction in patients with epilepsy.

Seizure and social outcomes in patients with non-surgically treated temporal lobe epilepsy

OBJECTIVES

To investigate the seizure outcome with medical treatment in patients with temporal lobe epilepsy (TLE) and its associated factors. We also investigated the social outcome of the patients.

METHODS

This was a retrospective study of a prospectively built electronic database of patients with epilepsy. All patients with a diagnosis of TLE were studied at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran, from 2008 until 2019. In a phone call to the patients, at least 24 months after their diagnosis at our center, we investigated their current seizure control and social status.

RESULTS

Two hundred and twenty-two patients were studied; 101 patients (45.5%) were seizure free. A lower number of the prescribed drugs was the only factor with a significant association with the seizure-free outcome (Odds Ratio: 1.460; p = 0.001). At the time of the phone call, 76 patients (37.6%) reported having a college education, 103 patients (51%) were employed, 146 patients (72.3%) were married, and 81 patients (40%) reported driving a motor vehicle. The employment status, college education, and driving a motor vehicle were significantly associated with a seizure-free outcome status. The social achievements of the patients, who were partially responsive to medical therapy, were significantly worse than those who were seizure free.

CONCLUSION

Many patients with TLE may suffer from drug-resistant seizures. Ongoing seizures in these patients may affect their social lives substantially. Seizure reduction (not freedom) is not good enough to help the patients with TLE enjoy a healthy life with satisfactory social achievements.

The interplay of seizures-induced axonal sprouting and transcription-dependent Bdnf repositioning in the model of temporal lobe epilepsy

The Brain-Derived Neurotrophic Factor is one of the most important trophic proteins in the brain. The role of this growth factor in neuronal plasticity, in health and disease, has been extensively studied. However, mechanisms of epigenetic regulation of Bdnf gene expression in epilepsy are still elusive. In our previous work, using a rat model of neuronal activation upon kainate-induced seizures, we observed a repositioning of Bdnf alleles from the nuclear periphery towards the nuclear center. This change of Bdnf intranuclear position was associated with transcriptional gene activity. In the present study, using the same neuronal activation model, we analyzed the relation between the percentage of the Bdnf allele at the nuclear periphery and clinical and morphological traits of epilepsy. We observed that the decrease of the percentage of the Bdnf allele at the nuclear periphery correlates with stronger mossy fiber sprouting-an aberrant form of excitatory circuits formation. Moreover, using in vitro hippocampal cultures we showed that Bdnf repositioning is a consequence of transcriptional activity. Inhibition of RNA polymerase II activity in primary cultured neurons with Actinomycin D completely blocked Bdnf gene transcription and repositioning occurring after neuronal excitation. Interestingly, we observed that histone deacetylases inhibition with Trichostatin A induced a slight increase of Bdnf gene transcription and its repositioning even in the absence of neuronal excitation. Presented results provide novel insight into the role of BDNF in epileptogenesis. Moreover, they strengthen the statement that this particular gene is a good candidate to search for a new generation of antiepileptic therapies.

Causal relationship of CA3 back-projection to the dentate gyrus and its role in CA1 fast ripple generation

BACKGROUND

Pathophysiological evidence from temporal lobe epilepsy models highlights the hippocampus as the most affected structure due to its high degree of neuroplasticity and control of the dynamics of limbic structures, which are necessary to encode information, conferring to it an intrinsic epileptogenicity. A loss in this control results in observable oscillatory perturbations called fast ripples, in epileptic rats those events are found in CA1, CA3, and the dentate gyrus (DG), which are the principal regions of the trisynaptic circuit of the hippocampus. The present work used Granger causality to address which relationships among these three regions of the trisynaptic circuit are needed to cause fast ripples in CA1 in an in vivo model. For these purposes, male Wistar rats (210-300 g) were injected with a single dose of pilocarpine hydrochloride (2.4 mg/2 µl) into the right lateral ventricle and video-monitored 24 h/day to detect spontaneous and recurrent seizures. Once detected, rats were implanted with microelectrodes in these regions (fixed-recording tungsten wire electrodes, 60-μm outer diameter) ipsilateral to the pilocarpine injection. A total of 336 fast ripples were recorded and probabilistically characterized, from those fast ripples we made a subset of all the fast ripple events associated with sharp-waves in CA1 region (n = 40) to analyze them with Granger Causality.

RESULTS

Our results support existing evidence in vitro in which fast ripple events in CA1 are initiated by CA3 multiunit activity and describe a general synchronization in the theta band across the three regions analyzed DG, CA3, and CA1, just before the fast ripple event in CA1 have begun.

CONCLUSION

This in vivo study highlights the causal participation of the CA3 back-projection to the DG, a connection commonly overlooked in the trisynaptic circuit, as a facilitator of a closed-loop among these regions that prolongs the excitatory activity of CA3. We speculate that the loss of inhibitory drive of DG and the mechanisms of ripple-related memory consolidation in which also the CA3 back-projection to DG has a fundamental role might be underlying processes of the fast ripples generation in CA1.

The Subcortical-Allocortical- Neocortical continuum for the Emergence and Morphological Heterogeneity of Pyramidal Neurons in the Human Brain

Human cortical and subcortical areas integrate emotion, memory, and cognition when interpreting various environmental stimuli for the elaboration of complex, evolved social behaviors. Pyramidal neurons occur in developed phylogenetic areas advancing along with the allocortex to represent 70-85% of the neocortical gray matter. Here, we illustrate and discuss morphological features of heterogeneous spiny pyramidal neurons emerging from specific amygdaloid nuclei, in CA3 and CA1 hippocampal regions, and in neocortical layers II/III and V of the anterolateral temporal lobe in humans. Three-dimensional images of Golgi-impregnated neurons were obtained using an algorithm for the visualization of the cell body, dendritic length, branching pattern, and pleomorphic dendritic spines, which are specialized plastic postsynaptic units for most excitatory inputs. We demonstrate the emergence and development of human pyramidal neurons in the cortical and basomedial (but not the medial, MeA) nuclei of the amygdala with cells showing a triangular cell body shape, basal branched dendrites, and a short apical shaft with proximal ramifications as "pyramidal-like" neurons. Basomedial neurons also have a long and distally ramified apical dendrite not oriented to the pial surface. These neurons are at the beginning of the allocortex and the limbic lobe. "Pyramidal-like" to "classic" pyramidal neurons with laminar organization advance from the CA3 to the CA1 hippocampal regions. These cells have basal and apical dendrites with specific receptive synaptic domains and several spines. Neocortical pyramidal neurons in layers II/III and V display heterogeneous dendritic branching patterns adapted to the space available and the afferent inputs of each brain area. Dendritic spines vary in their distribution, density, shapes, and sizes (classified as stubby/wide, thin, mushroom-like, ramified, transitional forms, "atypical" or complex forms, such as thorny excrescences in the MeA and CA3 hippocampal region). Spines were found isolated or intermingled, with evident particularities (e.g., an extraordinary density in long, deep CA1 pyramidal neurons), and some showing a spinule. We describe spiny pyramidal neurons considerably improving the connectional and processing complexity of the brain circuits. On the other hand, these cells have some vulnerabilities, as found in neurodegenerative Alzheimer's disease and in temporal lobe epilepsy.

Short-Term Amygdala Low-Frequency Stimulation Does not Influence Hippocampal Interneuron Changes Observed in the Pilocarpine Model of Epilepsy

Temporal lobe epilepsy (TLE) is characterized by changes in interneuron numbers in the hippocampus. Deep brain stimulation (DBS) is an emerging tool to treat TLE seizures, although its mechanisms are not fully deciphered. We aimed to depict the effect of amygdala DBS on the density of the most common interneuron types in the CA1 hippocampal subfield in the lithium-pilocarpine model of epilepsy. Status epilepticus was induced in male Wistar rats. Eight weeks later, a stimulation electrode was implanted to the left basolateral amygdala of both pilocarpine-treated (Pilo, n = 14) and age-matched control rats (n = 12). Ten Pilo and 4 control animals received for 10 days 4 daily packages of 50 s 4 Hz regular stimulation trains. At the end of the stimulation period, interneurons were identified by immunolabeling for parvalbumin (PV), neuropeptide Y (NPY), and neuronal nitric oxide synthase (nNOS). Cell density was determined in the CA1 subfield of the hippocampus using confocal microscopy. We found that PV+ cell density was preserved in pilocarpine-treated rats, while the NPY+/nNOS+ cell density decreased significantly. The amygdala DBS did not significantly change the cell density in healthy or in epileptic animals. We conclude that DBS with low frequency applied for 10 days does not influence interneuron cell density changes in the hippocampus of epileptic rats.

Presurgical Language Mapping in Patients With Intractable Epilepsy: A Review Study

INTRODUCTION

about 20% to 30% of patients with epilepsy are diagnosed with drug-resistant epilepsy and one third of these are candidates for epilepsy surgery. Surgical resection of the epileptogenic tissue is a well-established method for treating patients with intractable focal epilepsy. Determining language laterality and locality is an important part of a comprehensive epilepsy program before surgery. Functional Magnetic Resonance Imaging (fMRI) has been increasingly employed as a non-invasive alternative method for the Wada test and cortical stimulation. Sensitive and accurate language tasks are essential for any reliable fMRI mapping.

METHODS

The present study reviews the methods of presurgical fMRI language mapping and their dedicated fMRI tasks, specifically for patients with epilepsy.

RESULTS

Different language tasks including verbal fluency are used in fMRI to determine language laterality and locality in different languages such as Persian. there are some considerations including the language materials and technical protocols for task design that all presurgical teams should take into consideration.

CONCLUSION

Accurate presurgical language mapping is very important to preserve patients language after surgery. This review was the first part of a project for designing standard tasks in Persian to help precise presurgical evaluation and in Iranian PWFIE.

Behavioral and EEGraphic Characterization of the Anticonvulsant Effects of the Predator Odor (TMT) in the Amygdala Rapid Kindling, a Model of Temporal Lobe Epilepsy

Background: Clinical and experimental evidence indicates that olfactory stimulation modulates limbic seizures, either blocking or inducing ictal activity.

Objective: We aim to evaluate the behavioral and electroencephalographic (EEGraphic) effects of dihydro-2,4,5-trimethylthiazoline (TMT) olfactory exposure on limbic seizures induced by amygdala rapid kindling (ARK).

Materials and Methods: Wistar male rats (280–300 g) underwent stereotaxic surgery for electrode implantation in piriform cortex (PC), hippocampal formation (HIP), and amygdaloid complex (AMYG). Part of the animals was exposed to a saturated chamber with water or TMT, while others had ARK and olfactory exposure prior to the 21st stimulus. Behavioral responses were measured by traditional seizure severity scales (Racine and Pinel and Rovner) and/or by sequential analysis/neuroethology. The electrographic activity of epileptogenic limbic networks was quantified by the occurrence of the first and second EEG afterdischarges, comparing the 1st and 21st stimulus. The spectral analysis [Fast Fourier Transform (FFT)] of the first afterdischarge was performed at the 21st stimulus.

Results: TMT olfactory exposure reduced the seizure severity in kindled rats, altering the displayed behavioral sequence. Moreover, TMT decreased the occurrence of first and second afterdischarges, at the 21st stimulus, and altered the spectral features.

Conclusions: Both behavioral and EEGraphic evaluations indicated that TMT, a potent molecule with strong biological relevance, in fact, “predator odor,” suppressed the epileptiform activity in limbic networks.

Evaluation of patients with late-onset and medically refractory temporal lobe epilepsy with mesial temporal sclerosis

OBJECTIVES

Our study aims to compare demographics, clinical features and postsurgical outcomes between early and late-onset patients with medically refractory temporal lobe epilepsy (TLE) related to mesial temporal sclerosis (MTS).

PATIENTS AND METHODS

Seventy-one patients admitting to the Epilepsy Clinic of Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine between 1995-2015, who were diagnosed with refractory TLE related to MTS, were included in our study. All of these patients were resistant to medical treatment, and thus candidates for, or underwent surgery, and had no pathology other than MTS in their cranial magnetic resonance imaging (MRI). Based on previous studies, those patients were divided into two categories as "early-onset" and "late-onset", according to the age-onset of afebrile recurrent seizures, where the cutoff was determined as 20 years. Demographics, clinical features, and postsurgical outcomes were compared between both groups.

RESULTS

Fifty-three patients included in our study had early-onset MTS-TLE, and 18 patients had late-onset MTS-TLE. Demographics, clinical features, characteristics of electroencephalography (EEG), MRI, PET MRI/CT, neuropsychometric test (NPT) and postsurgical outcomes were similar in both groups.

CONCLUSION

In both the early-onset and late-onset groups, the presence of similar demographics, clinical features, and postoperative outcomes have suggested that the course of the disease and the success of surgical treatment were not associated with the age-onset of seizures in TLE related to MTS.

Interictal Heart Rate Variability Analysis Reveals Lateralization of Cardiac Autonomic Control in Temporal Lobe Epilepsy

Purpose: The temporal lobe, a critical hub for cognition, also plays a central role in the regulation of autonomic cardiovascular functions. Lesions in this area are usually associated with abnormalities in the regulation of heart rate (HR) and blood pressure (BP). The analysis of the heart rate variability (HRV) is useful to evaluate the cardiac parasympathetic nervous system activity. This study aims at comparing HRV changes occurring in two groups of patients suffering from Temporal Lobe Epilepsy (TLE). To that aim, we evaluated patients differentiated by the right or left location of the epileptic foci.

Materials and Methods: Fifty-two adult patients with a diagnosis of TLE were enrolled. Each patient underwent a 20-min EEG + EKG recording in resting state. According to the localization of epileptic focus, patients were divided into two subgroups: right TLE (R-TLE) and left TLE (L-TLE). HRV parameters were calculated with a short-lasting analysis of EKG recordings. Time-domain and frequency domain-related, as well as non-linear analysis, parameters, were compared between the two groups.

Results: Compared to the R-TLE group, L-TLE subjects showed a significant decrease in low frequency (LF) (p < 0.01) and low frequency/high-frequency ratio (LF/HF) (p < 0.001) as well as increased HF values (p < 0.01), a parameter indicative of the presence of an increased cardiac vagal tone. These results were also confirmed in the subgroup analysis that took into account the seizure types, responses to antiepileptic drugs, seizure frequencies, and etiology.

Conclusions: The main finding of the study is that, compared to R-TLE, L-TLE is associated with increased cardiac vagal tone. These results indicate that patients with TLE exhibit a lateralized cardiac autonomic control. L-TLE patients may have a lower risk of developing cardiac dysfunctions and less susceptible to develop Sudden Death for Epilepsy (SUDEP).

Prevalence and Incidence of Drug-Resistant Temporal Lobe Epilepsy in Qatar

Background:

Information on the epidemiology of temporal lobe epilepsy associated with hippocampal sclerosis (TLE-HS) from Qatar and the developing countries is scarce. To acquire knowledge on the incidence and prevalence of drug-resistant TLE-HS in Qatar, we designed this analytical and extrapolative systematic review of the existing literature.

Material and methods:

We searched the electronic database PubMed from 1947 until April, 2018, using the following search terms in the title: “epilepsy” OR “temporal lobe” OR “hippocampal sclerosis” AND “epidemiology” OR “incidence” OR “prevalence.” Relevant original studies, reviews, and their references, were included. We extrapolated from the previous international literature to estimate the epidemiology of drug-resistant TLE-HS in Qatar.

Results:

The estimated Qatar incidence of epilepsy varies from 50 to 61 per 100 000 persons per year, and the estimated prevalence of epilepsy is 6.54 per 1000 population; the estimated incidence of TLE varies from 9.5 to 11.6 patients per 100 000 population per year and the estimated prevalence of TLE is 1.76 patients per 1000 people, with 4721 patients having TLE in Qatar. Finally, the reviewed studies also helped in making an estimate of the Qatar prevalence of drug-resistant TLE-HS to be between 0.3 and 0.6 cases per 1000 people (804-1609 current patients) and the Qatar incidence of drug-resistant TLE-HS (2.3-4.3 cases per 100 000 people, per year) with 62 to 116 new patients per year.

Conclusion:

Our study suggests that 804 to 1609 current patients (with 62-116 additional patients per year) in Qatar are suffering from drug-resistant TLE-HS; emphasis should be placed on the surgical aspect of the current Qatar Comprehensive Epilepsy Program.

Aberrant expression of PAR bZIP transcription factors is associated with epileptogenesis, focus on hepatic leukemia factor

Epilepsy is a widespread neurological disease characterized by abnormal neuronal activity resulting in recurrent seizures. There is mounting evidence that a circadian system disruption, involving clock genes and their downstream transcriptional regulators, is associated with epilepsy. In this study, we characterized the hippocampal expression of clock genes and PAR bZIP transcription factors (TFs) in a mouse model of temporal lobe epilepsy induced by intrahippocampal injection of kainic acid (KA). The expression of PAR bZIP TFs was significantly altered following KA injection as well as in other rodent models of acquired epilepsy. Although the PAR bZIP TFs are regulated by proinflammatory cytokines in peripheral tissues, we discovered that the regulation of their expression is inflammation-independent in hippocampal tissue and rather mediated by clock genes and hyperexcitability. Furthermore, we report that hepatic leukemia factor (Hlf), a member of PAR bZIP TFs family, is invariably downregulated in animal models of acquired epilepsy, regulates neuronal activity in vitro and its overexpression in dentate gyrus neurons in vivo leads to altered expression of genes associated with seizures and epilepsy. Overall, our study provides further evidence of PAR bZIP TFs involvement in epileptogenesis and points to Hlf as the key player.

Prevention and treatment of temporal lobe epilepsy: lessons from hepatitis B story!

Temporal lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and hippocampal sclerosis (HS) is the most common pathological substrate of TLE. Considering the significant consequences of uncontrolled seizures (e.g. increased morbidity and mortality), epilepsy prevention remains a necessity that potentially could save many lives. Human herpes virus-6 (HHV-6) has been linked to TLE in humans. The relationship between HHV-6 and HS-TLE could be attributed to a neuro-inflammatory cascade triggered by the infection, involving direct neuronal damage and production of several pro-inflammatory cytokines under certain conditions that are still incompletely understood. Hepatitis B virus (HBV) infection is another chronic viral infection with a life-long latency. HBV infection is linked to various clinical conditions, including liver cirrhosis. There are currently three ways to fight HBV infection and its consequences; primary prevention (by vaccination), secondary prevention (by drug therapy), and tertiary prevention (by liver transplantation). Considering the similarities between the natural histories of HHV-6 and HBV infections, and also the successful strategies which are currently available to fight HBV infection and its long-term consequences, here, we propose three strategies to fight HHV-6 and its possible long-term consequence (i.e. HS-TLE): Primary prevention: by developing vaccines to prevent HHV-6 infection; Secondary prevention: by considering trials of antiviral drugs to treat HHV-6 infection, when it happens in the childhood to hopefully prevent its long-term consequences; and, Tertiary prevention: by stem cell therapy for drug-resistant epilepsy.

Neuropsychologic assessment

The purpose of a pediatric neuropsychologic assessment is to evaluate cognitive, behavioral, sensory-motor, perceptual, and socioaffective functioning. A standardized, validated set of tools, questionnaires, and qualitative methods is applied to this end. The neuropsychologist integrates the results of the formal assessment, the case history, and third-party observations to interpret the individual findings across disciplines and draw conclusions about brain-behavior relationships. Various indications for neuropsychologic assessment include the identification of neurodevelopmental difficulties and the characterization of the impact of medical conditions or a pharmaceutical treatment. Prior to the evaluation, as much information as possible must be gathered about the child for efficient and accurate planning. In the context of pediatric neuropsychologic assessments, special challenges requiring more flexibility as regards the duration of the assessment, the use of different age-specific tools, or particular sensitivity when interacting with the child may arise. Neuropsychologic assessment is a cornerstone in the process of diagnosing neurodevelopmental disabilities in children and is frequently a component of a multidisciplinary evaluation. From it can be derived recommendations for the different contexts of a child's life (e.g., family, care team, school).

Predictors of meaningful improvement in quality of life after selective amygdalohippocampectomy in Chinese patients with refractory temporal lobe epilepsy: A prospective study

PURPOSE

Our aim was to determine the independent predictors of minimum clinically important difference (MCID) in quality of life (QOL) after selective amygdalohippocampectomy (SAH) among Chinese patients with refractory mesial temporal lobe epilepsy (MTLE).

METHODS

We conducted a prospective study and enrolled 50 consecutive patients with refractory MTLE who underwent SAH after their presurgical evaluations. The variables independently associated with MCID in the Quality of Life in Epilepsy Inventory-31 (QOLIE-31) overall score 1 year after SAH were analyzed by multiple binary logistic regression analysis.

RESULTS

Significant improvements in the QOLIE-31 overall score and all subscale scores were observed after SAH (p < 0.001). Among 50 patients with refractory MTLE, 78% reached the criteria for MCID of QOL overall score after SAH. In the multiple binary logistic regression model, the presurgical independent predictors of significant improvement by MCID in QOL were absence of depression diagnosis (adjusted odds ratio [OR] = 8.391, 95% confidence interval [CI] = 1.240-56.776, p = 0.029) and good cognitive function (adjusted OR = 8.427, 95% CI = 1.115-63.670, p = 0.039); the postoperative independent predictor was seizure freedom (adjusted OR = 8.477, 95% CI = 1.195-60.122, p = 0.032). The sensitivity and specificity for significant improvement in the QOL were 97.4% and 45.5% respectively, with an overall model accuracy of 86.0%.

CONCLUSIONS

Presurgical depression, cognitive function, and postsurgical seizure freedom are independent predictors for meaningful improvement in QOL after SAH among the Chinese patients with refractory MTLE. Preoperative evaluation of patients with refractory MTLE should consider the cognitive dysfunction and psychological disorders.

Photobiomodulation as a treatment for neurodegenerative disorders: current and future trends

Photobiomodulation (PBM) is a rapidly growing as an innovative therapeutic modality for various types of diseases in recent years. Neuronal degeneration is irreversible process and it is proven to be difficult to slow down or stop the progression. Pharmacologic approaches to slow neuronal degeneration have been studied, but are limited due to concerns about the side effects. Therefore, it is necessary to develop a new therapeutic approach to stabilize neuronal degeneration and achieve neuronal protection against several neurodegenerative diseases. In this review, we have introduced several previous studies showing the positive effect of PBM over neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and different types of epilepsy. Despite excellent outcomes of animal researches, not many clinical studies are conducted or showed positive outcome of PBM against neurodegenerative disease. To achieve clinical application of PBM against neurodegenerative disorder, determination of exact mechanism and establishment of effective clinical protocol seems to be necessary.

Neuroimaging correlates of language network impairment and reorganization in temporal lobe epilepsy

Advanced, noninvasive imaging has revolutionized our understanding of language networks in the brain and is reshaping our approach to the presurgical evaluation of patients with epilepsy. Functional magnetic resonance imaging (fMRI) has had the greatest impact, unveiling the complexity of language organization and reorganization in patients with epilepsy both pre- and postoperatively, while volumetric MRI and diffusion tensor imaging have led to a greater appreciation of structural and microstructural correlates of language dysfunction in different epilepsy syndromes. In this article, we review recent literature describing how unimodal and multimodal imaging has advanced our knowledge of language networks and their plasticity in epilepsy, with a focus on the most frequently studied epilepsy syndrome in adults, temporal lobe epilepsy (TLE). We also describe how new analytic techniques (i.e., graph theory) are leading to a refined characterization of abnormal brain connectivity, and how subject-specific imaging profiles combined with clinical data may enhance the prediction of both seizure and language outcomes following surgical interventions.

[Patterns of brain functional connectivity in frontal and temporal lobe epilepsies]

AIM

To examine alterations of functional connectivity (FC) of the brain in patients with frontal and temporal lobe epilepsies.

MATERIAL AND METHODS

Forty-three patients, aged 18-55 years, including 32 with temporal lobe epilepsy (TLE) and 11 with frontal lobe epilepsy (FLE), and 32 age/gender-matched healthy controls (HC) underwent structural and functional MRI on 1,5 T scanner. Imaging data were further analysed for functional connectivity characteristics by seed-based and ICA analyses.

RESULTS

Most prominent in the TLE group, was a decrease in FC of insula and peri-insular cortical regions compared to HC. These alterations of FC in left-side TLE were significant on the left. An increase of FC between dorsal part of attention resting network and regions of temporal and parietal cortices characterized right-side TLE. In addition, TLE group had decreased FC between anterior cingulate and basal ganglia. All the significant alterations of FC in FLE related to increased FC in patients compared to HC. FC of temporal regions was altered to a greater extent.

CONCLUSION

Localization and lateralization of seizure focus determines the alterations of brain FC in patients with focal epilepsy.

Imaging episodic memory during development and childhood epilepsy

Epilepsy affects 2.2 million adults in the USA, with 1 in 26 people developing epilepsy at some point in their lives. Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy as medial structures, and the hippocampus in particular, are prone to generating seizures. Selective anterior temporal resection (which removes the hippocampus) is the most effective intractable TLE treatment, but given the critical role of the mesial temporal lobe in memory functioning, resection can have negative effects on this crucial cognitive skill. To minimize the adverse impact of temporal lobe surgery on memory functioning, reliable pre-surgical guides are needed. Clinical functional magnetic resonance imaging (fMRI) provides reliable, noninvasive guidance of language functioning and plays a growing role in the pre-surgical evaluation for epilepsy patients; however, localization of memory function in children with epilepsy using fMRI has not been established. Aside from the lack of neuroimaging memory studies in children with TLE, studies of typical development are limited. This review will focus on the functional anatomy of memory systems throughout development, with a focus on TLE. TLE provides the ideal model from which to understand memory function and the limits of plasticity and compensation/reorganization throughout development.

Evaluation of dual pathology among drug-resistant epileptic patients with hippocampal sclerosis

PURPOSE

Dual pathology (DP) is defined as simultaneous presence of hippocampal sclerosis (HS) and any other pathology in the brain. Since this is a less probed concept, we aimed to evaluate the frequency and characteristics of DP among drug-resistant epileptic patients with HS.

METHODS

This is a cross-sectional study conducted during 2007-2016 in Kashani Comprehensive Epilepsy Center, Isfahan, Iran. Patients with diagnosis of drug-resistant epilepsy and HS were enrolled in the study, and demographic data, seizure semiology, EEG findings, and MRI findings were collected. We compared these variables between three groups of DP, unilateral HS, and bilateral HS.

RESULTS

Of the 200 enrolled cases, 29 patients (14.5%) had DP and 21 patients (10.5%) had bilateral HS; the remaining patients had unilateral HS. The average age of patients with DP was 30.03, and 65.5% of them were male. Patients with DP had more EEG discharges from regional and multi-focal sites compared to unilateral HS (P value < 0.001). Also, complex partial seizure (CPS) was more commonly presented in patients with unilateral HS (96.8%). Comparison of disease characteristics between DP and bilateral HS showed no difference in most categories (P > 0.05).

CONCLUSIONS

We found DP among 14.5% of our drug-resistant epileptic patients with HS. DP patients mostly presented with CPS and had high proportion of ictal and interictal EEG discharges from regional and multi-focal areas. Gliosis and focal cortical dysplasia were the most common pathologies among DP patients. Patients with DP showed a similar behavior to bilateral HS in many features.

Resting state functional connectivity patterns associated with pharmacological treatment resistance in temporal lobe epilepsy

There are no functional imaging based biomarkers for pharmacological treatment response in temporal lobe epilepsy (TLE). In this study, we investigated whether there is an association between resting state functional brain connectivity (RsFC) and seizure control in TLE. We screened a large database containing resting state functional magnetic resonance imaging (Rs-fMRI) data from 286 epilepsy patients. Patient medical records were screened for seizure characterization, EEG reports for lateralization and location of seizure foci to establish uniformity of seizure localization within patient groups. Rs-fMRI data from patients with well-controlled left TLE, patients with treatment-resistant left TLE, and healthy controls were analyzed. Healthy controls and cTLE showed similar functional connectivity patterns, whereas trTLE exhibited a significant bilateral decrease in thalamo-hippocampal functional connectivity. This work is the first to demonstrate differences in neural network connectivity between well-controlled and treatment-resistant TLE. These differences are spatially highly focused and suggest sites for the etiology and possibly treatment of TLE. Altered thalamo-hippocampal RsFC thus is a potential new biomarker for TLE treatment resistance.

Anticonvulsant effect of dipropofol by enhancing native GABA currents in cortical neurons in mice

Temporal lobe epilepsy (TLE), the most common pharmacoresistant focal epilepsy disorder, remains a major unmet medical need. Propofol is used as a short-acting medication for general anesthesia and refractory status epilepticus with issues of decreased consciousness and memory loss. Dipropofol, a derivative of propofol, has been reported to exert antioxidative and antibacterial activities. Here we report that dipropofol exerted anticonvulsant activity in a mouse model of kainic acid-induced seizures. Whole cell patch-clamp recordings of brain slices from the medial entorhinal cortex (mEC) revealed that dipropofol hyperpolarized the resting membrane potential and reduced the number of action potential firings, resulting in suppression of cortical neuronal excitability. Furthermore, dipropofol activated native tonic GABAA currents of mEC layer II stellate neurons in a dose-dependent manner with an EC50 value of 9.3 ± 1.6 μM (mean ± SE). Taken together, our findings show that dipropofol activated GABAA currents and exerted anticonvulsant activities in mice, thus possessing developmental potential for new anticonvulsant therapy.

NEW & NOTEWORTHY The anticonvulsant effect of dipropofol was shown in a mouse model of kainic acid-induced seizures. Whole cell patch-clamp recordings of brain slices showed suppression of cortical neuronal excitability by dipropofol. Dipropofol activated the native tonic GABAA currents in a dose-dependent manner.

Deep learning applied to whole-brain connectome to determine seizure control after epilepsy surgery

OBJECTIVE

We evaluated whether deep learning applied to whole-brain presurgical structural connectomes could be used to predict postoperative seizure outcome more accurately than inference from clinical variables in patients with mesial temporal lobe epilepsy (TLE).

METHODS

Fifty patients with unilateral TLE were classified either as having persistent disabling seizures (SZ) or becoming seizure-free (SZF) at least 1 year after epilepsy surgery. Their presurgical structural connectomes were reconstructed from whole-brain diffusion tensor imaging. A deep network was trained based on connectome data to classify seizure outcome using 5-fold cross-validation.

RESULTS

Classification accuracy of our trained neural network showed positive predictive value (PPV; seizure freedom) of 88 ± 7% and mean negative predictive value (NPV; seizure refractoriness) of 79 ± 8%. Conversely, a classification model based on clinical variables alone yielded <50% accuracy. The specific features that contributed to high accuracy classification of the neural network were located not only in the ipsilateral temporal and extratemporal regions, but also in the contralateral hemisphere.

SIGNIFICANCE

Deep learning demonstrated to be a powerful statistical approach capable of isolating abnormal individualized patterns from complex datasets to provide a highly accurate prediction of seizure outcomes after surgery. Features involved in this predictive model were both ipsilateral and contralateral to the clinical foci and spanned across limbic and extralimbic networks.

Cannabidiol exerts antiepileptic effects by restoring hippocampal interneuron functions in a temporal lobe epilepsy model

Background and Purpose

A non‐psychoactive phytocannabinoid, cannabidiol (CBD), shows promising results as an effective potential antiepileptic drug in some forms of refractory epilepsy. To elucidate the mechanisms by which CBD exerts its anti‐seizure effects, we investigated its effects at synaptic connections and on the intrinsic membrane properties of hippocampal CA1 pyramidal cells and two major inhibitory interneurons: fast spiking, parvalbumin (PV)‐expressing and adapting, cholecystokinin (CCK)‐expressing interneurons. We also investigated whether in vivo treatment with CBD altered the fate of CCK and PV interneurons using immunohistochemistry.

Experimental Approach

Electrophysiological intracellular whole‐cell recordings combined with neuroanatomy were performed in acute brain slices of rat temporal lobe epilepsy in in vivo (induced by kainic acid) and in vitro (induced by Mg²⁺‐free solution) epileptic seizure models. For immunohistochemistry experiments, CBD was administered in vivo (100 mg·kg⁻¹) at zero time and 90 min post status epilepticus, induced with kainic acid.

Key Results

Bath application of CBD (10 μM) dampened excitability at unitary synapses between pyramidal cells but enhanced inhibitory synaptic potentials elicited by fast spiking and adapting interneurons at postsynaptic pyramidal cells. Furthermore, CBD restored impaired membrane excitability of PV, CCK and pyramidal cells in a cell type‐specific manner. These neuroprotective effects of CBD were corroborated by immunohistochemistry experiments that revealed a significant reduction in atrophy and death of PV‐ and CCK‐expressing interneurons after CBD treatment.

Conclusions and Implications

Our data suggest that CBD restores excitability and morphological impairments in epileptic models to pre‐epilepsy control levels through multiple mechanisms to reinstate normal network function.

Racial disparities in temporal lobe epilepsy

OBJECTIVE

This study reports on epilepsy type period prevalence and black-white racial differences in a large patient population in the Southeastern United States.

METHODS

For all patients visiting the University of Alabama at Birmingham's seizure monitoring unit between 2000 and 2011 (n = 3240), video EEG diagnosis was recorded along with basic demographic information. Descriptive statistics and multivariate logistic regression were used to identify factors associated with temporal lobe epilepsy (TLE) diagnosis.

RESULTS

The racial distribution was 77.3% white, and 20.0% black (other races were only 2.3% of the population). Most patients had either TLE (n = 630) or PNES (n = 1150) compared to other focal (n = 424) or generalized epilepsies (n = 224). The diagnosis of TLE was significantly greater for blacks than whites (odds ratio [OR] = 1.87, 95% confidence interval [CI] 1.47-2.37). The period prevalence measures for the other conclusively diagnosed epilepsies were not significantly different. Women were disproportionately represented in the study population, and black women carried the most statistical weight for the TLE prevalence difference.

INTERPRETATION

The nearly two-fold larger period prevalence of TLE among black patients is a striking finding that merits explanation. Although some selection bias exists due to a moderately lower than expected representation of blacks, socioeconomic status or access to care should not be assumed to be the only factors that might be responsible for the prevalence difference. Rather, all clues for distinct pathophysiological racial differences should be explored.

Neuropsychological outcomes following paediatric temporal lobe surgery for epilepsies: Evidence from a systematic review

OBJECTIVE

The systematic review aimed to assess the neuropsychological outcomes of temporal lobe resections for epilepsy in children. Additional objectives included determining whether earlier age at surgery leads to better neuropsychological outcomes; the relationships between and predictors of these outcomes.

METHODS

Using advanced search terms, a systematic review of electronic databases was conducted, comprising MEDLINE, Embase, PsycINFO, Global Health, Web of Science and CINAHL. Included studies reported on outcome following neurosurgical treatment for epilepsy. Specifically, studies were included if they reported neuropsychological outcomes and were concerned only with temporal lobe resection.

RESULTS

73 studies met inclusion criteria. For reported neuropsychological outcomes, the majority of participants remained stable after surgery; some declined and some improved. There was some evidence for increased material-specific memory deficits after temporal lobe surgery based on resection side, and more positive cognitive outcome for those with lower pre-surgical ability level.

SIGNIFICANCE

Retrieved evidence highlights the need for improvements to quality of methodology and reporting. Appropriately designed prospective multicentre trials should be conducted with adequate follow-up for long-term outcomes to be measured. Core outcome measures should be agreed between centres. This would permit higher quality evidence so that clinicians, young people and their families may make better informed decisions about whether or not to proceed with surgery and likely post-operative profile.

Involvement of fast-spiking cells in ictal sequences during spontaneous seizures in rats with chronic temporal lobe epilepsy

See Lenck-Santini (doi:10.1093/awx205) for a scientific commentary on this article. Epileptic seizures represent altered neuronal network dynamics, but the temporal evolution and cellular substrates of the neuronal activity patterns associated with spontaneous seizures are not fully understood. We used simultaneous recordings from multiple neurons in the hippocampus and neocortex of rats with chronic temporal lobe epilepsy to demonstrate that subsets of cells discharge in a highly stereotypical sequential pattern during ictal events, and that these stereotypical patterns were reproducible across consecutive seizures. In contrast to the canonical view that principal cell discharges dominate ictal events, the ictal sequences were predominantly composed of fast-spiking, putative inhibitory neurons, which displayed unusually strong coupling to local field potential even before seizures. The temporal evolution of activity was characterized by unique dynamics where the most correlated neuronal pairs before seizure onset displayed the largest increases in correlation strength during the seizures. These results demonstrate the selective involvement of fast spiking interneurons in structured temporal sequences during spontaneous ictal events in hippocampal and neocortical circuits in experimental models of chronic temporal lobe epilepsy.

DETERMINATES CLÍNICOS EN LA MEMORIA AUTOBIOGRÁFICA DE PACIENTES CON EPILEPSIA DEL LÓBULO TEMPORAL

Introducción. El paciente con epilepsia del lóbulo temporal presenta generalmente una enfermedad de difícil manejo, y la enfermedad cursa con alteraciones en memoria autobiográfica. Sin embargo, la epilepsia es una enfermedad en la que actúan diversos factores clínicos que contribuyen a determinar la severidad y el pronóstico de la enfermedad. Objetivo. Explorar la posible relación entre el rendimiento de los pacientes con epilepsia del lóbulo temporal con esclerosis hipocampal en memoria autobiográfica y las variables clínicas asociadas. Pacientes y métodos. La muestra estuvo conformada por 25 pacientes con diagnóstico de epilepsia del lóbulo temporal. Se les suministró la Entrevista de Memoria Autobiográfica para valorar el desempeño en memoria personal semántica e incidentes autobiográficos. Se determinó la relación entre el rendimiento en memoria autobiográfica y variables clínicas asociadas como edad de inicio, número de años con epilepsia, lateralización de la zona de inicio ictal, refractariedad al tratamiento, tipo de terapia farmacológica y número de medicamentos. Para determinar las correlaciones se calculó el coeficiente de correlación de Spearman, mientras que para la comparación entre grupos se utilizó la prueba U de Mann-Whitney. Resultados. Variables clínicas como el tiempo de la evolución de la enfermedad, refractariedad al tratamiento, empleo de politerapia y número de medicamentos, afectan el desempeño en memoria autobiográfica en pacientes con epilepsia del lóbulo temporal. Conclusiones. Si bien, la epilepsia del lóbulo temporal general alteraciones en la memoria autobiográfica, diversas variables clínicas asociadas a la enfermedad, afectan aún más la capacidad mnésica de los pacientes.

Mesial temporal lobe epilepsy with childhood febrile seizure

OBJECTIVES

To evaluate the demographic and clinical manifestations of patients with mesial temporal sclerosis and temporal lobe epilepsy (MTS-TLE) with childhood febrile seizure (FS) and establishing the potential differences as compared to those without FS. We also investigated the surgery outcome in these two groups of patients.

MATERIALS AND METHODS

In this retrospective study, all patients with a clinical diagnosis of drug-resistant TLE due to mesial temporal sclerosis, who underwent epilepsy surgery at Jefferson Comprehensive Epilepsy Center, were recruited. Patients were prospectively registered in a database from 1986 through 2014. Postsurgical outcome was classified into two groups; seizure-free or relapsed. Clinical manifestations and outcome were compared between patients with MTS-TLE with FS and those without FS.

RESULTS

Two hundred and sixty-two patients were eligible for this study. One hundred and seventy patients (64.9%) did not have FS in their childhood, while 92 patients (35.1%) reported experiencing FS in their childhood. Demographic and clinical characteristics of these two groups of patients were not different. Postoperative seizure outcome was not statistically different between these two groups of patients (P = 0.19).

CONCLUSIONS

When MTS is the pathological substrate of TLE, clinical manifestations and response to surgical treatment of patients are very similar in patients with history of febrile seizure in their childhood compared to those without such an experience. In other words, when the subgroup of patients with MTS-TLE and drug-resistant seizures is examined history of childhood febrile seizure loses its value as a distinguishing factor in characteristics or predictive factor for surgery outcome.

Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients

Approximately 30% of epilepsy patients are refractory to antiepileptic drugs. In these cases, surgery is the only alternative to eliminate/control seizures. However, a significant minority of patients continues to exhibit post-operative seizures, even in those cases in which the suspected source of seizures has been correctly localized and resected. The protocol presented here combines a clinical procedure routinely employed during the pre-operative evaluation of temporal lobe epilepsy (TLE) patients with a novel technique for network analysis. The method allows for the evaluation of the temporal evolution of mesial network parameters. The bilateral insertion of foramen ovale electrodes (FOE) into the ambient cistern simultaneously records electrocortical activity at several mesial areas in the temporal lobe. Furthermore, network methodology applied to the recorded time series tracks the temporal evolution of the mesial networks both interictally and during the seizures. In this way, the presented protocol offers a unique way to visualize and quantify measures that considers the relationships between several mesial areas instead of a single area.