Characteristics of medial temporal lobe epilepsy: II. Interictal and ictal scalp electroencephalography, neuropsychological testing, neuroimaging, surgical results, and pathology

Left-sided epileptiform activity influences language lateralization in right mesial temporal sclerosis

OBJECTIVE

To investigate the association between left epileptiform activity and language laterality indices (LI) in patients with right mesial temporal sclerosis (MTS).

METHODS

Twenty-two patients with right MTS and 22 healthy subjects underwent fMRI scanning while performing a language task. LI was calculated in multiple regions of interest (ROI). Data on the presence of left epileptiform abnormalities were obtained during prolonged video-EEG monitoring.

RESULTS

After correction for multiple comparisons, LI was reduced in the middle temporal gyrus in the left interictal epileptiform discharges (IED+) group, compared with the left IED- group (p < 0.05).

SIGNIFICANCE

Using a responsive reading naming fMRI paradigm, right MTS patients who presented left temporal interictal epileptiform abnormalities on video-EEG showed decreased LI in the middle temporal gyrus, indicating decreased left middle temporal gyrus activation, increased right middle temporal gyrus activation or a combination of both, demonstrative of language network reorganization, specially in the MTG, in this patient population.

PLAIN LANGUAGE SUMMARY

This research studied 22 patients with right mesial temporal sclerosis (a specific type of epilepsy) comparing them to 22 healthy individuals. Participants were asked to perform a language task while undergoing a special brain imaging technique (fMRI). The findings showed that patients with epilepsy displayed a change in the area of the brain typically responsible for language processing. This suggests that their brains may have adapted due to their condition, altering the way language is processed.

Yield of video electro encephalography for phase 1 pre-surgical evaluation of drug resistant epilepsy in 1200 adults: retrospective study from a tertiary center situated in a lower-middle-income country

INTRODUCTION

Video Electroencephalography (VEEG) is crucial for presurgical evaluation of Drug Refractory Epilepsy (DRE). The yield of VEEG in large volume centers, particularly those situated in Low-and Middle-Income countries (LMIC) is not well studied.

METHODOLOGY

We studied 1200 adults with drug resistant focal epilepsy whose seizures were recorded during VEEG in the epilepsy monitoring unit. VEEG review and analysis was done independently by trained epileptologists. Video EEG and MRI data were examined for concordance in order to generate a hypothesis for the presumed epileptogenic zone.

RESULTS

Analysis of seizure semiology provided information on the symptomatogenic zone in most cases except for 33 (2.75%) patients. A total of 1050 (87.5%) patients showed interictal epileptiform discharges (IEDs) with most (58.3%) showing unilateral IEDs. Most patients (n = 1162, 96.83%) showed ictal EEG discharges of which 951(81.8%) had unilateral ictal onset. Abnormal MRI was seen in 978 (81.5%) patients. Concordance of electroclinical data obtained by analysis of VEEG with MRI abnormality could be established in most patients (63%). Concordance was higher for patients with ictal onset from temporal regions (83.71%) as compared to posterior cortex (55.4%) and frontal regions (43.5%.) CONCLUSION: This study highlights the high yield of VEEG in phase 1 presurgical evaluation in DRE. Systematic evaluation of data from VEEG provided lateralizing and localizing information in most cases. Concordance between VEEG and MRI findings was noted in most patients. These findings support steps to increase referral for pre-surgical evaluation in DRE.

Ipsilateral preictal alpha rhythm attenuation (IPARA): An EEG sign of side of seizure onset in temporal lobe epilepsy

PURPOSE

Identification of the seizure onset zone is critically important for outlining the surgical plan in the treatment of pharmacoresistant focal epilepsy. In patients with temporal lobe epilepsy (TLE), bilateral ictal scalp EEG changes frequently occur and can make lateralization of the seizure onset zone difficult. We investigated the incidence and clinical utility of unilateral preictal alpha rhythm attenuation as a lateralizing sign of seizure onset in TLE.

METHODS

Scalp EEG recordings of the seizures acquired during presurgical video-EEG monitoring of 57 consecutive patients with TLE were reviewed retrospectively. Included patients had interictal baseline recordings demonstrating symmetrical posterior alpha rhythm and seizures occurring during wakefulness.

RESULTS

We identified a total of 649 seizures in the 57 patients, of which 448 seizures in 53 patients fulfilled the inclusion criteria. Among the 53 included patients, 7 patients (13.2%) exhibited a distinct attenuation of the posterior alpha rhythm prior to the first ictal EEG changes, in 26 of 112 (23.2%) included seizures. Preictal alpha rhythm attenuation in these seizures was ipsilateral to the ultimately determined side of seizure onset (based on video-EEG or intracranial EEG findings) in 22 (84.6%) of these seizures and bilateral in 4 (15.4%), and occurred on average 5.9 ± 2.6 s prior to ictal EEG onsets.

CONCLUSION

Our findings suggest that in some patients with TLE lateralized preictal attenuation of the posterior alpha rhythm may be a useful indicator of side of seizure onset, presumably due to early disruption of thalamo-temporo-occipital network function, likely mediated through the thalamus.

A rare case of drug sensitive adult‐onset temporal lobe epilepsy due to a focal cortical dysplasia revealed by ictal coughing: First report in sub‐Saharan Africa

This case suggests that clinicians should consider seizures as a differential diagnosis of paroxystic cough with loss of consciousness. Focal cortical dysplasia should equally be screened for with magnetic resonance imaging (MRI) scans even in adults with epilepsy in sub‐Saharan Africa.

This case suggests that clinicians should consider seizures as a differential diagnosis of paroxystic cough with loss of consciousness. Focal cortical dysplasia should equally be screened for with Magnetic Resonance Imaging (MRI) scans even in adults with epilepsy in sub‐Saharan Africa.

Deep learning for the diagnosis of mesial temporal lobe epilepsy

OBJECTIVE

This study aimed to enable the automatic detection of the hippocampus and diagnose mesial temporal lobe epilepsy (MTLE) with the hippocampus as the epileptogenic area using artificial intelligence (AI). We compared the diagnostic accuracies of AI and neurosurgical physicians for MTLE with the hippocampus as the epileptogenic area.

METHOD

In this study, we used an AI program to diagnose MTLE. The image sets were processed using a code written in Python 3.7.4. and analyzed using Open Computer Vision 4.5.1. The deep learning model, which was a fine-tuned VGG16 model, consisted of several layers. The diagnostic accuracies of AI and board-certified neurosurgeons were compared.

RESULTS

AI detected the hippocampi automatically and diagnosed MTLE with the hippocampus as the epileptogenic area on both T2-weighted imaging (T2WI) and fluid-attenuated inversion recovery (FLAIR) images. The diagnostic accuracies of AI based on T2WI and FLAIR data were 99% and 89%, respectively, and those of neurosurgeons based on T2WI and FLAIR data were 94% and 95%, respectively. The diagnostic accuracy of AI was statistically higher than that of board-certified neurosurgeons based on T2WI data (p = 0.00129).

CONCLUSION

The deep learning-based AI program is highly accurate and can diagnose MTLE better than some board-certified neurosurgeons. AI can maintain a certain level of output accuracy and can be a reliable assistant to doctors.

De novo epilepsy after microsurgical resection of brain arteriovenous malformations

OBJECTIVE

Seizures are the second most common presenting symptom of brain arteriovenous malformations (bAVMs) after hemorrhage. Risk factors for preoperative seizures and subsequent seizure control outcomes have been well studied. There is a paucity of literature on postoperative, de novo seizures in initially seizure-naïve patients who undergo resection. Whereas this entity has been documented after craniotomy for a wide variety of neurosurgically treated pathologies including tumors, trauma, and aneurysms, de novo seizures after bAVM resection are poorly studied. Given the debilitating nature of epilepsy, the purpose of this study was to elucidate the incidence and risk factors associated with de novo epilepsy after bAVM resection.

METHODS

A retrospective review of patients who underwent resection of a bAVM over a 15-year period was performed. Patients who did not present with seizure were included, and the primary outcome was de novo epilepsy (i.e., a seizure disorder that only manifested after surgery). Demographic, clinical, and radiographic characteristics were compared between patients with and without postoperative epilepsy. Subgroup analysis was conducted on the ruptured bAVMs.

RESULTS

From a cohort of 198 patients who underwent resection of a bAVM during the study period, 111 supratentorial ruptured and unruptured bAVMs that did not present with seizure were included. Twenty-one patients (19%) developed de novo epilepsy. One-year cumulative rates of developing de novo epilepsy were 9% for the overall cohort and 8.5% for the cohort with ruptured bAVMs. There were no significant differences between the epilepsy and no-epilepsy groups overall; however, the de novo epilepsy group was younger in the cohort with ruptured bAVMs (28.7 ± 11.7 vs 35.1 ± 19.9 years; p = 0.04). The mean time between resection and first seizure was 26.0 ± 40.4 months, with the longest time being 14 years. Subgroup analysis of the ruptured and endovascular embolization cohorts did not reveal any significant differences. Of the patients who developed poorly controlled epilepsy (defined as Engel class III–IV), all had a history of hemorrhage and half had bAVMs located in the temporal lobe.

CONCLUSIONS

De novo epilepsy after bAVM resection occurs at an annual cumulative risk of 9%, with potentially long-term onset. Younger age may be a risk factor in patients who present with rupture. The development of poorly controlled epilepsy may be associated with temporal lobe location and a delay between hemorrhage and resection.

Correlation Between Ictal Signs and Anatomical Subgroups in Temporal Lobe Seizures: A Stereoelectroencephalography Study

Objective

Ictal semiology is a fundamental part of the presurgical evaluation of patients with temporal lobe epilepsy. We aimed to identify different anatomical and semiologic subgroups in temporal lobe seizures, and investigate the correlation between them.

Methods

We enrolled 93 patients for whom stereoelectroencephalography exploration indicated that the seizure-onset zone was within the temporal lobe. Ictal signs and concomitant stereoelectroencephalography changes were carefully reviewed and quantified, and then cluster analysis and the Kendall correlation test were used to associate ictal signs with the temporal structures of patients.

Results

Clustering analysis identified two main groups of temporal structures. Group 1 consisted of the medial temporal lobe structures and the temporal pole, which were divided into two subgroups. Group 1A included the hippocampal head, hippocampal body, and amygdala, and this subgroup correlated significantly with oroalimentary automatisms, feeling of fear, and epigastric auras. Group 1B included the hippocampal tail, temporal pole, and parahippocampal gyrus, and this subgroup correlated significantly with manual and oroalimentary automatisms. Group 2 consisted of the cortical structures of the temporal lobe and was also divided into two subgroups. Group 2A included the superior and middle temporal gyrus, correlated significantly with bilateral rictus/facial contraction, generalized tonic-clonic seizure, and manual automatisms. Group 2B included Heschl's gyrus, the inferior temporal gyrus, and the fusiform gyrus, and this subgroup correlated significantly with auditory auras, focal hypokinetics, unilateral upper and lower limbs tonic posture/clonic signs, head/eye deviation, unilateral versive signs, and generalized tonic-clonic seizure.

Significance

The temporal structures can be categorized according to the level at which each structure participates in seizures, and different anatomical subgroups can be correlated with different ictal signs. Identifying specific semiologic features can help us localize the epileptogenic zone and thus develop stereoelectroencephalography electrode implantation and surgical resection protocols for patients with temporal lobe epilepsy.

Changes of oxygen saturation in patients with pure temporal lobe epilepsy

PURPOSE

Ictal hypoxemia is accepted as one of the mechanisms underlying sudden unexpected death in epilepsy (SUDEP). Although ictal hypoxemia is more common in generalized seizures, it also occurs in focal seizures with or without generalization. In this study, we aimed to show the relationship between clinical and electroencephalographic findings of seizures in patients with temporal lobe epilepsy (TLE) with periictal oxygen saturation.

METHODS

The data of 55 adult patients who were hospitalized in the Video EEG Monitoring Unit (VEMU) and operated on for drug-resistant TLE between January 2017 and December 2020 were examined. Forty-five seizures from 21 patients with ictal peripheral arterial saturation information and that were seizure-free for at least a year during the follow-up were included in the study.

RESULTS

The median patient age was 28 (IQR 25-39.5) years (women: 9, men: 12). Age at epilepsy onset was negatively correlated with saturation at seizure onset. Moreover, the age at VEMU admission was also negatively correlated with saturation at seizure onset and the lowest levels of saturation. The saturation at the end of the seizures and the lowest saturation measured in the periictal period with generalization of EEG were significantly lower than those without generalization. The onset of ictal EEG with the rhythmic theta pattern was significantly associated with the lowest level of saturation (<90%), postictal generalized electroencephalographic suppression (PGES), and the presence of generalization.

CONCLUSION

According to the study, rhythmic ictal theta activity, older age, nocturnal seizure, and generalization in ictal EEG might increase the potential risk of SUDEP. Further studies including a greater number of subjects and different epilepsy syndromes may provide more comprehensive information about potential biomarkers for SUDEP.

Localizing and Lateralizing Value of Seizure Onset Pattern on Surface EEG in FCD Type II

BACKGROUND

Surface ictal electroencephalographic (EEG) monitoring has an important role in the presurgical evaluation of patients with focal cortical dysplasia (FCD). This study aimed to examine the characteristics of seizure onset pattern (SOP) on surface ictal EEG. This information will be useful for invasive monitoring planning.

METHODS

We reviewed 290 seizures from 31 patients with intractable seizures related to FCD type II (6 patients with FCD IIa and 25 patients with FCD IIb). We categorized the SOPs into five patterns and evaluated the relationships between the SOPs and the location and pathology of the FCD II subtype.

RESULTS

The most common SOP was no apparent change (39.0%), followed by rhythmic slow wave and repetitive spikes/sharp waves. The SOP of rhythmic slow wave was associated with FCD II in the temporal lobe (P < 0.001), and the SOP of no apparent change was associated with FCD II in the occipital lobe (P = 0.012). The SOPs of rhythmic slow waves and fast activity were most common in FCD IIa, P < 0.001 and 0.031, respectively. The repetitive spikes/sharp waves SOP was the most common pattern in FCD IIb (P < 0.001). The surface SOPs provided correct localization and lateralization of epileptic foci in FCD in 62.1% and 62.7%, respectively. In 61.3% of the patients, over 50% of the SOPs in each patient indicated accurate localization.

CONCLUSIONS

SOPs in surface EEG monitoring are beneficial for presurgical evaluation and lead to localization of epileptic foci and pathologic subtypes of FCD.

Cognitive features of adult focal epilepsy with unknown etiology revealed by the trail making test

PURPOSE

The purpose of this study was to investigate whether the Trail Making Test (TMT) can clarify cognitive dysfunction in focal epilepsy with unknown etiology.

METHODS

Trail Making Test data were obtained from patients with focal epilepsy with no structural abnormalities on magnetic resonance imaging, history or coexistence of central nerve system diseases, intellectual disability, psychiatric disorders, or medications that might interfere with cognitive function. We performed multiple regression analyses with TMT scores as dependent variables and clinical features as independent variables.

RESULTS

We enrolled 125 patients in the study. The statistical analyses revealed that taking fewer antiseizure medications, having a longer duration of education, exhibiting left non-temporal epileptic discharge, and exhibiting right temporal epileptic discharge were associated with shorter time to complete the TMT-A and TMT-B. Older age at the time of last seizure was associated with longer time to complete the TMT-B. In addition, a longer active seizure period was associated with longer time to complete the TMT-A subtracted from time to complete the TMT-B.

CONCLUSIONS

This study indicated that the TMT can be used for assessing the cumulative effects of seizures and the effects of polypharmacy on cognitive function in patients with focal epilepsy. Furthermore, our results indicated that the visuospatial cognitive ability associated with the TMT may depend on the site of epileptic focus of non-lesional focal epilepsy.

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.

Semiology, EEG, and neuroimaging findings in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common type of focal epilepsy. First descriptions of TLE date back in time and detailed portraits of epileptic seizures of temporal origin can be found in early medical reports as well as in the works of various artists and dramatists. Depending on the seizure onset zone, several subtypes of TLE have been identified, each one associated with peculiar ictal semiology. TLE can result from multiple etiological causes, ranging from genetic to lesional ones. While the diagnosis of TLE relies on detailed analysis of clinical as well as electroencephalographic (EEG) features, the lesions responsible for seizure generation can be highlighted by multiple brain imaging modalities or, in selected cases, by genetic investigations. TLE is the most common cause of refractory epilepsy and despite the great advances in diagnostic tools, no lesion is found in around one-third of patients. Surgical treatment is a safe and effective option, requiring presurgical investigations to accurately identify the seizure onset zone (SOZ). In selected cases, presurgical investigations need intracerebral investigations (such as stereoelectroencephalography) or dedicated metabolic imaging techniques (interictal PET and ictal SPECT) to correctly identify the brain structures to be removed.

Hippocampal magnetic resonance imaging in focal onset seizure with impaired awareness—descriptive study from tertiary care centre in southern part of India

Background

Temporal lobe epilepsy is the most common type of focal onset seizure. Focal onset seizure with impaired awareness, previously known as complex partial seizure (CPS), account for 18–40% of all seizure types. Hippocampal sclerosis (HS) is the most common cause of temporal lobe epilepsy, which produces focal onset seizure with impaired awareness. It may be detected in MRI visually, but bilateral abnormalities are better identified using volumetric analysis.

We aimed to compare hippocampal volume in patients with focal onset seizure with impaired awareness visually and quantitatively.

Methodology

This cross-sectional study includes clinically diagnosed cases of 56 focal onset seizure with impaired awareness undergoing MRI at a tertiary teaching hospital in the southern part of India for a duration of 18 months from February 2018 to August 2019.

Results

Out of 53 patients studied using 1.5 T MRI brain with seizure protocols, hippocampal atrophy was identified visually in 13 (24.5%) on the right side, 9 (16.98%) on the left side, and in 6 (11.32%) bilaterally. However, with volumetry, hippocampal atrophy (not taking T2 signal change) was detected in 15 (28.30%) on the right side, 10 (18.86%) on the left side, and in 7 (13.20%) bilaterally. Hippocampal volumes between ipsilateral and contralateral seizure focus were found to have no significant difference (p-0.84).

Conclusions

Though visual analysis is efficient in the diagnosis of pathology, MR volumetry may be used as an expert eye in cases of subtle volume loss.

Seizures induced in electroconvulsive therapy as a human epilepsy model: A comparative case study

OBJECTIVE

Standardized investigation of epileptic seizures and the postictal state may contribute to a better understanding of ictal and postictal phenomena. This comparative case study aims to assess whether electrically induced seizures in electroconvulsive therapy (ECT) show sufficient similarities with spontaneous seizures to serve as a human epilepsy model.

METHODS

We compared six EEG recordings, three ECT-induced seizures and three generalized tonic-clonic seizures, using quantitative electroencephalography (EEG) analyses. EEG recordings during and after ECT sessions (under general anesthesia and muscle paralysis) were collected prospectively, whereas epilepsy data were selected retrospectively. Time-frequency representations, dominant ictal frequencies, and postictal alpha-delta ratios were calculated.

RESULTS

In all EEG recordings, a decrease in dominant ictal frequency was observed, as well as postictal suppression. Postictal alpha-delta ratio indicated the same trend for all: a gradual increase from predominantly delta to alpha frequencies on timescales of hours after the seizure. Postictal spectral representation was similar. Muscle artifacts were absent in ECT-induced seizures and present in spontaneous seizures. Ictal amplitude was higher in epileptic than in ECT-induced seizures. Temporospectral ictal dynamics varied slightly between groups.

SIGNIFICANCE

We show that ictal and postictal characteristics in ECT and patients with generalized tonic-clonic seizures are essentially similar. ECT-induced seizures may be used to investigate aspects of ictal and postictal states in a highly predictable manner and well-controlled environment. This suggests that clinical and electrophysiological observations during ECT may be extrapolated to epilepsy with generalized tonic-clonic seizures.

Cortical low-frequency power correlates with behavioral impairment in animal model of focal limbic seizures

OBJECTIVE

Impairment in consciousness is a debilitating symptom during and after seizures; however, its mechanism remains unclear. Limbic seizures have been shown to spread to arousal circuitry to result in a "network inhibition" phenomenon. However, prior animal model studies did not relate physiological network changes to behavioral responses during or following seizures.

METHODS

Focal onset limbic seizures were induced while rats were performing an operant conditioned behavioral task requiring response to an auditory stimulus to quantify how and when impairment of behavioral response occurs. Correct responses were rewarded with sucrose. Cortical and hippocampal electrophysiology measured by local field potential recordings was analyzed for changes in low- and high-frequency power in relation to behavioral responsiveness during seizures.

RESULTS

As seen in patients with seizures, ictal (p < .0001) and postictal (p = .0015) responsiveness was variably impaired. Analysis of cortical and hippocampal electrophysiology revealed that ictal (p = .002) and postictal (p = .009) frontal cortical low-frequency 3-6-Hz power was associated with poor behavioral performance. In contrast, the hippocampus showed increased power over a wide frequency range during seizures, and suppression postictally, neither of which were related to behavioral impairment.

SIGNIFICANCE

These findings support prior human studies of temporal lobe epilepsy as well as anesthetized animal models suggesting that focal limbic seizures depress consciousness through remote network effects on the cortex, rather than through local hippocampal involvement. By identifying the cortical physiological changes associated with impaired arousal and responsiveness in focal seizures, these results may help guide future therapies to restore ictal and postictal consciousness, improving quality of life for people with epilepsy.

When should we obtain a routine EEG while managing people with epilepsy?

More than eight decades after its discovery, routine electroencephalogram (EEG) remains a safe, noninvasive, inexpensive, bedside test of neurological function. Knowing when a routine EEG should be obtained while managing people with epilepsy is a critical aspect of optimal care. Despite advances in neuroimaging techniques that aid diagnosis of structural lesions in the central nervous system, EEG continues to provide critical diagnostic evidence with implications on treatment. A routine EEG performed after a first unprovoked seizure can support a clinical diagnosis of epilepsy and differentiate those without epilepsy, classify an epilepsy syndrome to impart prognosis, and characterize seizures for antiseizure management. Despite a current viral pandemic, EEG services continue, and the value of routine EEG is unchanged.

Nasopharyngeal electrodes in temporal lobe epilepsy: A reappraisal of their diagnostic utility

OBJECTIVE

To compare electroencephalography (EEG) recordings with nasopharyngeal electrodes (NPEs) plus anterior temporal electrodes (ATEs) (NPE recordings) and those with only ATEs (non-NPE recordings) for the detection of interictal epileptiform discharges (IEDs) in patients with suspected temporal lobe epilepsy (TLE).

METHODS

We retrospectively analyzed the initial EEGs of 229 patients that were recorded simultaneously with ATEs and NPEs in addition to the electrodes of the 10-20 system of electrode placement. Two data sets of NPE and non-NPE recordings were reviewed independently by three interpreters with differing degrees of experience. Discordant findings in the interpretation among the three interpreters were resolved by a consensus to yield final results.

RESULTS

IEDs were detected in 76.4% of patients with NPE recordings compared to 55.5% with non-NPE recordings (p < 0.01). Bilateral independent IEDs were found in 26.2% and 11.4% of EEGs with NPE and non-NPE recordings (p < 0.01). The degree of agreement for the detection of IEDs among the three interpreters was higher with the NPE than with non-NPE recordings (κappa score, 0.70 vs. 0.54). The increased diagnostic yield of NPE recordings for the detection of IEDs was particularly prominent in patients with mesial and non-lesional TLEs.

CONCLUSIONS

EEG recordings using NPEs are useful to improve the sensitivity and level of agreement among interpreters for the detection of IEDs in patients with TLE.

SIGNIFICANCE

NPE recordings may be recommended in routine EEGs for the evaluation of patients with suspected TLE.

Differences in levetiracetam and perampanel treatment-related irritability in patients with epilepsy

PURPOSE

The present study evaluated whether patients with epilepsy who received both levetiracetam (LEV) and perampanel (PER) therapy showed side effects of irritability. The study also examined the relationship between patient characteristics and irritability when it occurred as a side effect.

METHODS

We retrospectively examined medical records of 98 patients with epilepsy who were treated with both LEV and PER at the Department of Psychiatry in the Epilepsy Center of Nishiniigata Chuo National Hospital in Japan. We performed multiple regression analyses with the presence/absence of irritability due to LEV or PER as the dependent variables and clinical characteristics of the patients as independent variables.

RESULTS

LEV and PER caused irritability in 7 and 17 of 98 patients, respectively. LEV- and PER-related irritability did not occur in the same patients. A logistic multiple regression analysis revealed that EEG findings of temporal focal epileptic discharge were significantly associated with increased incidence of irritability due to LEV. LEV-related irritability decreased significantly with higher dosages of LEV. Another logistic multiple regression analysis revealed that a psychiatric comorbidity of irritability and EEG findings of nontemporal focal epileptic discharge were significantly associated with increased incidence of irritability due to PER.

CONCLUSIONS

LEV and PER cause irritability in different patient groups. Additionally, irritability as a side effect was present only at low dosages of LEV, but PER tended to cause irritability even at high dosages.

Initial delta and delayed theta/alpha pattern in the temporal region on ictal EEG suggests purely hippocampal epileptogenicity in patients with mesial temporal lobe epilepsy

OBJECTIVE

To determine whether the ictal scalp EEG findings suggest purely hippocampal epileptogenicity in patients with mesial temporal lobe epilepsy (mTLE) associated with hippocampal sclerosis (HS).

METHODS

Twenty-three patients with mTLE with pathologically confirmed HS were divided into 12 with epileptogenicity only in the hippocampus (HS only group) and 11 with epileptogenicity in both the hippocampus and temporal neocortex or other locations (HS plus group), based on the combination of surgical procedures, postoperative outcome, and pathological findings. Sixteen underwent selective amygdalohippocampectomy (SelAH) and 7 received anterior temporal lobectomy. Ictal scalp EEG findings of 79 focal impaired awareness seizures were compared between the HS only and HS plus groups. We focused on the 1-4 Hz rhythmic delta activity at ictal onset followed by 5-9 Hz rhythmic theta/alpha activity 10-30 s after the onset in the temporal region.

RESULTS

The initial delta and delayed theta/alpha (ID-DT) pattern was observed in 8 of 12 patients in the HS only group, but in none of 11 patients in the HS plus group (p < 0.01).

CONCLUSIONS

ID-DT pattern on ictal EEG suggests purely hippocampal epileptogenicity in mTLE with HS.

SIGNIFICANCE

Patients with the ID-DT pattern are likely to become seizure-free after SelAH.

Algebraic relationship between the structural network's Laplacian and functional network's adjacency matrix is preserved in temporal lobe epilepsy subjects

The relationship between anatomic and resting state functional connectivity of large-scale brain networks is a major focus of current research. In previous work, we introduced a model based on eigen decomposition of the Laplacian which predicts the functional network from the structural network in healthy brains. In this work, we apply the eigen decomposition model to two types of epilepsy; temporal lobe epilepsy associated with mesial temporal sclerosis, and MRI-normal temporal lobe epilepsy. Our findings show that the eigen relationship between function and structure holds for patients with temporal lobe epilepsy as well as normal individuals. These results suggest that the brain under TLE conditions reconfigures and rewires the fine-scale connectivity (a process which the model parameters are putatively sensitive to), in order to achieve the necessary structure-function relationship.

Correlations between interictal extratemporal spikes and clinical features, imaging characteristics, and surgical outcomes in patients with mesial temporal lobe epilepsy

PURPOSE

The significance of interictal epileptiform discharges (IEDs) observed in the extratemporal lobe has not been fully evaluated in patients with mesial temporal lobe epilepsy (MTLE). This study aimed to evaluate the surgical outcomes, clinical features, and functional neuroimaging characteristics of patients in relation to the presence or absence of extratemporal IED in MTLE with hippocampal sclerosis (HS).

METHODS

A total of 165 patients with HS-induced MTLE who had undergone anterior temporal lobectomy were enrolled and stratified into the extratemporal interictal epileptiform discharges (ETD) and the temporal lobe discharges (TD) groups. We analyzed the differentiating features of pre- and postsurgical evaluation data between the two groups. For outcome assessment, only patients with a follow-up of at least 2 years were enrolled, and the outcomes were classified based on Engel classification.

RESULTS

The ETD group showed extensive glucose hypometabolism involving the temporal lobe and extratemporal regions (p < 0.001), and IEDs were observed bilaterally or contralateral to the ictal focus (p = 0.02). However, there was no difference in the surgical outcomes between the two groups. On multivariate analysis, statistically significant variables related to ETD occurrence including seizure onset age were not identified nevertheless.

CONCLUSION

Our results indicate that ETD had a surgical outcome comparable to that of TD. Therefore, a surgical intervention need not be delayed even if extratemporal IED may be found in presurgical long-term scalp EEG monitoring.

Neuroimaging of memory in frontal lobe epilepsy

In a large percentage of epilepsies, seizures have focal onset. These epilepsies are associated with a wide range of behavioral and cognitive deficits sometimes limited to the functions encompassed within the ictal onset zone but, more frequently, expanding beyond it. The presence of impairments associated with neuroanatomical areas outside of the ictal onset zone suggests distal propagation of epileptic activity via brain networks and interconnected whole-brain neural circuitry. In patients with frontal lobe epilepsy (FLE), using functional magnetic resonance imaging (fMRI) to identify deficits in working, semantic, and episodic memory may provide a lens through which to understand typical and atypical network organization. A network approach to focal epilepsy is relevant in these patients because of the frequently noted early age of seizure onset. Early seizure-related disruption in healthy brain development may result in a significant brain reorganization, development of compensation-related mechanisms of dealing with function abnormalities and disruptions, and the propagation of epileptic activity from the focus to widespread brain areas (functional deficit zones). Benefits of a network approach in the study of focal epilepsy are discussed along with considerations for future neuroimaging studies of patients with FLE.

Effective Connectivity Within the Default Mode Network in Left Temporal Lobe Epilepsy: Findings from the Epilepsy Connectome Project

The Epilepsy Connectome Project examines the differences in connectomes between temporal lobe epilepsy (TLE) patients and healthy controls. Using these data, the effective connectivity of the default mode network (DMN) in patients with left TLE compared with healthy controls was investigated using spectral dynamic causal modeling (spDCM) of resting-state functional magnetic resonance imaging data. Group comparisons were made using two parametric empirical Bayes (PEB) models. The first level of each PEB model consisted of each participant's spDCM. Two different second-level models were constructed: the first comparing effective connectivity of the groups directly and the second using the Rey Auditory Verbal Learning Test (RAVLT) delayed free recall index as a covariate at the second level to assess effective connectivity controlling for the poor memory performance of left TLE patients. After an automated search over the nested parameter space and thresholding parameters at 95% posterior probability, both models revealed numerous connections in the DMN, which lead to inhibition of the left hippocampal formation. Left hippocampal formation inhibition may be an inherent result of the left temporal epileptogenic focus as memory differences were controlled for in one model and the same connections remained. An excitatory connection from the posterior cingulate cortex to the medial prefrontal cortex was found to be concomitant with left hippocampal formation inhibition in TLE patients when including RAVLT delayed free recall at the second level.

Using Correlative Properties of Neighboring Pixels to Enhance Contrast-to-Noise Ratio of Abnormal Hippocampus in Patients With Intractable Epilepsy and Mesial Temporal Sclerosis

RATIONALE AND OBJECTIVES

To test whether an image-processing algorithm can aid in visualization of mesial temporal sclerosis on magnetic resonance imaging by selectively increasing contrast-to-noise ratio (CNR) between abnormal hippocampus and normal brain.

MATERIALS AND METHODS

In this Institutional Review Board-approved and Health Insurance Portability and Accountability Act-compliant study, baseline coronal fluid-attenuated inversion recovery images of 18 adults (10 females, eight males; mean age 41.2 years) with proven mesial temporal sclerosis were processed using a custom algorithm to produce corresponding enhanced images. Average (Hmean) and maximum (Hmax) CNR for abnormal hippocampus were calculated relative to normal ipsilateral white matter. CNR values for normal gray matter (GM) were similarly calculated using ipsilateral cingulate gyrus as the internal control. To evaluate effect of image processing on visual conspicuity of hippocampal signal alteration, a neuroradiologist masked to the side of hippocampal abnormality rated signal intensity (SI) of hippocampi on baseline and enhanced images using a five-point scale (definitely abnormal to definitely normal). Differences in Hmean, Hmax, GM, and SI ratings for abnormal hippocampi on baseline and enhanced images were assessed for statistical significance.

RESULTS

Both Hmean and Hmax were significantly higher in enhanced images as compared to baseline images (p < 0.0001 for both). There was no significant difference in the GM between baseline and enhanced images (p = 0.9375). SI ratings showed a more confident identification of abnormality on enhanced images (p = 0.0001).

CONCLUSION

Image-processing resulted in increased CNR of abnormal hippocampus without affecting the CNR of normal gray matter. This selective increase in conspicuity of abnormal hippocampus was associated with more confident identification of hippocampal signal alteration.

[Features of ictal and interictal electrical activity in assessment of the epileptogenic zone in children with focal cortical dysplasias]

Currently, there is no single standard defining what rhythmic activity should be considered as the area of ictal pattern onset. Differences in electroencephalographic patterns associated with different types of focal cortical dysplasias (FCDs) have not been defined. Aim - we aimed to identify features of the ictal onset pattern on a scalp EEG, depending on the histology, location, and extension of epileptogenic zone, as well as to elucidate the relationship between concordance of the interictal and ictal activity localization and ictal onset pattern types.

MATERIAL AND METHODS

We studied scalp video-EEG monitoring data of 38 FCD patients who underwent surgical treatment for intractable epilepsy in the period between 2010 and 2016. We analyzed the data on interictal and ictal activity localization and compared them with the data on FCD types and lesion location.

RESULTS

Two types of the ictal onset pattern on EEG, local and generalized, were identified. The local and generalized types included two and four variants of the ictal onset pattern, respectively. Therefore, 6 combinations of rhythmic activity were identified, which manifested within the first 10 s after the onset of electrographic changes on EEG simultaneously with initial clinical manifestations of seizure. Co-localization of the interictal and ictal activity zones occurred in 42% of cases; of these, 88% of patients had the ictal onset pattern. In the remaining cases (58%), no co-localization of the interictal and ictal activity zones was detected; of these, 76% of patients were assigned to the group with the generalized ictal onset pattern. The local ictal onset pattern was more common in patients with type II FCD, while the generalized ictal onset pattern was more common in patients with type I and type III FCD. No correlation between the ictal onset pattern type and the lesion localization was found.

CONCLUSION

We describe two ictal onset pattern types, local and generalized, on EEG in children with FCD. The co-localization of ictal and interictal activity zones prevails in the local ictal onset pattern group. The local ictal onset pattern is often associated with type II FCD. In the case of type I and type III FCD, the generalized ictal onset pattern predominates. There is no clear relationship between the ictal onset pattern type and the lesion location.

Focal epilepsies and focal disorders

Electroencephalographic (EEG) investigations are crucial in the diagnosis and management of patients with focal epilepsies. EEG may reveal different interictal epileptiform discharges (IEDs: abnormal spikes, sharp waves). The EEG visibility of a spike depends on the surface area of cortex involved (>10cm²) and the brain localization of cortical generators. Regions generating IEDs (defining the "irritative zone") are not necessarily equivalent to the seizure onset zone. Focal seizures are dynamic processes originating from one or several brain regions (that generate fast oscillations and are called the epileptogenic zone) before spreading to other structures (that generate lower frequency oscillations and are called the propagation zone). Several factors limit the expression of seizures on scalp EEG, such as the area involved, degree of synchronization, and depth of the cortical generators. Different scalp EEG seizure onset patterns may be observed: fast discharge, background flattening, rhythmic spikes, sinusoidal discharge, or sharp activity. However, to a large extent EEG changes are linked to seizure propagation. Finally, in the context of presurgical evaluation, the combination of interictal and ictal EEG features is crucial to provide an optimal hypothesis concerning the epileptogenic zone.

Chemogenetic silencing of hippocampal neurons suppresses epileptic neural circuits

We investigated how pathological changes in newborn hippocampal dentate granule cells (DGCs) lead to epilepsy. Using a rabies virus-mediated retrograde tracing system and a designer receptors exclusively activated by designer drugs (DREADD) chemogenetic method, we demonstrated that newborn hippocampal DGCs are required for the formation of epileptic neural circuits and the induction of spontaneous recurrent seizures (SRS). A rabies virus-mediated mapping study revealed that aberrant circuit integration of hippocampal newborn DGCs formed excessive de novo excitatory connections as well as recurrent excitatory loops, allowing the hippocampus to produce, amplify, and propagate excessive recurrent excitatory signals. In epileptic mice, DREADD-mediated-specific suppression of hippocampal newborn DGCs dramatically reduced epileptic spikes and SRS in an inducible and reversible manner. Conversely, specific activation of hippocampal newborn DGCs increased both epileptic spikes and SRS. Our study reveals an essential role for hippocampal newborn DGCs in the formation and function of epileptic neural circuits, providing critical insights into DGCs as a potential therapeutic target for treating epilepsy.

Lateralization Value of Low Frequency Band Beamformer Magnetoencephalography Source Imaging in Temporal Lobe Epilepsy

Objective: In presurgical evaluation of temporal lobe epilepsy (TLE), selection of the resection side is challenging when bilateral temporal epileptiform discharges or structural abnormalities are present. We aim to evaluate the lateralization value of beamformer analysis of magnetoencephalography (MEG) in TLE. Methods: MEG data from 14 TLE patients were analyzed through beamformer analysis. We measured the hemispherical power distribution of beamformer sources and calculated the lateralization index (LI). We calculated the LI at multiple frequencies to explore the frequency dependency and at the delta frequency to define laterality. LI values ranging from -1 to -0.05 indicated right hemispheric dominance. LI values ranging from 0.05 to 1 indicated left hemispheric dominance. LI values ranging from -0.05 to 0.05 defined bilaterality. We measured the power of beamformer sources with a 9-s duration to explore time dependency. Results: The beamformer analysis showed that 10/14 patients had power dominance ipsilateral to resection. The delta frequency band had a higher lateralization value than other frequency bands. A time-dependent power fluctuation was found in the delta frequency band. Conclusions: MEG beamformer analysis, especially in the delta band, might efficiently provide additional information regarding lateralization in TLE.

Unusual ictal propagation patterns suggesting poor prognosis after temporal lobe epilepsy surgery: Switch of lateralization and bilateral asynchrony

OBJECTIVE

The objective of this study was to investigate unusual ictal propagation patterns in patients with drug-resistant temporal lobe epilepsy (TLE) and reveal their electrophysiological, neuroimaging, and prognostic properties after surgery.

METHODS

Among 248 patients with TLE who underwent scalp video-electroencephalographic (EEG) monitoring, 24 patients with 'switch of lateralization' or 'bilateral asynchrony' in at least one of their seizures (9.3%) were analyzed retrospectively. The postoperative outcome was determined in 16 patients who had undergone epilepsy surgery.

RESULTS

All but 5 of the included patients had hippocampal sclerosis (HS) as their magnetic resonance imaging (MRI) findings. Twelve out of 16 patients (75%) who had surgery were seizure-free for at least 1 year. Nine out of 12 patients (75%) with good outcome had unilateral interictal EEG discharges in temporal regions whereas 3 out of 4 patients with poor outcome had bilateral temporal interictal spiking (p = 0.018).

CONCLUSION

Unusual ictal propagation patterns are not always related to poor prognosis after surgery in patients with TLE. Patients with unilateral interictal spiking in the temporal region tend to have good outcome despite these unusual patterns. These patterns can also be seen in patients with TLE with other etiologies besides the well-known HS in MRI.

Correlation of Electroencephalography and Magnetic Resonance Imaging in Patients with Mesial Temporal Sclerosis

Introduction

To determine the lateralization of lesion by non-invasive methods through correlation of cranial magnetic resonance imaging (MRI) and electroencephalography (EEG) findings in patients with mesial temporal sclerosis (MTS).

Methods

This study included 40 patients (Age range, 19 to 55 years) among 1850 patients who were attending outpatient epilepsy clinic of Haydarpaşa Numune Hospital between the years 2000 and 2013. Exclusion criteria were surgery due to MTS, metabolic and systemic disorders, indefinite diagnosis, and inadequate MRI and EEG evaluations.

Results

EEG findings were within normal limits in 10 (25%) patients who had MTS on MRI. Of these, 5 patients had right MTS, 4 had left MTS, and one patient had bilateral MTS.

Conclusion

In this study, we used electrophysiological diagnostic methods together with MR imaging to determine epileptogenic localization in patients with MTS. We suggest that, when correlated with MRI, EEG is a non-invasive and easy method to identify lateralization findings.

Impact of injection time on migration of SPECT seizure onset in temporal lobe epilepsy

In this work, we investigated an impact of injection time on migration of seizure-onset in ictal/interictal single photon emission computed tomography (SPECT) study for patients with temporal lobe epilepsy. We selected 33 patients with refractory temporal lobe epilepsy who underwent ictal/interictal SPECT studies and had preoperative intracranial EEG result or surgical resection which was used as reference for seizure location. We divided all patients into two groups, which are the fast and the delayed groups; the delayed group comprised patients with injection time more than a cutoff time and vice versa. Using the subtraction ictal-interictal SPECT co-registered with SPECT (SISCOS) with varied Z-threshold (1.0, 1.5, 2.0 and 2.5), a method similar to subtraction ictal SPECT co-registered to magnetic resonance imaging (MRI) (SISCOM), a seizure-onset region in the SISCOS image was localized at the region with maximum sum of Z-scores. For each pair of cutoff time and Z-threshold, we determined the migratory proportion which was defined as the proportion of patients whose seizure-onset location based on SISCOS image was discordant with the reference. At cutoff time of 32-35 seconds and the Z-threshold of 2.0, the migratory proportion values were 7/26 (26.9%) and 5/7 (71.4%) in the fast and the delayed groups, respectively. At the same range of cutoff time with the Z-threshold of 2.5, the migratory proportion was 8/26 (30.8%) in the fast group while the proportion was 5/7 (71.4%) in the delayed group. Using Fisher's exact test, the migratory proportion values at the Z-threshold of 2.0 and 2.5 were significantly different between the fast and the delayed groups (p = 0.0709 and 0.0838, respectively), suggesting that patients with temporal lobe epilepsy who undergo an ictal/interictal SPECT study with injection time longer than 35 seconds tend to have seizure-onset zone migration in the SISCOS analysis with the traditionally-used Z-threshold of 2.0.

Working memory deficit in drug-resistant epilepsy with an amygdala lesion

This study compared temporal lobe epilepsy (TLE) patients with amygdala lesion (AL) without hippocampal sclerosis (HS) (TLE-AL) with patients with TLE and HS without AL (TLE-HS). Both subtypes of TLE arose from the right hemisphere.

The TLE-AL group exhibited a lower Working Memory Index (WMI) on the Wechsler Adult Intelligence Scale, third edition (WAIS-III), indicating that the amygdala in the right hemisphere is involved in memory-related function. [18F]fluorodeoxyglucose positron emission topography (FDG-PET) showed glucose hypometabolism limited to the right uncus for the TLE-AL group.

The results suggest the importance of considering cognitive functions in the non-dominant hemisphere to prevent impairment after surgery.

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Low working memory index (WMI) was found due to a right amygdala lesion (AL).

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Glucose hypometabolism was limited to the right uncus for the Temporal Lobe Epilepsy-AL (TLE-AL) patients

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Glucose hypometabolism was associated with low WMI in the TLE-AL patients

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We suggest the need to consider cognitive function in non-dominant hemisphere

Widespread abnormalities in white matter integrity and their relationship with duration of illness in temporal lobe epilepsy

Objective

Elucidation of abnormal connections throughout the whole brain is necessary to understand temporal lobe epilepsy (TLE). We examined abnormalities in whole‐brain white matter integrity and their relationship with duration of illness in patients with TLE.

Methods

The subjects were 15 patients with TLE and 17 healthy controls. Mean duration of illness in the TLE group was 21.6 years. Tract‐based spatial statistics (TBSS) were used for diffusion tensor imaging (DTI) analysis. Four diffusion tensor metrics, that is, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated and then examined for differences between the TLE and healthy control groups. We also examined for correlations between DTI parameters and duration of illness in the TLE group.

Results

In the TLE group, compared with the healthy control group, FA was reduced, and MD and RD were increased, not only in the limbic and temporal lobe regions and their directly connecting regions in both hemispheres, but also in remote white matter regions. Duration of illness showed a significant negative correlation with mean whole‐brain FA and a significant positive correlation with both mean whole‐brain MD and RD. Brain regions showing correlation between disease duration and DTI metrics also extended to the limbic area and its connecting regions, and to remote white matter regions.

Significance

The results of this study suggest that widespread abnormalities in white matter integrity in patients with TLE are associated with long‐term disease.

Predictors of outcome of surgery in adults with mesial lesional temporal lobe epilepsy

Background We report the clinical characteristics and outcome of epilepsy surgery in adult patients with intractable epilepsy due to isolated lesional temporal lobe epilepsy (TLE).

Methods Retrospective analysis of clinical and outcome characteristics in 47 consecutive adult patients with intractable epilepsy due to isolated lesional TLE who underwent epilepsy surgery from November 2009 to January 2015 was done to predictors of outcome.

Results The mean age at surgery of the study population was 30.74 ± 10.85 years with 20 (43.5%) women. While the average age at onset of epilepsy was 20.12 ± 12.52 years, average duration of epilepsy was 10.78 ± 7.96 years. Favourable Engels outcome was observed in 39 (84.8%) of the patients. Findings on histopathology reported glioma in 24 (52.0%) of the patients. On comparing patients with favourable outcome (n = 39) with those with unfavourable outcome (n = 7), age at surgery was significantly higher in patients with unfavourable outcome (40.14 ± 11.69 years vs 29.05 ± 9.92 years; p = 0.011). Higher percentage of patients with unfavourable outcome scored poor on pre-surgical IQ tests (42.9% vs 7.7%; p = 0.037). On further analysis for predictors of outcome, age at surgery (β = 0.858; 95% CI 0.738–0.997) significantly predicts outcome (β = 1.166; 95% CI 0.931–1.461; p = 0.182), whereas pre-surgical poor IQ showed a trend towards being associated with unfavourable outcome (β = 0.079; 95% CI 0.005–1.287; p = 0.075).

Conclusion Surgery for intractable epilepsy due to isolated lesional TLE has favourable outcome in vast majority (84.8%) of carefully selected patients. Age at surgery predicts outcome in these patients.

Tantrums, Emotion Reactions and Their EEG Correlates in Childhood Benign Rolandic Epilepsy vs. Complex Partial Seizures: Exploratory Observations

We explored associations between EEG pathophysiology and emotional/behavioral (E/B) problems of children with two types of epilepsy using standard parent questionnaires and two new indicators: tantrums recorded by parents at home and brief, emotion-eliciting situations in the laboratory. Children with Benign Rolandic epilepsy (BRE, N = 6) reportedly had shorter, more angry tantrums from which they recovered quickly. Children with Complex Partial Seizures (CPS, N = 13) had longer, sadder tantrums often followed by bad moods. More generally, BRE correlated with anger and aggression; CPS with sadness and withdrawal. Scores of a composite group of siblings (N = 11) were generally intermediate between the BRE and CPS groups. Across all children, high voltage theta and/or interictal epileptiform discharges (IEDs) correlated with negative emotional reactions. Such EEG abnormalities in left hemisphere correlated with greater social fear, right hemisphere EEG abnormalities with greater anger. Right hemisphere localization in CPS was also associated with parent-reported problems at home. If epilepsy alters neural circuitry thereby increasing negative emotions, additional assessment of anti-epileptic drug treatment of epilepsy-related E/B problems would be warranted.

Three phase-ictal scalp EEG patterns in patients with seizures arising from the cortex facing the interhemispheric fissure

OBJECTIVE

Ictal scalp EEG patterns have been reported to vary across onset regions. We assessed the sequential EEG changes during seizure events on scalp EEG, and tested our hypothesis that patients with focal seizures arising from the cortex facing the interhemispheric fissure (IHF cortex) would be specifically characterized by 3 phase-EEG patterns (3Ph-EEG).

METHODS

Patient inclusion criteria were: 1) focal epilepsy and 2) ictal onset records on scalp and intracranial video-EEG. Patients were classified into one of the three groups: the IHF group, mesial temporal (MT) group, or lateral convexity (LC) group, based on the localization of the ictal onset zone (IOZ) on intracranial video-EEG. We defined 3Ph-EEG on ictal scalp EEG as follows: phase 1, brief spike/fast wave burst; phase 2, diffuse attenuation; and phase 3, focal rhythmic activity with evolution. We determined if the occurrence ratios of 3Ph-EEG and each of the three phases differed between the groups (IHF and others).

RESULTS

We studied 36 patients aged 8-59 years (mean, 30 years). Ten patients were classified as IHF, 16 as MT, and 10 as LC group from 303 ictal events on intracranial EEG. 193 seizures on scalp EEG consisted of 79 seizures in IHF; 58 in MT; 56 in LC group. Sixty-nine seizures (92%) in nine patients (90%) in IHF group showed 3Ph-EEG, whereas none of the seizures in MT and LC groups showed the 3Ph-EEG. Multivariate logistic regression analysis suggested that the presence of 3Ph-EEG (p < 0.01) and phase 2 (p = 0.03) components were predictive of IHF scalp EEG onset.

SIGNIFICANCE

The 3Ph-EEG may be observed preferentially in patients with focal seizures from IHF cortex. Observation of the ictal phases on scalp EEG may warrant consideration of intracranial EEG sampling for the presurgical evaluation.

Microbeam radiation therapy - grid therapy and beyond: a clinical perspective

Microbeam irradiation is spatially fractionated radiation on a micrometer scale. Microbeam irradiation with therapeutic intent has become known as microbeam radiation therapy (MRT). The basic concept of MRT was developed in the 1980s, but it has not yet been tested in any human clinical trial, even though there is now a large number of animal studies demonstrating its marked therapeutic potential with an exceptional normal tissue sparing effect. Furthermore, MRT is conceptually similar to macroscopic grid based radiation therapy which has been used in clinical practice for decades. In this review, the potential clinical applications of MRT are analysed for both malignant and non-malignant diseases.

Hippocampal Expression of Connexin36 and Connexin43 during Epileptogenesis in Pilocarpine Model of Epilepsy

BACKGROUND

Gap junctions (GJs) provide direct intercellular communications that are formed by hexameric protein subunits, called connexin (Cx). The role of Cxs in epileptogenesis has not received sufficient attention. Hippocampus with critical function in epileptogenesis has a wide network of GJs. We examined the protein expression levels of hippocampal Cx36 (the prominent Cx present between GABAergic interneurons) and Cx43 (the main Cx expressed by astrocytes) during epileptogenesis in the pilocarpine model of epilepsy.

METHODS

Male Wistar rats received scopolamine (1 mg/kg, s.c.). Pilocarpine (380 mg/kg, i.p.) was administered 30 min thereafter to induce status epilepticus (SE). SE was stopped 2 h later by diazepam (10 mg/kg, i.p.). Cx36 and Cx43 protein expression was assessed by Western blot analysis in the hippocampus of SE-experienced rats, after injection of diazepam (F0 subgroup), after acquisition of focal seizures (F3 subgroup), and after development of generalized seizures (F5 subgroup). The control subgroups, C0, C3, and C5, were aged-matched rats, which received saline (1 ml/kg, i.p.) instead of pilocarpine. Injection of scopolamine and diazepam, and dissection of hippocampi were carried out at the same time interval as the test subgroups.

RESULTS

SE emerged in 67.1% of pilocarpine-treated animals. Focal and generalized seizures developed 3.8±0.4 and 7.0±0.5 days after SE, respectively. Cx36 protein abundance was not significantly different between test and control groups in the three time points. However, Cx43 protein level showed 40% increase in F3 subgroup (P<0.05 compared to C3, P<0.01 compared to F0 and F5).

CONCLUSION

Hippocampal Cx43 is overexpressed in pilocarpine model of epileptogenesis after acquisition of focal seizures.

Mitophagy in Refractory Temporal Lobe Epilepsy Patients with Hippocampal Sclerosis

This study aimed to determine if there is an association between mitophagy and refractory temporal lobe epilepsy (rTLE) with hippocampal sclerosis. During epilepsy surgery, we collected tissue samples from the hippocampi and temporal lobe cortexes of rTLE patients with hippocampal sclerosis (as diagnosed by a pathologist). Transmission electron microscopy (TEM) was used to study the ultrastructural features of the tissue. To probe for mitophagy, we used fluorescent immunolabeling to determine if mitochondrial and autophagosomal markers colocalized. Fourteen samples were examined. TEM results showed that early autophagosomes were present and mitochondria were impaired to different degrees in hippocampi. Immunofluorescent labeling showed colocalization of the autophagosome marker LC3B with the mitochondrial marker TOMM20 in hippocampi and temporal lobe cortexes, indicating the presence of mitophagy. Mitochondrial and autophagosomal marker colocalization was lower in hippocampus than in temporal lobe cortex (P < 0.001). Accumulation of autophagosomes and mitophagy activation are implicated in rTLE with hippocampal sclerosis. Aberrant accumulation of damaged mitochondria, especially in the hippocampus, can be attributed to defects in mitophagy, which may participate in epileptogenesis.