Sleep-Wake Patterns of Seizures in Children With Lesional Epilepsy

This study examined diurnal patterns of seizures and their occurrence during wakefulness and sleep in children with lesional focal epilepsy. We reviewed 332 consecutive children with lesional focal epilepsy and video-electroencephalogram monitoring during a 3-year period. Data were analyzed in relationship to clock time, wakefulness/sleep, and seizure localization. The distribution of lesions in 66 children (259 seizures) included mesial temporal, 29%; neocortical temporal, 18%; frontal, 29%; parietal, 13.5%; and occipital, 12%. Seizures in patients with frontal lesions occurred mostly during sleep (72%). Seizures in mesial temporal (64%), neocortical temporal (71%), and occipital (66%) lesional epilepsy occurred mostly during wakefulness. Temporal lobe seizures occurred more frequently during wakefulness (66%), compared with extratemporal seizures (32%) (odds ratio, 2.67; 95% confidence interval, 1.61-4.42). Temporal lobe seizures peaked between 9:00 am and noon and 3:00-6:00 pm, whereas extratemporal seizures peaked between 6:00-9:00 am. Sleep, not clock time, provides a more robust stimulus for seizure onset, especially for frontal lobe seizures. Temporal lobe seizures are more frequent during wakefulness than are extratemporal seizures. Circadian patterns of seizures may provide additional diagnostic and treatment options, such as differential medication dosing and sleep-schedule adjustments.     

Absence of sleep spindles in human medial and basal temporal lobes

All-night recordings from subdural electrocorticographic (ECoG) electrodes on the human medial and basal temporal lobes were analysed to examine spindling activities during sleep. Subjects were three males and three females who were candidates for neurosurgical treatments of partial epilepsy. Subdural electrodes were attached to the medial and basal temporal lobe cortices, allowing ECoG and electroencephalogram from the scalp vertex (Cz EEG) to be recorded simultaneously during all night sleep. In one case, subdural electrodes were attached also on the parietal lobe. Fast Fourier transformation (FFT) analyses were performed on the ECoG and Cz EEG signals. No organized sleep spindles or sigma band (12-16 Hz) peaks in FFT power spectra were observed from the medial or basal temporal lobes of the non-epileptogenic hemispheres during non-rapid eye movement (NREM) sleep. In a case with parietal electrodes, organized spindle bursts were observed in parietal signals synchronized with Cz spindles. Although delta band (0.3-3 Hz) power from both the medial and basal temporal lobes fluctuated across each night as expected, sigma activity changed little. However, 14 Hz oscillatory bursts were observed in the medial basal temporal lobe of epileptogenic hemisphere in two cases and bilaterally in one case during not only NREM sleep but rapid eye movement (REM) sleep and wakefulness. From the present study we conclude that sleep spindle activities are absent in the medial and basal temporal lobes. Fourteen Hz oscillatory bursts observed from the medial or basal temporal lobe in some cases were not considered to be sleep spindles since they also appeared during REM sleep and wakefulness. These waveforms could have originated due to epileptic pathology, since they frequently appeared in epileptic regions.     

Electric cortical stimulation suppresses epileptic and background activities in neocortical epilepsy and mesial temporal lobe epilepsy.

OBJECTIVE: To evaluate the suppressive effect of electric cortical stimulation upon the seizure onset zone and the non-epileptic cortex covered by subdural electrodes in patients with neocortical epilepsy and mesial temporal lobe epilepsy (MTLE). METHODS: Four patients with medically intractable focal epilepsy had implanted subdural electrodes for preoperative evaluation. Cortical functional mapping was performed by intermittently repeating bursts of electric stimulation, which consisted of 50 Hz alternating square pulse of 0.3 ms duration, 1-15 mA, within 5 s. The effect of this stimulation on the seizure onset zones and on the non-epileptic areas was evaluated by comparing spike frequency and electrocorticogram (ECoG) power spectra before and after stimulation. A similar comparison was performed in stimulation of 0.9 Hz of the seizure onset zones for 15 min. RESULTS: When the seizure onset zone was stimulated with high frequency, spike frequency decreased by 24.7%. Logarithmic ECoG power spectra recorded at stimulated electrode significantly decreased in 10-32 Hz band by high frequency stimulation of the seizure onset zone, and in 14-32 Hz band by high frequency stimulation of the non-epileptic area. Low frequency stimulation of the seizure onset zone produced 18.5% spike reduction and slight power decrease in 12-14 Hz. CONCLUSIONS: Both high and low frequency electric cortical stimulation of the seizure onset zone have a suppressive effect on epileptogenicity. Reduction of ECoG fast activities after electric cortical stimulation suggests the augmentation of inhibitory mechanisms in human cortex.     

Factors affecting spiking related to sleep and wake states in temporal lobe epilepsy (TLE).

The aim of the study was to investigate the influence of different clinical factors on spiking during sleep and wakefulness in temporal lobe epilepsy. The study included 38 temporal lobe epilepsy (TLE) patients who underwent long-term electroencephalography (EEG) monitoring. In addition to traditional sleep scoring, waking was subdivided into eyes opened (WEO) and eyes closed (WEC) states. The following spike measures were investigated: spiking rates for each state, mean spike rate, spiking stability across wake and sleep states and relative spike density for each state. These measures were investigated according to clinical variables, such as age, age at epilepsy onset, duration of epilepsy, seizure frequency, the presence of secondarily generalised tonic-clonic (SGTC) seizures and the data on epileptogenic lesions based on MRI. Spiking rates during most states and spiking stability showed a significant positive correlation with epilepsy duration. Relative spike density during sleep stage NREM3,4 significantly increased with age at epilepsy onset. Relative spike density during WEC was significantly higher in the presence of hippocampal sclerosis (HS). Spiking rate during REM was significantly higher if a patient had SGTC seizures. Our data provide evidence that different aspects of spiking are associated with different aspects of TLE. We suggest that spike behaviour analysis offer new aspects both for diagnosis and research.     

Intracerebral recordings of nocturnal hyperkinetic seizures: demonstration of a longer duration of the pre-seizure sleep spindle.

OBJECTIVE: Nocturnal frontal lobe epilepsy (NFLE) seizures occur primarily during non-rapid eye movement sleep stage 2. We observed in several patients rhythms of same localization and frequency as sleep spindles, immediately preceding and sometimes continuing at seizure onsets. We aimed to study the link between sleep spindles and seizure onsets. METHODS: We used intracerebral stereo-EEG ictal recordings of two MRI-negative patients with clinically defined NFLE. For each of the six studied seizures, sustained activity in the frontal sleep spindle frequency (12Hz) was observed around seizure onset. The duration of this pre-seizure sleep spindle was compared to that of the 10 preceding sleep spindles. RESULTS: The pre-seizure sleep spindles were clearly of longer duration than the "interictal" sleep spindles for all seizures. This sustained pre-seizure 12Hz activity could be differentiated from normal awakenings, and showed no spatial relation to the ictal onset. CONCLUSIONS: We demonstrated a functional alteration of the sleep spindle-generating thalamocortical loop concomitant with the seizure onsets. This defect may also be involved in seizure generation. SIGNIFICANCE: A thalamic participation in NFLE pathogenesis is likely in our two patients. The study of additional patients will allow to evaluate the role of the thalamocortical circuits in NFLE.     

Ictal scalp EEG recording during sleep and wakefulness: diagnostic implications for seizure localization and lateralization

To determine the localizing value of electroencephalography (EEG) for seizures during sleep versus seizures during wakefulness, we compared scalp EEG for 58 seizures that occurred during sleep with 76 seizures during wake in 28 consecutive patients with temporal lobe epilepsy. Regression analysis showed that seizures during sleep are 2.5 times more likely to have focal EEG onset (p = 0.01) and 4 times more likely to correctly localize seizure onset (p = 0.04) than seizures during wake. EEG seizure onset preceded clinical onset by a longer duration in sleep seizures (mean, 4.69 s) than in wake seizures (mean, 1.23 s; p < 0.01). Sleep seizures showed fewer artifacts, but the difference was not significant (p = 0.07). For temporal lobectomy candidates undergoing video-EEG monitoring, the recording of seizures during sleep may be favored.     

Effects of Sleep and Sleep Stage on Epileptic and Nonepileptic Seizures

Summary: Purpose: Previous studies of patients with epilepsy and animal models of epilepsy suggest that sleep increases the frequency, duration, and secondary generalization of seizures. This information is, however, incomplete.
Methods: We retrospectively examined video-EEG monitoring reports from our comprehensive epilepsy center. We recorded seizure type, site of onset (for partial seizures), sleep state at onset, and whether partial seizures secondarily generalized. Seizures arising from sleep were then reviewed to determine sleep state.
Results: We analyzed 1,116 seizures in 188 patients. Thirty-five percent of complex partial seizures (CPSs) starting during sleep underwent secondary generalization compared with 18% in wakefulness (p < 0.0001). Frontal lobe CPSs secondarily generalized at equal rates during sleep (22%) and wakefulness (20%), but temporal lobe CPSs generalized much more frequently during sleep (45%) than in wakefulness (19%; p < 0,0001). Frontal lobe seizures were more likely to occur during sleep (37%) than were temporal lobe seizures (26%; p = 0.0068). CPSs were more frequent in stages 1 and 2 and occurred rarely during REM. Seizures starting during slow-wave sleep were significantly longer than seizures starting during wakefulness or stage 2 sleep. Psychogenic nonepileptic seizures (PNESs) were rare between midnight and 6 a.m. and never occurred during sleep.
Conclusions: Sleep has a pronounced effect on secondary generalization of partial seizures, especially those of temporal lobe origin. Frontal lobe seizures occur more often during sleep than do temporal lobe seizures, and occurrence during sleep helps to distinguish PNESs from CPSs.     

Focal Sleep Spindle Deficits Reveal Focal Thalamocortical Dysfunction and Predict Cognitive Deficits in Sleep Activated Developmental Epilepsy

Childhood epilepsy with centrotemporal spikes (CECTS) is the most common focal epilepsy syndrome, yet the cause of this disease remains unknown. Now recognized as a mild epileptic encephalopathy, children exhibit sleep-activated focal epileptiform discharges and cognitive difficulties during the active phase of the disease. The association between the abnormal electrophysiology and sleep suggests disruption to thalamocortical circuits. Thalamocortical circuit dysfunction resulting in pathologic epileptiform activity could hinder the production of sleep spindles, a brain rhythm essential for memory processes. Despite this pathophysiologic connection, the relationship between spindles and cognitive symptoms in epileptic encephalopathies has not been previously evaluated. A significant challenge limiting such work has been the poor performance of available automated spindle detection methods in the setting of sharp activities, such as epileptic spikes. Here, we validate a robust new method to accurately measure sleep spindles in patients with epilepsy. We then apply this detector to a prospective cohort of male and female children with CECTS with combined high-density EEGs during sleep and cognitive testing at varying time points of disease. We show that: (1) children have a transient, focal deficit in spindles during the symptomatic phase of disease; (2) spindle rate anticorrelates with spike rate; and (3) spindle rate, but not spike rate, predicts performance on cognitive tasks. These findings demonstrate focal thalamocortical circuit dysfunction and provide a pathophysiological explanation for the shared seizures and cognitive symptoms in CECTS. Further, this work identifies sleep spindles as a potential treatment target of cognitive dysfunction in this common epileptic encephalopathy.SIGNIFICANCE STATEMENT Childhood epilepsy with centrotemporal spikes is the most common idiopathic focal epilepsy syndrome, characterized by self-limited focal seizures and cognitive symptoms. Here, we provide the first evidence that focal thalamocortical circuit dysfunction underlies the shared seizures and cognitive dysfunction observed. In doing so, we identify sleep spindles as a mechanistic biomarker, and potential treatment target, of cognitive dysfunction in this common developmental epilepsy and provide a novel method to reliably quantify spindles in brain recordings from patients with epilepsy.     

Two magneto-encephalographic epileptic foci did not coincide with the electrocorticographic ictal onset zone in a patient with temporal lobe epilepsy.

To evaluate the usefulness and limitations of magneto-encephalography (MEG) for epilepsy surgery, we compared 'interictal' epileptic spike fields on MEG with ictal electrocorticography (ECoG) using invasive chronic subdural electrodes in a patient with intractable medial temporal lobe epilepsy (MTLE) associated with vitamin K deficiency intracerebral hemorrhage. A 19-year-old male with an 8-year history of refractory complex partial seizures, secondarily generalized, and right hemispheric atrophy and porencephaly in the right frontal lobe on MRI, was studied with MEG to define the interictal paroxysmal sources based on the single-dipole model. This was followed by invasive ECoG monitoring to delineate the epileptogenic zone. MEG demonstrated two paroxysmal foci, one each on the right lateral temporal and frontal lobes. Ictal ECoG recordings revealed an ictal onset zone on the right medial temporal lobe, which was different from that defined by MEG. Anterior temporal lobectomy with hippocampectomy was performed and the patient has been seizure free for two years. Our results indicate that interictal MEG does not always define the epileptogenic zone in patients with MTLE.     

Spike frequency is dependent on epilepsy duration and seizure frequency in temporal lobe epilepsy.

OBJECTIVES: We wanted to investigate factors that are associated with frequency of interictal epileptiform discharges by investigating 303 patients with temporal lobe epilepsy (TLE). METHODS: We included all patients who consecutively underwent the adult presurgical evaluation program at our center and who had intractable, medial TLE with complex partial seizures due to unilateral medial temporal lobe lesions. The interictal EEG samples were automatically recorded and stored on computer. The location and frequency of interictal epileptiform discharges were assessed by visual analysis of interictal EEG samples of 2-minute duration every hour. RESULTS: There were 303 patients (aged 16-63) who met the inclusion criteria. The median interictal epileptiform discharge frequency was 15 IED/h, the median seizure frequency was 4 seizures/month. According to univariate analyses, we found that age at monitoring, epilepsy duration, and higher seizure frequency were associated with higher interictal epileptiform discharge frequency. In the logistic regression analysis, we found that higher seizure frequency (p < 0.001) and longer epilepsy duration (p = 0.007) were independently associated with higher spike frequency, while the age at monitoring was not. CONCLUSIONS: Seizure frequency and epilepsy duration (years of patient's life with seizure activity) were independently associated with IED frequency, suggesting that IED are modulated by seizures.     

The cessation of continuous spike wave in slow-wave sleep following a temporal lobectomy

The role of surgery in continuous spike wave in slow-wave sleep has not been robustly explored. The authors present a case of an 11-year-old boy with refractory partial seizures and continuous spike wave in slow-wave sleep who was treated with an anterior temporal lobectomy. His presurgical brain magnetic resonance imaging revealed right basal ganglia and thalamic infarcts and right mesial temporal sclerosis. Following surgery, he achieved seizure freedom, cessation of continuous spike wave in slow-wave sleep, and improved cognition. This case provides further evidence that epilepsy syndromes with generalized electrographic discharges can be secondary to focal pathology and potentially cured with resective surgery. The normalization of his sleep electroencephalogram following the anterior temporal lobectomy suggests that temporal lobe structures may be involved in the seizure network needed to generate continuous spike wave in slow-wave sleep.     

Predicting diurnal and sleep/wake seizure patterns in paediatric patients of different ages

Aim. To identify factors that influence diurnal and sleep/wake seizure timing in children undergoing tapered drug withdrawal in an epilepsy monitoring unit. Methods. Medical charts of patients that underwent video‐EEG were reviewed. Seizures were evaluated based on their occurrence in three‐hour time intervals (bins) and between wakefulness and sleep. Patients were classified according to EEG localisation and age: infants (≤3 years), children (3–12 years), and adolescents (>12–21 years). Analysis utilising generalised estimating equations with a negative binomial distribution was performed. Results. A total of 390 patients (188 girls; mean age: 9.2 years; SD: 6.0) had 1,754 seizures. Generalised seizures (109 patients; 490 seizures) occurred more during wakefulness (p<0.001) and during the day (p<0.001). Modelling revealed a greater occurrence of seizures at night with increasing age (p=0.046). Temporal lobe seizures (62 patients; 271 seizures) occurred overall more frequently during wakefulness (p=0.03). Frontal lobe seizures (41 patients; 184 seizures) occurred more frequently during wakefulness in infants (p<0.05) and more frequently during sleep in adolescents (p<0.0001). Adolescents with frontal lobe seizures were 3.6 times more likely to have seizures during sleep compared to other children (95% CI: 1.8–7.2). Conclusion. These findings are suggestive of changes in circadian rhythmicity that may alter seizure susceptibility in different age groups. The results may assist in prediction of periods of greatest seizure propensity.     

Reduction of rapid eye movement sleep by diurnal and nocturnal seizures in temporal lobe epilepsy

BACKGROUND: Patients with brief, complex partial seizures frequently suffer from tiredness and decreased productivity that continue well beyond the postictal period. A possible explanation is that seizures, even when occurring during the day, disrupt sleep the following night. OBJECTIVE: To determine the effect of temporal lobe complex partial seizures on sleep structure and daytime drowsiness. METHODS: Patients with temporal lobe epilepsy were admitted for video-electroencephalography monitoring. All-night polysomnography was recorded under the following 3 conditions: seizure free, seizure during the day before the recording, and seizure during the recording. Percentage of time in each sleep stage, sleep efficiency, and time to first and second rapid eye movement (REM) period were compared for seizure vs control conditions. Daytime drowsiness was also measured, using a modified maintenance of wakefulness test and 2 subjective drowsiness tests. RESULTS: Daytime seizures reduced REM from 18%+/-1% to 12%+/-2% (P = .003). Night seizures reduced REM from 16%+/-1% to 6.8%+/-2% (P<.001). Night seizures also significantly reduced stages 2 and 4 while increasing stage 1 sleep. Night seizures, but not day seizures, significantly reduced sleep efficiency, increased time to first REM period, and increased drowsiness as measured by the maintenance of wakefulness test. CONCLUSIONS: Temporal lobe complex partial seizures decrease REM sleep, particularly when occurring during sleep but also when occurring on the previous day. This may, in part, be responsible for the prolonged impairment of functioning that some patients report following seizures.     

Thalamic kindling: electrical stimulation of the lateral geniculate nucleus produces photosensitive grand mal seizures

Kindling is traditionally viewed as a chronic, focal epilepsy model which consistently induces complex partial seizures from limbic structures in animals. This study revealed that primary or exceedingly rapid secondary generalized seizures could also be kindled when stimulation was applied to the lateral geniculate nucleus, a thalamic region involved in sleep regulation and possibly also photosensitive epilepsy. Two experiments were conducted in cats. Experiment 1 compared the development of generalized tonic-clonic convulsions and associated sleep disorders following electrical stimulation of the lateral geniculate nucleus (N = 4) and the amygdala (N = 4). Experiment 2 described the effects of intermittent light stimulation on seizure thresholds in both groups. Three primary findings distinguished the epileptogenic process in those two brain regions. First, generalized electroencephalographic and clinical seizures accompanied the first afterdischarge obtained with thalamic stimulation. In contrast, focal seizures with secondary generalization appeared during a 3- to 4-week period of afterdischarge elicitations from the amygdala. Second, amygdala-kindled cats showed fewer sleep spindles during slow-wave sleep whereas cats kindled in the lateral geniculate nucleus had abnormal sleep spindles approaching spike wave-like activity. Third, only the latter cats showed reduced seizure thresholds in response to photic stimulation. Based on the anatomic substrates involved, the clinical and electrographic profiles observed during kindling and the type of sleep disturbance shown, we concluded that lateral geniculate nucleus kindling may represent primary generalized epilepsy, possibly of a photosensitive nature; alternatively, the rapid propagation of abnormal discharge was also consistent with the important role of the thalamus in secondary seizure generalization.     

Is Intraoperative Electrocorticography Reliable in Children with Intractable Neocortical Epilepsy?

PURPOSE: To study the relation between the spike frequency during intraoperative electrocorticography (ECoG) under general anesthesia with isoflurane and that during extraoperative ECoG monitoring in children with intractable neocortical epilepsy. METHODS: Twenty-one children (age, 1-16 years; 15 boys and six girls) who underwent intraoperative and extraoperative ECoG monitoring with subdural electrode arrays were studied. The spike frequency and the spatial pattern of spike frequency were compared between intraoperative and extraoperative ECoGs for each patient (by using Wilcoxon signed-ranks and Spearman's rank correlation, respectively). RESULTS: In 15 of 21 patients, the spike frequency was significantly lower during intraoperative than during extraoperative ECoG (mean z = -6.3; p < 0.001). In four of 21 patients, no significant difference was found in the spike frequency between intraoperative and extraoperative recordings. In two of 21 patients, spike frequency reached one spike/min neither during intraoperative nor extraoperative recording; therefore appropriate comparison of spike frequency was not possible. A significant positive correlation in the spike-frequency pattern was seen between intraoperative and extraoperative recordings in nine of nine cases who had > or = 10 spikes/min during intraoperative ECoG (mean rho = 0.62; p < 0.01), in five of six cases with one to nine spikes/min (mean rho = 0.50; p < 0.01), and in none of five cases with less than one spike/min (mean rho = 0.13). CONCLUSIONS: General anesthesia often decreases the spike frequency in children with neocortical epilepsy, yet intraoperative ECoG can reliably reflect the awake interictal spiking pattern when spike frequency exceeds one spike/min during intraoperative ECoG recording.     

Spike patterns surrounding sleep and seizures localize the seizure-onset zone in focal epilepsy

Objective

Interictal spikes help localize seizure generators as part of surgical planning for drug-resistant epilepsy. However, there are often multiple spike populations whose frequencies change over time, influenced by brain state. Understanding state changes in spike rates will improve our ability to use spikes for surgical planning. Our goal was to determine the effect of sleep and seizures on interictal spikes, and to use sleep and seizure-related changes in spikes to localize the seizure-onset zone (SOZ).

Methods

We performed a retrospective analysis of intracranial electroencephalography (EEG) data from patients with focal epilepsy. We automatically detected interictal spikes and we classified different time periods as awake or asleep based on the ratio of alpha to delta power, with a secondary analysis using the recently published SleepSEEG algorithm. We analyzed spike rates surrounding sleep and seizures. We developed a model to localize the SOZ using state-dependent spike rates.

Results

We analyzed data from 101 patients (54 women, age range 16–69). The normalized alpha-delta power ratio accurately classified wake from sleep periods (area under the curve = .90). Spikes were more frequent in sleep than wakefulness and in the post-ictal compared to the pre-ictal state. Patients with temporal lobe epilepsy had a greater wake-to-sleep and pre- to post-ictal spike rate increase compared to patients with extra-temporal epilepsy. A machine-learning classifier incorporating state-dependent spike rates accurately identified the SOZ (area under the curve = .83). Spike rates tended to be higher and better localize the seizure-onset zone in non–rapid eye movement (NREM) sleep than in wake or REM sleep.

Significance

The change in spike rates surrounding sleep and seizures differs between temporal and extra-temporal lobe epilepsy. Spikes are more frequent and better localize the SOZ in sleep, particularly in NREM sleep. Quantitative analysis of spikes may provide useful ancillary data to localize the SOZ and improve surgical planning.     

EEG and clinical predictors of medically intractable childhood epilepsy.

OBJECTIVES: To identify electroencephalographic and clinical factors associated with both seizure control and medical intractability in children with epilepsy. METHODS: We retrospectively reviewed EEGs and medical records from children with well-controlled epilepsy or medically intractable epilepsy. SUBJECTS: Features of the initial EEG and clinical findings were compared in 39 children with well controlled seizures and 144 with intractable epilepsy using both univariate and multivariate analyses. RESULTS: Strong univariate associates were noted between intractability and several EEG factors: abnormal EEG background including diffuse slowing, asymmetry, abnormal amplitude, a high frequency of spikes or sharp waves, and focal spike and wave activity. With multiple logistic regression, independent predictors of intractability were diffuse slowing and focal spike and wave activity. Strong univariate associates of clinical factors with intractability included: an early age of onset, simple partial, tonic, and myoclonic seizures, a history of status epilepticus, a symptomatic etiology of the seizures, and abnormal magnetic resonance imaging of the head. Multivariate analysis detected 4 independent clinical features associated with intractable epilepsy: symptomatic etiology, tonic seizures, simple partial seizures, and an early age of onset. CONCLUSIONS: There are a number of EEG and clinical features that can be identified early in the course of childhood epilepsy that are predictive of outcome. These findings will need to be verified in a prospective study.     

Physiologic all-night sleep in patients with severe forms of epilepsy

100 all night sleep records in 90 patients with various forms of epilepsy and 10 patients with syncope were analyzed. There were 10 patients with generalized epilepsy, 41-with partial epilepsy with complex symptomatology and temporal foci, 23--with mixed seizures and frontal focal changes and 16 patients with partial epilepsy with simple seizures and various location of EEG foci. Normal sleep pattern was present in 21% of cases. The most frequent changes of sleep pattern were: prolongation of sleep onset and the latency of the first episode of REM, instability of sleep stages and absence of sleep spindles. Interictal discharges appeared mostly in all sleep stages of NREM. 50% of epileptic patients showed focal spikes in REM. Nocturnal seizures occurred in 18 patients, in several of them very frequently.     

Two magneto-encephalographic epileptic foci did not coincide with the electrocorticographic ictal onset zone in a patient with temporal lobe epilepsy

Abstract

To evaluate the usefulness and limitations of magneto-encephalography (MEG) for epilepsy surgery, we compared 'interictal' epileptic spike fields on MEG with ictal electrocorticography (ECoG) using invasive chronic subdural electrodes in a patient with intractable medial temporal lobe epilepsy (MTLE) associated with vitamin K deficiency intracerebral hemorrhage. A 19-year-old male with an 8-year history of refractory complex partial seizures, secondarily generalized, and right hemispheric atrophy and porencephaly in the right frontal lobe on MRI, was studied with MEG to define the interictal paroxysmal sources based on the single-dipole model. This was followed by invasive ECoG monitoring to delineate the epileptogenic zone. MEG demonstrated two paroxysmal foci, one each on the right lateral temporal and frontal lobes. Ictal ECoG recordings revealed an ictal onset zone on the right medial temporal lobe, which was different from that defined by MEG. Anterior temporal lobectomy with hippocampectomy was performed and the patient has been seizure free for two years. Our results indicate that interictal MEG does not always define the epileptogenic zone in patients with MTLE. [Neurol Res 2001; 23: 830-834]