Interictal EEG Discharges Research Articles

Relationship Between Electroencephalography and Seizure Outcome in Typical Absence Seizures in Children

BackgroundTypical absence seizures (TAS) are seen in idiopathic generalized epilepsy. Electroencephalography (EEG) contributes to syndrome characterization and counseling in an area where genetics does not currently play a significant role. Prominent interictal EEG findings are seen in juvenile absence epilepsy (JAE) and are thus thought to be associated with less favorable outcome in any TAS case despite lack of evidence. Our study evaluates EEG findings and their association with seizure outcomes in children with TAS. MethodsRetrospective cohort study of 123 children over 10 years with extensive EEG analysis and medical record review. Phone interviews ascertained longer-term outcomes. EEG reviewers were unaware of outcomes. ResultsTotal cohort included 123 children with phone review completed in 98. Median follow-up was 5 years 9 months. Seizure freedom was seen in 59% off antiseizure medicines (ASMs). Interictal findings included focal discharges in 29%, fragments of spike-wave (SW) discharges in 82.1%, and generalized interictal discharges in 63.4%. Interictal SW was more likely in those who slept (100%, 18 of 18) versus those who did not (57%, 60 of 105) (P < 0.001). Outcome analysis found no associations between focal or generalized interictal findings and seizure freedom, relapse off ASM, occurrence of other seizure types, or response to first ASM. ConclusionFocal and generalized interictal EEG discharges are common in children with TAS and are not associated with poorer outcomes. These interictal findings were traditionally associated with JAE rather than childhood absence epilepsy and were thus believed to be associated with potentially poorer outcome, which is probably not the case.

From theory to practical fundamentals of electroencephalographic source imaging in localizing the epileptogenic zone.

With continued advancement in computational technologies, the analysis of electroencephalography (EEG) has shifted from pure visual analysis to a noninvasive computational technique called EEG source imaging (ESI), which involves mathematical modeling of dipolar and distributed sources of a given scalp EEG pattern. ESI is a noninvasive phase I test for presurgical localization of the seizure onset zone in focal epilepsy. It is a relatively inexpensive modality, as it leverages scalp EEG and magnetic resonance imaging (MRI) data already collected typically during presurgical evaluation. With an adequate number of electrodes and combined with patient-specific MRI-based head models, ESI has proven to be a valuable and accurate clinical diagnostic tool for localizing the epileptogenic zone. Despite its advantages, however, ESI is routinely used at only a minority of epilepsy centers. This paper reviews the current evidence and practical fundamentals for using ESI of interictal and ictal epileptic activity during the presurgical evaluation of drug-resistant patients. We identify common errors in processing and interpreting ESI studies, describe the differences in approach needed for localizing interictal and ictal EEG discharges through practical examples, and describe best practices for optimizing the diagnostic information available from these studies.

Phenotype of heterozygous variants of dehydrodolichol diphosphate synthase

To further identify and broaden the phenotypic characteristics and genotype spectrum of the dehydrodolichol diphosphate synthase (DHDDS) gene. Pathogenic variants of DHDDS were identified by whole-exome sequencing; clinical data of 10 patients (six males, four females; age range 2-14y; mean age 5y 9mo, SD 3y 3mo) were collected and analysed. All patients had seizures, and myoclonic seizures could be seen in eight patients, with myoclonic status epilepticus in three. The interictal electroencephalogram (EEG) in four patients at seizure onset showed generalized slow waves, slow wave mixed spikes, and spike and waves. Tremor, ataxia, and hypertonia was observed in six, five, and three patients respectively. The results of short-latency somatosensory evoked potential in two patients were normal, and the symptom of tremor was captured on EEG without time-locked discharges in one patient, suggesting that the tremor in both patients was a motor impairment rather than myoclonic seizures. Global developmental delay occurred in all patients, among whom nine showed severe intellectual disability and one moderate. Five DHDDS variants were identified, three of which have not been reported previously. Myoclonic seizure is the most common seizure type in heterozygous DHDDS variants, while myoclonic status epilepticus can also occur. The pattern of interictal EEG discharges is characterized by slow waves rather than spike and waves, and generalized discharges was prominent.

Optimized set of criteria for defining interictal epileptiform EEG discharges

ObjectiveTo find and validate the optimal combination of criteria that define interictal epileptiform EEG discharges (IEDs). Our target was a specificity over 95%, to avoid over-reading in clinical EEG. MethodsWe constructed 63 combinations of the six criteria from the operational definition of IEDs, recently issued in the EEG-glossary of the International Federation of Clinical Neurophysiology (IFCN). The diagnostic gold standard was derived from video-EEG recordings. In a testing EEG dataset from 100 patients, we selected the best performing combinations of criteria and then we validated them in an independent dataset from 70 patients. We compared their performance with subjective, expert-scorings and we determined inter-rater agreement (IRA). ResultsWithout using criteria, the specificity of expert-scorings was lower than the pre-defined threshold (86%). The best performing combination of criteria was the following: waves with spiky morphology, followed by a slow-afterwave and voltage map suggesting a source in the brain. In the validation dataset this achieved a specificity of 97% and a sensitivity of 89%. IRA was substantial. ConclusionsThe optimized set of criteria for defining IEDs has high accuracy and IRA. SignificanceUsing these criteria will contribute to decreasing over-reading of EEG and avoid misdiagnosis of epilepsy.

Respective Contribution of Ictal and Inter-ictal Electrical Source Imaging to Epileptogenic Zone Localization.

Interictal electrical source imaging (ESI) encompasses a risk of false localization due to complex relationships between irritative and epileptogenic networks. This study aimed to compare the localizing value of ESI derived from ictal and inter-ictal EEG discharges and to evaluate the localizing value of ESI according to three different subgroups: MRI lesion, presumed etiology and morphology of ictal EEG pattern. We prospectively analyzed 54 of 78 enrolled patients undergoing pre-surgical investigation for refractory epilepsy. Ictal and inter-ictal ESI results were interpreted blinded to- and subsequently compared with stereoelectroencephalography as a reference method. Anatomical concordance was assessed at a sub-lobar level. Sensitivity and specificity of ictal, inter-ictal and ictal plus inter-ictal ESI were calculated and compared according to the different subgroups. Inter-ictal and ictal ESI sensitivity (84% and 75% respectively) and specificity (38% and 50% respectively) were not statistically different. Regarding the sensitivity, ictal ESI was never higher than inter-ictal ESI. Regarding the specificity, ictal ESI was higher than inter-ictal ESI in malformations of cortical development (MCD) (60% vs. 43%) and in MRI positive patients (49% vs. 30%). Within the ictal ESI analysis, we showed a higher specificity for ictal spikes (59%) and rhythmic discharges > 13Hz (50%) than rhythmic discharges < 13Hz (37%) and (ii) for MCD (60%) than in other etiologies (29%). This prospective study demonstrates the relevance of a combined interpretation of distinct inter-ictal and ictal analysis. Inter-ictal analysis gave the highest sensitivity. Ictal analysis gave the highest specificity especially in patients with MCD or a lesion on MRI.

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

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. 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. 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). 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.

Benign epilepsy with centrotemporal spikes: Correlating spike frequency and neuropsychology.

Neuropsychological sequelae are a feature of benign epilepsy with centrotemporal spikes (BECTS) in children. A correlation between the frequency of interictal EEG discharges and the cognitive as well as behavioral profile of the patients has been suspected but not proven. Children with BECTS that had not yet been treated were included into a randomized controlled trial. In the initial visit, EEGs were recorded. The frequency of interictal discharges was quantified. Correlations between the discharge frequency and the performance in a neuropsychological test battery were examined. The cognitive test results were within or slightly above normal range (Culture-free intelligence test: 99.4%-confidence interval [CI]: [50.3, 59.9], test standardized to a population mean of 50). Parent-reported behavioral abnormalities were statistically significantly increased (CBCL total score CI: [51.9, 61.9], population mean as above). Correlations between the frequency of interictal epileptic discharges and the test results could not be identified (lowest encountered P-value: 0.034, not significant after correction for multiple testing). The data do not support the hypothesis that the frequency of the interictal EEG discharges influences the neurocognitive performance or behavioral parameters of children with BECTS.

Clinical Features at the Time of Diagnosis of Benign Epilepsy With Centrotemporal Spikes Do Not Predict Subsequent Seizures

BackgroundBenign epilepsy with centrotemporal spikes (BECTs) usually follows a self-limited course, with a single or few seizures. Assessing the likelihood of a second seizure after the first event may help establishing the need for antiepileptic drug therapy at the time of diagnosis. We aimed at identifying clinical and/or electrographic features that could predict the occurrence of a second seizure. MethodsWe reviewed the clinical and electroencephalographic (EEG) data of children diagnosed with BECTs between 2006 and 2012. Demographic, clinical, routine, and sleep-deprived EEG findings were analyzed. FindingsSeventy-three patients were reviewed who had been followed for four to 10 years. Age at first seizure ranged between three and 16 years (median nine years). In 28 children the first seizure occurred after 10 years age. Ten children were aged three to six years. EEG data were available for 64 individuals. No specific clinical features or seizure semiology were predictive of a second seizure. Neither the type nor the location of interictal EEG discharges was indicative of a second seizure. Among children whose EEG records depicted sleep-related enhancement of interictal discharges, 58.8% sustained a second seizure. This finding did not reach statistical significance. Forty children sustained a second seizure, mostly within 12 months in 30 (P < 0.0001). Among these 30 children, the second event occurred after a median period of 156 days, compared with 654 days for cases with a second seizure after 12 months. ConclusionsNeither clinical features, seizure characteristics, nor routine EEG findings were effective in predicting the likelihood of a second seizure in children with BECTs.

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

ObjectiveThe 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. MethodsAmong 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. ResultsAll 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). ConclusionUnusual 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.

Effect of interictal epileptiform EEG discharges on cognitive functions in epileptic children

Background: Epilepsy is a chronic disorder of the brain that affects people of all ages Neuropsychological impairment is an important comorbidity of chronic epilepsy in the majority of children with epilepsy. interictal epileptiform EEG discharges may present as a complicating factor in spite of being seizure free. In a group of children with interictal EEG discharges there is sudden and unexpected decline of school performance as the first symptom of epilepsy. Consequently, accumulating cognitive impairment, and even a decline in IQ scores, is reported in epileptic children with frequent episodes with epileptiform EEG discharges. Aim of the Work: To evaluate the possible relationship between interictal EEG discharge and cognitive function in a sample of Egyptian epileptic children. Patients and Methods: The ethical approval was obtained from the Hospital Ethical Research Committee. Each patient and/or parents entering the study signed an informed consent. This study was conducted on 140 children selected from Epilepsy Outpatient Clinic of Al-Azhar University Hospitals during a period of two years starting from June 2016 untill June 2018. A specialized pediatric neurology sheet was taken. EEG and cognitive assessment of epileptic patients with and without epileptiform EEG discharges using Stanford-Binet intelligence scale and P300 by ERP were performed to each patient two times 3 months in between. Results: we found that patients with frequent IEDs had high mean P300 latency and low IQ when compared to patients with infrequent and normal EEG examination. In addition, the mean p300 latency significantly reduced with rising in IQ (more improvement in cognitive function) after disappearance of IED in some patients. Conclusion: Interictal epileptiform EEG discharge had an additional effect on cognitive function especially if generalized and of high frequency. This effect might be often underestimated and might accumulate, and have a severe cognitive impact. So, treatment of epileptic patients should put in concern reduction or even treatment of IEDs as controlling of these IED lead to improvement of cognition.

Effect of interictal epileptiform EEG discharges on cognitive functions in epileptic children

Background: Epilepsy is a chronic disorder of the brain that affects people of all ages Neuropsychological impairment is an important comorbidity of chronic epilepsy in the majority of children with epilepsy. interictal epileptiform EEG discharges may present as a complicating factor in spite of being seizure free. In a group of children with interictal EEG discharges there is sudden and unexpected decline of school performance as the first symptom of epilepsy. Consequently, accumulating cognitive impairment, and even a decline in IQ scores, is reported in epileptic children with frequent episodes with epileptiform EEG discharges. Aim of the Work: To evaluate the possible relationship between interictal EEG discharge and cognitive function in a sample of Egyptian epileptic children. Patients and Methods: The ethical approval was obtained from the Hospital Ethical Research Committee. Each patient and/or parents entering the study signed an informed consent. This study was conducted on 140 children selected from Epilepsy Outpatient Clinic of Al-Azhar University Hospitals during a period of two years starting from June 2016 untill June 2018. A specialized pediatric neurology sheet was taken. EEG and cognitive assessment of epileptic patients with and without epileptiform EEG discharges using Stanford-Binet intelligence scale and P300 by ERP were performed to each patient two times 3 months in between. Results: we found that patients with frequent IEDs had high mean P300 latency and low IQ when compared to patients with infrequent and normal EEG examination. In addition, the mean p300 latency significantly reduced with rising in IQ (more improvement in cognitive function) after disappearance of IED in some patients. Conclusion: Interictal epileptiform EEG discharge had an additional effect on cognitive function especially if generalized and of high frequency. This effect might be often underestimated and might accumulate, and have a severe cognitive impact. So, treatment of epileptic patients should put in concern reduction or even treatment of IEDs as controlling of these IED lead to improvement of cognition.

Why Are Children With Epileptic Encephalopathies Encephalopathic?

The epileptic encephalopathies are devastating conditions characterized by frequent seizures, severely abnormal electroencephalograms (EEGs), and cognitive slowing or regression. The cognitive impairment in the epileptic encephalopathies may be more concerning to the patient and parents than the epilepsy itself. There is increasing recognition that the cognitive comorbidity can be both chronic, primarily due to the underlying etiology of the epilepsy, and dynamic or evolving because of recurrent seizures, interictal spikes, and antiepileptic drugs. Much of scholars' understanding of the neurophysiological underpinnings of cognitive dysfunction in the epileptic encephalopathies comes from rodent studies. Frequent seizures and interictal EEG discharges in rats lead to considerable spatial and social-cognitive deficits. Paralleling these cognitive deficits are dyscoordination of dynamic neural activity within and between the neural networks that subserve normal cognitive processes.

Strong “intrinsic” functional connectivity of epileptic networks independent of scalp interictal epileptiform EEG discharges

Objective Epileptic activity arises from dysfunction of pathological neuronal network (epileptic network). Aim: to assess maintenance of epileptic network in between IEDs occurrence. Methods We acquired simultaneous EEG-fMRI resting state in 10 drug-resistant focal epilepsy patients, having multifocal BOLD response and maximal t -value in the IED field. We compared results of functional connectivity (FC) before and after removing IEDs effect for two seed types: a 10mm-diameter sphere drawn in the BOLD map maximum and the epileptic component obtained by Indipendent component analysis. We evaluated the results in terms of mean t -value and the percentage of overlap between the FC maps. Results Mean t -value was significant lower after regressing out the IEDs at group level ( p = 0.008 for sphere; p = 0.0004 for epileptic component). Overlap extent was 85% ± 12% and 87% ± 12% for the sphere and the epileptic component, respectively. Conclusions Regions involved in a specific epileptic network show coherent oscillation independent of the occurrence of interictal activity. This could indicate the presence of epileptic activity invisible to the scalp-EEG or the presence of new and pathological resting state networks. Key message Regions involved in a specific epileptic network show functional coupling independently of the occurrence of interictal activity as revealed on scalp EEG.

Mozart's music in children with drug-refractory epileptic encephalopathies

Mozart's sonata for two pianos in D major, K448, has been shown to decrease interictal EEG discharges and recurrence of clinical seizures in both adults and young patients. In this prospective, open-label study, we evaluated the effect of listening to a set of Mozart's compositions, according to the Tomatis method, on sleep quality and behavioral disorders, including auto-/hetero-aggression, irritability, and hyperactivity, in a group of children and adolescents with drug-resistant epilepsy. The study group was composed of 11 outpatients (7 males and 4 females), between 1.5years and 21years of age (mean age: 11.9years), all suffering from drug-resistant epileptic encephalopathy (n=11). All of them had a severe/profound intellectual disability associated with cerebral palsy. During the study period, each patient had to listen to a set of Mozart's compositions 2h per day for fifteen days for a total of 30h, which could be distributed over the day depending on the habits and compliance of each patient. The music was filtered by a device preferably delivering higher sound frequencies (>3000Hz) according to the Tomatis principles. The antiepileptic drug therapy remained unchanged throughout the study period. During the 15-day music therapy, 2 out of 11 patients had a reduction of 50-75% in seizure recurrence, and 3 out of 12 patients had a reduction of 75-89%. Overall, 5 (45.4%) out of 11 patients had a ≥50% reduction in the total number of seizures, while the percentage decrease of the total seizure number (11/11) compared with baseline was -51.5% during the 15-day music therapy and -20.7% in the two weeks after the end of treatment. All responders also had an improvement in nighttime sleep and daytime behavior.

Spotlight on the May 19 Issue

#### Notable in Neurology This issue features an article on a novel epilepsy endpoint, time to prerandomization monthly seizure count, and whether it could differentiate efficacious from nonefficacious therapy in perampanel trials. Another article investigated increased oxidative stress in the motor cortex and its relation to disease severity in amyotrophic lateral sclerosis. Another featured article focuses on a novel AARS mutation in a family with dominant myeloneuropathy. ### The surgically remediable syndrome of epilepsy associated with bottom-of-sulcus dysplasia![Graphic][1]</img> Patients with bottom-of-sulcus dysplasia (BOSD) often had a relapsing-remitting pattern of focal seizures and interictal EEG discharges, with long seizure remissions in response … [1]: /embed/inline-graphic-1.gif

Factors contributing to the yield of asymmetric bilateral implantation of intracranial electrodes.

To determine the outcome of implanting fewer electrodes over the hemisphere with less supporting presurgical localizing data. We retrospectively reviewed our epilepsy surgery database at Mayo Clinic, Rochester, Minnesota, between January 1, 1999, and December 31, 2011, to identify patients who had an asymmetric number of electrode contacts implanted in each hemisphere for seizure localization. We scored each presurgical noninvasive data point (0, 0.5, or 1) to predict the likelihood of identifying seizure onset in the hemisphere with fewer intracranial electrode contacts (HFEC). An aggregate score was obtained for each patient. Thirteen (37%) of 35 patients had HFEC-onset seizures on intracranial electroencephalography (iEEG). The following factors predicted HFEC-onset seizures: (1) temporal lobe epilepsy (p = 0.02); (2) interictal scalp electroencephalographic discharges at the HFEC (p = 0.04); and (3) both interictal and ictal scalp EEG discharges at the HFEC (p = 0.01). The median (range) aggregate score was 2 (1-3) for patients with HFEC-onset seizures recorded on iEEG and 1 (0-3) for patients without HFEC-onset seizures (p = 0.001). Using this scoring model, the odds ratio of identifying HFEC-onset seizures on iEEG was 6.4 for each one-point increment in the aggregate score. The area under the receiver operating characteristic curve for this model was 0.84, suggesting excellent ability of the aggregate score to discriminate between patients with and without HFEC-onset seizures on iEEG. Implanting electrodes on the basis of limited supporting presurgical data may be useful in selected patients, especially those with temporal lobe epilepsy, interictal scalp discharges involving the HFEC, or both interictal and ictal scalp discharges involving the HFEC. In addition, our proposed scoring system may be helpful in selecting patients with complicated epilepsy for implantation of an asymmetric number of intracranial electrodes in the hemispheres.

Magnetoencephalography helps delineate the extent of the epileptogenic zone for surgical planning in children with intractable epilepsy due to porencephalic cyst/encephalomalacia.

Porencephalic cyst/encephalomalacia (PC/E) is a brain lesion caused by ischemic insult or hemorrhage. The authors evaluated magnetoencephalography (MEG) spike sources (MEGSS) to localize the epileptogenic zone in children with intractable epilepsy secondary to PC/E. The authors retrospectively studied 13 children with intractable epilepsy secondary to PC/E (5 girls and 8 boys, age range 1.8-15 years), who underwent prolonged scalp video-electroencephalography (EEG), MRI, and MEG. Interictal MEGSS locations were compared with the ictal and interictal zones as determined from scalp video-EEG. Magnetic resonance imaging showed PC/E in extratemporal lobes in 3 patients, within the temporal lobe in 2 patients, and in both temporal and extratemporal lobes in 8 patients. Magnetoencephalographic spike sources were asymmetrically clustered at the margin of PC/E in all 13 patients. One cluster of MEGSS was observed in 11 patients, 2 clusters in 1 patient, and 3 clusters in 1 patient. Ictal EEG discharges were lateralized and concordant with MEGSS in 8 patients (62%). Interictal EEG discharges were lateralized and concordant with MEGSS hemisphere in 9 patients (69%). Seven patients underwent lesionectomy in addition to MEGSS clusterectomy with (2 patients) and without (5 patients) intracranial video-EEG. Temporal lobectomy was performed in 1 patient and hemispherectomy in another. Eight of 9 patients achieved seizure freedom following surgery. Magnetoencephalography delineated the extent of the epileptogenic zone adjacent to PC/E in patients with intractable epilepsy. Complete resection of the MEGSS cluster along with PC/E can provide favorable seizure outcomes.

Is interictal EEG activity a biomarker for mood disorders in temporal lobe epilepsy?

ObjectivePsychiatric comorbidities are frequent in temporal lobe epilepsy (TLE), and symptoms of these comorbidities may be related to epilepsy activity. Here we evaluated interictal EEG activity in TLE patients with or without psychiatric comorbidities. MethodsA cohort study of 78 patients with TLE, with evaluation of wake/sleep interictal scalp EEG. All subjects were submitted to a psychiatric structured clinical interview (SCID) for the diagnosis of lifetime psychiatric comorbidities. Three major diagnostic categories were studied: mood disorders, anxiety disorders, and psychosis. We then evaluated differences in interictal EEG activity between patients with and without these psychiatric comorbidities. ResultsInfrequent EEG interictal spikes, defined as less than one event per minute, were significantly associated with mood disorders in TLE (p=0.02). ConclusionsLow intensity seizure disorder has been associated with a decrease in interictal EEG discharges and with an increase in psychiatric symptoms in TLE, a phenomenon known as forced normalization. In our study, we observed a low interictal spike frequency on EEG in TLE patients with mood disorders. SignificanceA low spike index might be a neurophysiological marker for depression in temporal lobe epilepsy.

Transitory effect of spike and spike-and-wave discharges on EEG power in children

Background: Spikes and spike-and-wave discharges on the EEG of children are a strong biomarker of epilepsy. There is increasing evidence that these EEG abnormalities also impair brain function and result in transitory cognitive impairment. Studies in animal models have shown that EEG spikes alters single cell firing and that such impairment in firing may extend beyond the duration of the spike-and-wave discharge. Whether interictal epileptiform discharges have lasting effects on EEG activity in humans is not known. Methods and Results: The EEGs of 60 consecutive children with focal or interictal spike-and-wave discharges were evaluated using power spectral analysis to determine if there were any changes in power spectra from before to after the interictal abnormalities. Neither focal spike-and-wave nor generalized spike-and-wave discharges had any effect on the EEG frequency or spectral power following the discharge. Conclusion: While interictal EEG discharges temporarily alter neural activity during the duration of the spike-and-wave discharge, there is no evidence that alterations of spectral power continue beyond the duration of the interictal discharge. The effects of interictal activity on EEG rhythms therefore appear to be quite transient and confined to the duration of the interictal discharge.

Feasibility of focal transcranial DC polarization with simultaneous EEG recording: Preliminary assessment in healthy subjects and human epilepsy

We aimed to investigate the feasibility of an experimental system for simultaneous transcranial DC stimulation (tDCS) and EEG recording in human epilepsy. We report tolerability of this system in a cross-over controlled trial with 15 healthy subjects and preliminary effects of its use, testing repeated tDCS sessions, in two patients with drug-refractory Continuous Spike-Wave Discharges During Slow Sleep (CSWS). Our system combining continuous recording of the EEG with tDCS allows detailed evaluation of the interictal activity during the entire process. Stimulation with 1mA was well‐tolerated in both healthy volunteers and patients with refractory epilepsy. The large reduction in interictal epileptiform EEG discharges in the two subjects with epilepsy supports further investigation of tDCS using this combined method of stimulation and monitoring in epilepsy. Continuous monitoring of epileptic activity throughout tDCS improves safety and allows detailed evaluation of epileptic activity changes induced by tDCS in patients.