Interictal Epileptiform Discharges In Patients Research Articles

Termination of convulsion seizures by destabilizing and perturbing seizure memory engrams.

Epileptogenesis, arising from alterations in synaptic strength, shares mechanistic and phenotypic parallels with memory formation. However, direct evidence supporting the existence of seizure memory remains scarce. Leveraging a conditioned seizure memory (CSM) paradigm, we found that CSM enabled the environmental cue to trigger seizure repetitively, and activating cue-responding engram cells could generate CSM artificially. Moreover, cue exposure initiated an analogous process of memory reconsolidation driven by mammalian target of rapamycin-brain-derived neurotrophic factor signaling. Pharmacological targeting of the mammalian target of rapamycin pathway within a limited time window reduced seizures in animals and interictal epileptiform discharges in patients with refractory seizures. Our findings reveal a causal link between seizure memory engrams and seizures, which leads us to a deeper understanding of epileptogenesis and points to a promising direction for epilepsy treatment.

Omitting Hyperventilation in Electroencephalogram during the COVID-19 Pandemic May Reduce Interictal Epileptiform Discharges in Patients with Juvenile Myoclonic Epilepsy.

Background: To prevent the spread of coronavirus disease 2019 (COVID-19), hyperventilation (HV) activation has been avoided in electroencephalograms (EEGs) since April 2020. The influence of omitting HV in EEG on epilepsy diagnosis remains uncertain for patients with epilepsies other than child absence epilepsy. We hypothesized that EEGs with HV would show more interictal epileptiform discharges (IEDs) than EEGs without HV in patients with juvenile myoclonic epilepsy (JME). Methods: We reviewed the EEGs of seizure-free patients with JME who underwent EEG, both with and without HV, from January 2019 to October 2021, in our institution, and compared IEDs between EEG with and without HV. Results: This study analyzed 23 JME patients. The IED-positive rate was significantly higher in EEG with HV (65.2%) than in EEG without HV (34.8%, p = 0.016). The mean ± standard deviation number of IEDs per minute was significantly larger during HV (1.61 ± 2.25 × 10−1) than during non-activation of both first EEG (0.57 ± 0.93 × 10−1, p = 0.039) and second EEG (0.39 ± 0.76 × 10−1, p = 0.009). Conclusions: In JME patients, performing HV during EEG may increase IEDs and appears to facilitate the accurate diagnosis of epilepsy.

Therapeutic efficacy of seizure onset zone-targeting high-definition cathodal tDCS in patients with drug-resistant focal epilepsy

ObjectiveEpilepsy is a common neurological disease with recurrent seizures. Transcranial direct-current stimulation (tDCS) is a safe, non-invasive method used for neuromodulation. The aim of this study was to explore the efficacy of cathodal high-definition tDCS (HD-tDCS) as a noninvasive method for the treatment of patients with drug-resistant focal epilepsy (DRFE). MethodsThis study was conducted as a randomized parallel and double-blind clinical trial. Twenty patients with DRFE were randomly selected through the convenience sampling method and then were divided into two groups. Ten patients received 2 mA cathodal HD-tDCS targeting the seizure-onset zone for 30 min for 2 weeks (5 consecutive days in each week and 10 days in total). Ten patients were randomized to the sham group. Seizure frequency and Interictal Epileptiform Discharges (IEDs) frequency were the primary outcome measures of this study. Quality of Life in Epilepsy Inventory (QoLIE-89) and Montreal Cognitive Assessment (MoCA) scores were used as secondary outcome measures. ResultsSeizure frequency decreased significantly among the patients in the treatment group 2 weeks (P-value ≤ 0.05), 1 month (P-value ≤ 0.05), and 2 months (P-value ≤ 0.05) after the stimulation in comparison to the sham group. Patients in the treatment group showed a decrease in the frequency of IED 2 weeks (P-value ≤ 0.05), 1 month (P-value ≤ 0.05), and 2 months (P-value ≤ 0.05) after stimulation. This cathodal stimulation protocol also improved the overall QoLIE-89 score after the stimulation compared to the sham group. ConclusionsThe present study showed that cathodal HD-tDCS had a positive effect on seizure frequency and IED in patients with DRFE. More evidence is required to define the optimal stimulation parameters of HD-tDCS for the treatment of epilepsy. SignificanceCathodal HD-tDCS targeting the seizure-onset zone is a promising treatment modality for patients with drug-resistant focal epilepsy.

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

ObjectiveTo 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). MethodsWe 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. ResultsIEDs 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. ConclusionsEEG recordings using NPEs are useful to improve the sensitivity and level of agreement among interpreters for the detection of IEDs in patients with TLE. SignificanceNPE recordings may be recommended in routine EEGs for the evaluation of patients with suspected TLE.

The Effect of Cognitive Tasks During Electroencephalography Recording in Patients With Reflex Seizures.

We aimed to research the effect of cognitive tasks on interictal electroencephalographic (EEG) recordings in patients with epilepsy who had reported cognitive functions as a seizure trigger. We investigated the usefulness of cognitive function tasks as a method of activation in standard-awake EEG in daily practice. Standard-awake EEG with cognitive activation tasks consisting of verbal and arithmetic tasks was administered to 35 (11.7%) of 299 patients with epilepsy who reported cognitive functions as a reflex seizure stimulus. During the background EEG, patients were divided into 2 groups: group 1 (17 patients) with interictal epileptiform discharges (IEDs), and group 2 (18 patients) without IEDs. IEDs were activated by a verbal task in 11.4% of patients and by an arithmetic task in 5.7%. All activated patients were in the genetic/idiopathic generalized epilepsy (IGE) group. In group 1, IEDs were activated in 17.6% of patients by a verbal task and in 5.9% by an arithmetic task. Both verbal and arithmetic tasks showed provocative effect in one patient in group 2. Hyperventilation was the most effective activation method, followed by cognitive activation tasks and photic stimulation. The provocative effects of verbal and arithmetic tasks were comparable to those of photic stimulation. Cognitive tasks might activate the IEDs in patients reporting cognitive functions as a seizure trigger, particularly in IGE. Brief and standardized cognitive activation tasks should be developed and applied as a method of activation during standard-awake EEG recordings to increase the diagnostic yield of EEG.

Interictal epileptiform discharges vary across age groups

ObjectiveTo investigate whether the occurrence and morphology of interictal epileptiform discharges (IEDs) in scalp-EEG change by age. Methods10,547 patients who had a standard or sleep deprived EEG recording reported using the SCORE standard were included. 875 patients had at least one EEG with focal IEDs. Focal IED morphology was analyzed by age using quantitative measures in EEGLAB and by visual classification based on the SCORE standard. We present distributions of IED measures by age group, with medians, interquartiles, 5th and 95th percentiles. ResultsFocal IEDs occurred most frequently in children and elderly. IED morphology and localization depended on age (p < 0.001). IEDs had higher amplitudes, sharper peaks, larger slopes, shorter durations, larger slow-wave areas and wider distributions in children. These morphological characteristics diminished and the IEDs became more lateralized with increasing age. Spike asymmetry was stable across all age groups. ConclusionsIEDs have age-dependent characteristics. A spike detector, human or computer, should not operate with the same set of thresholds for patients at various age. With increasing age, focal IEDs are less sharp, have lower amplitudes, have less prominent slow-waves and they become more lateralized. Our findings can help EEG readers in detecting and correctly describing IEDs in patients of various age. SignificanceEEG readers should always consider patient age when interpreting interictal epileptiform discharges.

Monitoring time of interictal epileptiform discharges by long-term video EEG in patients with epilepsy

Objective: To optimize the monitoring time of interictal epileptiform discharges (IED) in patients with epilepsy by long-term video electroencephalogram (VEEG). Methods: The cumulative percentages of IED detected by VEEG in 346 epilepsy patients (349 times) with different purposes, different waking sleep states and different MRI findings were retrospectively analyzed. According to the purposes, there were 164 patients (165 times) for clarifying diagnosis, 124 patients (124 times) for preoperative evaluation and 58 patients (60 times) for adjustment of medications. According to MRI results, there were responsible lesions in 98 patients (98 times) and no responsible lesions in 173 patients (174 times). Results: Among 346 patients (349 times), IED was detected within 24 h in 231 patients (times). The percentage of detection in patients with purpose of preoperative evaluation was higher than those with purpose of diagnosis and medication adjustment. The detection of LED was gradually increased in first 8 h with 59.0%, then stably in 24 h. 46.8% IED was recorded during sleep time, particularly in the second stage of sleep. The cumulative percentage of IED in patients with abnormal MRI findings was higher in all periods. It reached 83.7% within 8 h, and then tended to be stable. Conclusion: The study shows that LED should be monitored by VEEG at least 8 hours and should include the second stage of sleep in patients with epilepsy. Patients with refractory epilepsy and with abnormal lesions on MRI should record IED more frequently.

Impaired Executive Function by Interictal Epileptiform Discharges in Patients with Idiopathic Generalized Epilepsy

Objective: Many patients with Idiopathic Generalized Epilepsy (IGE) exhibit cognitive deficits. Interictal Epileptiform Discharges (IEDs) may contribute to cognitive impairment in epilepsy; however, the relationship between IEDs and cognitive impairment is unclear. Methods: In this study, we analysed executive function in three groups: IGE patients with IEDs, IGE patients without IEDs and healthy controls. Executive function was assessed using the Stroop Test, the Verbal Fluency Test, the Digit Span Test and Wisconsin Card-Sorting Test. Results: The IGE patients with IEDs performed worse on executive function tests compared with patients without IEDs. Furthermore, the IGE patients without IEDs performed worse compared with healthy controls. There were significant differences between the three groups in performance on the Stroop Test, the Digit Span Test (forward and backward), Verbal Fluency Test (animals, fruits) and the subscales of WCST (Categories Completed, Correct Response, Total Errors and Preservative Errors). Conclusion: These results suggest that executive function in patients with IGE is impaired and is further impaired by IEDs. Future studies should determine whether well-controlled patients with IGE could benefit from antiepileptic treatment.

EEG–fMRI in focal epilepsy: Local activation and regional networks

ObjectiveTo identify features of BOLD signal change associated with interictal epileptiform discharges (IEDs) in a heterogeneous group of focal epilepsy patients. MethodsEEG/fMRI studies in 27 focal epilepsy patients were reviewed with attention given to the extent and location of the IED and the resulting pattern of BOLD signal change. Second order group analysis was used to identify common features. ResultsfMRI results provided novel clinical information for individual patients. We identified a significant common node within the ipsilateral piriform cortex as well as patterns involving distant cortical or subcortical areas. ConclusionDespite the heterogeneity of IEDs in focal epilepsy, there are important common features underpining IEDs with a highly significant fMRI node in the ipsilateral piriform cortex. SignificanceThere are important common features in the networks involved in IEDs in patients with a heterogeneous range of epileptogenic foci. We confirm that the piriform cortex is a common node underlying IEDs in patients with focal epilepsy and so provides a target for further study and potential therapy. We describe important features of BOLD signal change that accompany focal and diffuse IEDs that will help researchers and clinicians navigate the sometimes complex findings revealed by these studies.

A study on circadian rhythm of interictal epileptiform discharges in patients with localization related epilepsy

Objective To investigate the effects of circadian rhythm on interictal epileptiform discharges in patients with localization-related epilepsy. Methods Patients diagnosed with epilepsy in Sanbo Brain Hospital from January 2011 to January 2012 participated in this study.All patients were subjected to comprehensive evaluation, which included prolonged video-electroencephalogram (EEG), magnetic resonance imaging. Intracranial electrodes, PET, SPECT were also adopted if necessary. Circadian rhythm was divided into four stages: REM, NREM I-II, NREM III-IV, and waking.The amount and distribution of IID were compared by ANOVA. Results Significant differences in the amount and distribution of IID were found among NREM I-II, NREM III-IV, REM, and waking. However, no differences in the amount and distribution of IID were noted between NREM I-II and NREM III-IV as well as between REM and waking. Conclusion The amount of IID is higher in NREM than in REM and waking; thus, NREM is more sensitive to diagnose epilepsy.The distribution of IID in REM and waking is more restricted than that in NREM. Key words: 【Key word】 Interictal epileptiform discharges; Epilepsy; Sleep; Circadian rhythm

EEG-Langzeit-Monitoring - Indikationen und Limitationen im prächirurgischen Monitoring

Epilepsy may be difficult to diagnose at first. Video-EEG Monitoring has two main indications: to assure or reject the diagnosis of epilepsy or to localize the seizure onset zone. Interictal epileptiform discharges (IEDs) are essential in classifying epilepsies. However, knowledge on the latency of IEDs is incomplete. The aim of this study was to assess the latency of IEDs and seizures in long-term EEG recordings of patients with epilepsy and therefore shed some light on the limitations of Video-EEG recordings. We analyzed the latency of IEDs and seizures from video-EEGs of 101.5 ± 62.7 hours (median ± SD) duration in 210 consecutive patients (94 male; age 38.6 ± 13.9 years) with active (median 3.5 seizures/month) epilepsy (176 structural-metabolic, 25 genetic, epilepsy duration 16.4 ± 13.7 years). Variables were age, duration of epilepsy, frequency of seizures and medication, the sleep state with IEDs, and their relation to seizures. Findings: Median spike latency was 9.3 ± 23.9 hours (within 20 min, 30 min, 24, 48, and 72 hours in 7.3%, 9.7%, 74.5%, 87.9%, and 98.2% respectively). Frequency of seizures, number of AEDs, etiology, age of onset or duration of epilepsy, and epilepsy syndrome did not correlate with spike latency. Of ninety patients with temporal lobe epilepsy IEDs were present in 95.6%. We did not find IEDs in 21.4% of long-term recorded patients, despite seizures in half of them. In other words, 21 patients with a seizure had no IED. Conclusion: Long-term EEG recordings of 72h in almost all cases should be sufficient to determine the presence of IEDs in patients with unclear paroxysmal events. Still, one in five patients will not have any IEDs even with EEG of long duration. Since IEDs are not uncommon in nonepileptic events and since one in 10 will not have seizures or IEDs, longer lasting EEGs or video records of habitual events should be mandatory in critical patients to minimize false negative studies.

Effect of chronic vagal nerve stimulation on interictal epileptiform discharges

We evaluated the effect of vagus nerve stimulation (VNS) on interictal epileptiform discharges (IEDs) in 32 epileptic patients (18 females; 14 males) with an average age of 42.2 ± 11.4 years, all of whom had been suffering from epilepsy for an average of 29.2 ± 14.5 years. All of the patients had received VNS for 5 years. The first EEG was performed prior to the initiation of stimulation; the second EEG was performed at the 5-year follow-up visit. The duration of each EEG was 30 min. We compared these two EEGs in terms of the number of IEDs present in each patient and correlated them to other variables. The average total number of IEDs during EEG and the total number of seconds in which IEDs were present decreased significantly after 5 years of stimulation from 97.3 ± 106.9 resp. 80.6 ± 86.1 to 49.4 ± 94.0 resp. 37.8 ± 65.0. Although there was no positive correlation between the reduction of IEDs and the percent of seizure reduction, we found a greater decrease of IEDs in patients who responded to VNS in comparison to those who did not. The decrease of IEDs was more pronounced in patients suffering from temporal lobe epilepsy than in patients suffering from extratemporal epilepsy. No other significant correlations were found. VNS reduced IEDs in patients chronically simulated for epilepsy. The reduction of IEDs was greater in patients who responded to VNS and in patients suffering from temporal lobe epilepsy.

The Yield of Routine Outpatient Electroencephalograms in the Veteran Population

The objective of this study is to determine the yield of routine outpatient electroencephalogram (EEG) in the diagnosis of epilepsy in the veteran population. All consecutive outpatient EEGs at the James A. Haley Veterans Affairs Hospital in Tampa, FL from October 31, 2005, to October 30, 2007, were retrospectively reviewed. During the 2 years of the study, 636 routine outpatient EEGs were performed at James A. Haley Veterans Affairs Hospital. The age range for the patients was 21 to 97 years with a mean age of 55 years. Eighty-five EEGs (13.4%) were classified as abnormal. Nineteen EEGs (3%) in the past 2 years contained epileptiform abnormalities. Sixty-eight EEGs (10.7%) had other abnormalities such as slowing, asymmetry, excessive beta activity, or a combination of abnormalities. Thirty-six EEGs (5.7%) clearly demonstrated psychogenic nonepileptic attacks as documented by normal EEG and video recording of the patient's habitual event. Single routine outpatient EEG has been reported to have a sensitivity of 29% to 55% in detecting interictal epileptiform discharges in patients with a suspected diagnosis of epilepsy. In our study, only about 3% of the patients had clear abnormalities suggestive of epilepsy. Interestingly, by using routine EEGs, we were able to definitively diagnose more patients with psychogenic nonepileptic attacks than epileptic seizures.

Low-frequency electric cortical stimulation decreases interictal and ictal activity in human epilepsy

We previously reported that low-frequency electric cortical stimulation (LFECS) directly applied to the epileptic focus by means of subdural electrodes decreased the number of interictal epileptiform discharges in patients with intractable partial epilepsy. In the present study, LFECS was applied to the epileptic foci directly in four patients with medically intractable partial epilepsy through subdural electrodes and evaluated its effect on the number of interictal epileptiform discharges as well as simple partial seizures. We used alternating electric current of 0.3 ms duration presented at 0.9 Hz frequency for 250 s. LFECS did not induce seizures in any of the four patients. In one patient, the number of interictal epileptiform discharge decreased significantly by LFECS, which is in conformity with our previous report. In addition, LFECS applied to the seizure onset zone decreased the frequency of simple partial seizures in one patient. These results suggest that LFECS has an inhibitory effect not only on the interictal but also the ictal activities in patients with intractable partial epilepsy. Further study is required to determine the inhibitory effect of LFECS more in details.

Source localization of small sharp spikes: Low resolution electromagnetic tomography (LORETA) reveals two distinct cortical sources

Objective We have investigated the cortical sources and electroencephalographic (EEG) characteristics of small sharp spikes (SSS) by using statistical non-parametric mapping (SNPM) of low resolution electromagnetic tomography (LORETA). Methods We analyzed 7 SSS patterns (501 individual SSS) in 6 patients who underwent sleep EEG studies with 29 or 23 scalp electrodes. The scalp signals were averaged time-locked to the SSS peak activity and subjected to SNPM of LORETA values. Results All 7 SSS patterns (mean 72 individual SSS, range 11–200) revealed a very similar and highly characteristic transhemispheric oblique scalp voltage distribution comprising a first negative field maximum over ipsilateral lateral temporal areas, followed by a second negative field maximum over the contralateral subtemporal region approximately 30 ms later. SNPM–LORETA consistently localized the first component into the ipsilateral posterior insular region, and the second component into ipsilateral posterior mesial temporo-occipital structures. Conclusions SSS comprise an amalgam of two sequential, distinct cortical components, showing a very uniform and peculiar EEG pattern and cortical source solutions. As such, they must be clearly distinguished from interictal epileptiform discharges in patients with epilepsy. Significance The awareness of these peculiar EEG characteristics may increase our ability to differentiate SSS from interictal epileptiform activity. The finding of a posterior insular source might serve as an inspiration for new physiological considerations regarding these enigmatic waveforms.

EEG quantitative analysis in patients with rolandic epileptiform discharges

The importance of localization and morphologic features of interictal epileptiform discharges in patients suspected of having epileptic seizures is well known. Rolandic discharges (RD) have been reported in association to benign rolandic epilepsy of childhood (BREC), a common type of epilepsy in children that has well defined clinical features, familiar traces, no neurological lesion and good prognosis. These patients present an EEG with normal background activity on visual analysis […] EEG quantitative analysis in patients with rolandic epileptiform discharges

Failure of Naloxone to Modify Electroencephalogram Interictal Epileptiform Discharges in Patients with Primary Generalized Epilepsy After Sleep Deprivation

Sleep deprivation (SD) is a method widely used to activate EEG epilept oform activity, but the basis of this effect remains unknown. One possibilty is that SD shares a common mechanism with physical and psychological stresses that also precipitate seizures. Because endogenous opioids are released during stress, opioids may play a role in enhancing epileptiform EEG patterns after SD. We report the effects of SD on EEG epileptiform activity in a small but highly homogeneous population of 13 epileptic patients with idiopathic (primary) generalized epilepsy (IGE). SD increased EEG interictal epileptiform discharges (IEDs); this activation was not modified by naloxone (NAL). Our results, in contrast to those of previous investigations of localization-related epilepsy, which showed an increase in IEDs after NAL administration, suggest a possible difference in the mechanism whereby SD enhances IEDs in IGE and localization-related epilepsy.