Neocortical Epilepsy (neocortical + epilepsy)

Distribution by Scientific Domains


Selected Abstracts


Dynamic Changes of Ictal High-Frequency Oscillations in Neocortical Epilepsy: Using Multiple Band Frequency Analysis

EPILEPSIA, Issue 2 2007
Ayako Ochi
Summary:,Purpose: To characterize the spatial and temporal course of ictal high-frequency oscillations (HFOs) recorded by subdural EEG in children with intractable neocortical epilepsy. Methods: We retrospectively studied nine children (four girls, five boys; 4,17 yr) who presented with intractable extrahippocampal localization-related epilepsy and who underwent extraoperative video subdural EEG (1000 Hz sampling rate) and cortical resection. We performed multiple band frequency analysis (MBFA) to evaluate the frequency, time course, and distribution of ictal HFOs. We compared ictal HFO changes before and after clinical onset and postsurgical seizure outcomes. Results: Seventy-eight of 79 seizures showed HFOs. We observed wide-band HFOs (,250Hz, ,120 electrodes) in six patients either with partial seizures alone (three patients) or with epileptic spasms (three patients). Three patients with partial seizures that secondarily generalized had wide-band HFOs (,170 Hz) before clinical onset and sustained narrow-band HFOs (60,164 Hz) with electrodecremental events after clinical onset (,28 electrodes). In four postoperatively seizure-free patients, more electrodes recorded higher-frequency HFOs inside the resection area than outside before and after clinical seizure onset. In five patients with residual seizures, electrodes recorded more HFOs that were of higher or equal frequency outside the surgical area than inside after clinical onset. Conclusion: For partial seizures alone and epileptic spasms, more electrodes recorded only wide-band HFOs; for partial seizures that secondarily generalized, fewer electrodes recorded wide-band HFOs, but in these seizures electrodes also recorded subsequent sustained narrow-band ictal HFOs. Resection of those brain regions having electrodes with ictal, higher HFOs resulted in postsurgical seizure-free outcomes. [source]


Characterization of the Tetanus Toxin Model of Refractory Focal Neocortical Epilepsy in the Rat

EPILEPSIA, Issue 2 2005
Karen E. Nilsen
Summary:,Purpose: To characterize in detail a model of focal neocortical epilepsy. Methods: Chronic focal epilepsy was induced by injecting 25,50 ng of tetanus toxin or vehicle alone (controls) into the motor neocortex of rats. EEG activity was recorded from electrodes implanted at the injection site, along with facial muscle electromyographic (EMG) activity and behavioral monitoring intermittently for up to 5 months in some animals. Drug responsiveness was assessed by using the antiepileptic drugs (AEDs) diazepam (DZP) and phenytoin (PHT) delivered systemically, while 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), a competitive antagonist at AMPA receptors, was administered directly to the brain to investigate the potential benefits of focal drug delivery. Results: Tetanus toxin induced mild behavioral seizures that persisted indefinitely in all animals. EEG spiking activity, occurring up to 80% of the time, correlated with clinical seizures consisting of interrupted behavioral activity, rhythmic bilateral facial twitching, and periods of abrupt motor arrest. Seizures were refractory to systemic administration of DZP and PHT. However, focal delivery of NBQX to the seizure site reversibly reduced EEG and behavioral seizure activity without detectable side effects. Conclusions: This study provides a long-term detailed characterisation of the tetanus toxin model. Spontaneous, almost continuous, well-tolerated seizures occur and persist, resembling those seen in neocortical epilepsy, including cortical myoclonus and epilepsia partialis continua. The seizures appear to be similarly resistant to conventional AEDs. The consistency, frequency, and clinical similarity of the seizures to refractory epilepsy in humans make this an ideal model for investigation of both mechanisms of seizure activity and new therapeutic approaches. [source]


Increased Expression of the Neuronal Glutamate Transporter (EAAT3/EAAC1) in Hippocampal and Neocortical Epilepsy

EPILEPSIA, Issue 3 2002
Peter B. Crino
Summary: ,Purpose: To define the changes in gene and protein expression of the neuronal glutamate transporter (EAAT3/EAAC1) in a rat model of temporal lobe epilepsy as well as in human hippocampal and neocortical epilepsy. Methods: The expression of EAAT3/EAAC1 mRNA was measured by reverse Northern blotting in single dissociated hippocampal dentate granule cells from rats with pilocarpine-induced temporal lobe epilepsy (TLE) and age-matched controls, in dentate granule cells from hippocampal surgical specimens from patients with TLE, and in dysplastic neurons microdissected from human focal cortical dysplasia specimens. Immunolabeling of rat and human hippocampi and cortical dysplasia tissue with EAAT3/EAAC1 antibodies served to corroborate the mRNA expression analysis. Results: The expression of EAAT3/EAAC1 mRNA was increased by nearly threefold in dentate granule cells from rats with spontaneous seizures compared with dentate granule cells from control rats. EAAT3/EAAC1 mRNA levels also were high in human dentate granule cells from patients with TLE and were significantly elevated in dysplastic neurons in cortical dysplasia compared with nondysplastic neurons from postmortem control tissue. No difference in expression of another glutamate transporter, EAAT2/GLT-1, was observed. Immunolabeling demonstrated that EAAT3/EAAC1 protein expression was enhanced in dentate granule cells from both rats and humans with TLE as well as in dysplastic neurons from human cortical dysplasia tissue. Conclusions: Elevations of EAAT3/EAAC1 mRNA and protein levels are present in neurons from hippocampus and neocortex in both rats and humans with epilepsy. Upregulation of EAAT3/EAAC1 in hippocampal and neocortical epilepsy may be an important modulator of extracellular glutamate concentrations and may occur as a response to recurrent seizures in these cell types. [source]


Ictal Brain Hyperperfusion Contralateral to Seizure Onset: The SPECT Mirror Image

EPILEPSIA, Issue 1 2006
Gilles Huberfeld
Summary:,Purpose: Ictal single-photon emission computed tomography (SPECT) may help localize the seizure-onset zone (SOZ) by detecting changes in regional cerebral blood flow induced by epileptic discharges. This imaging method also reveals hyperperfusions in areas of seizure propagation, including the hemisphere contralateral to the SOZ. We have studied the occurrence, the topography, and the clinical value of such contralateral ictal hyperperfusion areas (HPAs). Methods: We examined data from presurgical evaluations of 36 consecutive patients with pharmacoresistant partial epilepsy of various localizations. Ictal and interictal SPECT examinations were made with 99mTc-ECD, and the scans were processed for coregistration, normalization, subtraction, and merging with MRI images. Results: Contralateral HPAs were observed in 72% of the patients: 50% of mesiotemporal epilepsy cases with hippocampal sclerosis, 85.7% of the other mesiotemporal epilepsies, 85.7% of neocortical lateral temporal epilepsies, and 87.5% of extratemporal epilepsies. Contralateral HPAs were usually symmetrical to the SOZ, forming a mirror image, observed in 57.1% of the patients. They could be slightly asymmetrical in mesiotemporal epilepsies, perhaps because of the particular anatomic pathways linking temporal lobes. In neocortical epilepsies, they were located in the cortex homotopic to the SOZ. Conclusions: We show that the symmetrical nature of the mirror image usually does not disturb SPECT interpretation. It can confirm the location of the SOZ (11 patients) and even occasionally improve the precision of its definition (nine patients) by restraining several potential SOZ-related HPAs to a single one or by permitting a restricted localization of the SOZ in a large HPA. [source]


Functional MRI Predicts Memory Performance after Right Mesiotemporal Epilepsy Surgery

EPILEPSIA, Issue 2 2005
Jozsef Janszky
Summary:,Purpose: Anterior temporal lobe resection (ATR) is a treatment option in drug-resistant epilepsy. An important risk of ATR is loss of memory because mesiotemporal structures contribute substantially to memory function. We investigated whether memory-activated functional MRI (fMRI) can predict postoperative memory loss after anterior temporal lobectomy in right-sided medial temporal lobe epilepsy (MTLE). Methods: We included 16 patients (10 women) aged 16,54 years. The mean age at epilepsy onset was 12.5 years (range, 1,26 years). The patients' mean Wechsler IQ score was 95.2 (range, 62,125). The activation condition of fMRI consisted of retrieval from long-term memory induced by self-paced performance of an imaginative walk. All but one patient had left-sided speech dominance according to speech-activated fMRI. Outside the scanner, we evaluated the pre- and postoperative visual memory retention by using Rey Visual Design Learning Test. Results: We found a correlation between the preoperative asymmetry index of memory- fMRI and the change between pre- and postsurgical measures of memory retention. Reduced activation of the mesiotemporal region ipsilateral to the epileptogenic region correlated with a favorable memory outcome after right-sided ATR. Conclusions: In light of the postoperative results, the theoretical implication of our study is that fMRI based on a simple introspective retrieval task measures memory functions. The main clinical implication of our study is that memory- fMRI might replace the invasive Wada test in MTLE by using a simple fMRI paradigm. Predictive power, however, will be studied in larger patient samples. Other studies are required for left-sided MTLE and neocortical epilepsies to assess the clinical usefulness of memory- fMRI. [source]


Calcium imaging of epileptiform events with single-cell resolution

DEVELOPMENTAL NEUROBIOLOGY, Issue 3 2001
Tudor Badea
Abstract Epileptic discharges propagate through apparently normal circuits, although it is still unclear how this recruitment takes place. To understand the role of different classes of neurons in neocortical epilepsy, we have developed a novel imaging assay that detects which neurons participate in epileptiform discharges. Using calcium imaging of neuronal populations during bicuculline-induced spontaneous epileptiform events in slices from juvenile mouse somatosensory cortex, we find that fast calcium transients correlate with epileptiform field potentials and intracellular depolarizing shifts and can be used as an optical signature that a given neuron has participated in an epileptiform event. Our results demonstrate a novel method to characterize epileptiform events with single-cell resolution. In addition, our data are consistent with an important role for layer 5 in generating neocortical seizures and indicate that subgroups of neurons are particularly prone to epileptiform recruitment. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 215,227, 2001 [source]


Dynamic Changes of Ictal High-Frequency Oscillations in Neocortical Epilepsy: Using Multiple Band Frequency Analysis

EPILEPSIA, Issue 2 2007
Ayako Ochi
Summary:,Purpose: To characterize the spatial and temporal course of ictal high-frequency oscillations (HFOs) recorded by subdural EEG in children with intractable neocortical epilepsy. Methods: We retrospectively studied nine children (four girls, five boys; 4,17 yr) who presented with intractable extrahippocampal localization-related epilepsy and who underwent extraoperative video subdural EEG (1000 Hz sampling rate) and cortical resection. We performed multiple band frequency analysis (MBFA) to evaluate the frequency, time course, and distribution of ictal HFOs. We compared ictal HFO changes before and after clinical onset and postsurgical seizure outcomes. Results: Seventy-eight of 79 seizures showed HFOs. We observed wide-band HFOs (,250Hz, ,120 electrodes) in six patients either with partial seizures alone (three patients) or with epileptic spasms (three patients). Three patients with partial seizures that secondarily generalized had wide-band HFOs (,170 Hz) before clinical onset and sustained narrow-band HFOs (60,164 Hz) with electrodecremental events after clinical onset (,28 electrodes). In four postoperatively seizure-free patients, more electrodes recorded higher-frequency HFOs inside the resection area than outside before and after clinical seizure onset. In five patients with residual seizures, electrodes recorded more HFOs that were of higher or equal frequency outside the surgical area than inside after clinical onset. Conclusion: For partial seizures alone and epileptic spasms, more electrodes recorded only wide-band HFOs; for partial seizures that secondarily generalized, fewer electrodes recorded wide-band HFOs, but in these seizures electrodes also recorded subsequent sustained narrow-band ictal HFOs. Resection of those brain regions having electrodes with ictal, higher HFOs resulted in postsurgical seizure-free outcomes. [source]


Characterization of the Tetanus Toxin Model of Refractory Focal Neocortical Epilepsy in the Rat

EPILEPSIA, Issue 2 2005
Karen E. Nilsen
Summary:,Purpose: To characterize in detail a model of focal neocortical epilepsy. Methods: Chronic focal epilepsy was induced by injecting 25,50 ng of tetanus toxin or vehicle alone (controls) into the motor neocortex of rats. EEG activity was recorded from electrodes implanted at the injection site, along with facial muscle electromyographic (EMG) activity and behavioral monitoring intermittently for up to 5 months in some animals. Drug responsiveness was assessed by using the antiepileptic drugs (AEDs) diazepam (DZP) and phenytoin (PHT) delivered systemically, while 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), a competitive antagonist at AMPA receptors, was administered directly to the brain to investigate the potential benefits of focal drug delivery. Results: Tetanus toxin induced mild behavioral seizures that persisted indefinitely in all animals. EEG spiking activity, occurring up to 80% of the time, correlated with clinical seizures consisting of interrupted behavioral activity, rhythmic bilateral facial twitching, and periods of abrupt motor arrest. Seizures were refractory to systemic administration of DZP and PHT. However, focal delivery of NBQX to the seizure site reversibly reduced EEG and behavioral seizure activity without detectable side effects. Conclusions: This study provides a long-term detailed characterisation of the tetanus toxin model. Spontaneous, almost continuous, well-tolerated seizures occur and persist, resembling those seen in neocortical epilepsy, including cortical myoclonus and epilepsia partialis continua. The seizures appear to be similarly resistant to conventional AEDs. The consistency, frequency, and clinical similarity of the seizures to refractory epilepsy in humans make this an ideal model for investigation of both mechanisms of seizure activity and new therapeutic approaches. [source]


Increased Expression of the Neuronal Glutamate Transporter (EAAT3/EAAC1) in Hippocampal and Neocortical Epilepsy

EPILEPSIA, Issue 3 2002
Peter B. Crino
Summary: ,Purpose: To define the changes in gene and protein expression of the neuronal glutamate transporter (EAAT3/EAAC1) in a rat model of temporal lobe epilepsy as well as in human hippocampal and neocortical epilepsy. Methods: The expression of EAAT3/EAAC1 mRNA was measured by reverse Northern blotting in single dissociated hippocampal dentate granule cells from rats with pilocarpine-induced temporal lobe epilepsy (TLE) and age-matched controls, in dentate granule cells from hippocampal surgical specimens from patients with TLE, and in dysplastic neurons microdissected from human focal cortical dysplasia specimens. Immunolabeling of rat and human hippocampi and cortical dysplasia tissue with EAAT3/EAAC1 antibodies served to corroborate the mRNA expression analysis. Results: The expression of EAAT3/EAAC1 mRNA was increased by nearly threefold in dentate granule cells from rats with spontaneous seizures compared with dentate granule cells from control rats. EAAT3/EAAC1 mRNA levels also were high in human dentate granule cells from patients with TLE and were significantly elevated in dysplastic neurons in cortical dysplasia compared with nondysplastic neurons from postmortem control tissue. No difference in expression of another glutamate transporter, EAAT2/GLT-1, was observed. Immunolabeling demonstrated that EAAT3/EAAC1 protein expression was enhanced in dentate granule cells from both rats and humans with TLE as well as in dysplastic neurons from human cortical dysplasia tissue. Conclusions: Elevations of EAAT3/EAAC1 mRNA and protein levels are present in neurons from hippocampus and neocortex in both rats and humans with epilepsy. Upregulation of EAAT3/EAAC1 in hippocampal and neocortical epilepsy may be an important modulator of extracellular glutamate concentrations and may occur as a response to recurrent seizures in these cell types. [source]


Neuronal Disconnection for the Surgical Treatment of Pediatric Epilepsy

EPILEPSIA, Issue 2000
Hiroyuki Shimizu
Summary: The surgical methods and results of disconnective surgery for pediatric epilepsy were retrospectively analyzed. The techniques of neuronal disconnection included multiple subpial resection (MST), corpus callosotomy, and functional hemisphercctomy by disconnection. Of 158 total pediatric operations, disconnective techniques were employed in more than 60% of the cases. MST was applied when the epileptic focus was located in unresectable cortices such as speech or motor areas. MST was also instrumental when the epileptogenic zone was extensive and was widely disseminated, as is often observed in cases of neocortical epilepsy. Of 25 patients who underwent MST, surgical outcomes after > 1 year follow-up showed Engel Class I or II in 10 cases, Class III in 12, and Class IV in 3. No mortality or morbidity was encountered during surgery or postoperatively. Corpus callosotomy was applied to cases of disabling generalized seizures and showed a marked effect in alleviating potentially injurious drop attacks. Of 34 patients with drop attacks, 29 became free from this type of seizure, 4 had infrequent attacks, and only 1 showed no beneficial effect. Postoperative improvement of cognition and speech was recognized in 77% of the cases. We developed a new method of functional hemispherectomy by fiber disconnection and applied this less invasive technique to 23 cases of hemispheric lesions. Of the 17 cases with > 1 year follow-up, 13 were in Class I or II, and 3 in Class III, and 2 in Class IV. Development partially normalized in infants with good seizure outcomes. [source]


Withdrawal of antiepileptic drugs after neocortical epilepsy surgery

ANNALS OF NEUROLOGY, Issue 2 2010
Kyung-Il Park MD
Objective This study investigated the prevalence of successful antiepileptic drug withdrawal and identified predictors of seizure recurrence after antiepileptic drug reduction following resectional operation for intractable neocortical epilepsy. Methods We retrospectively assessed 223 patients (100 with neocortical temporal lobe epilepsy, 69 with frontal lobe epilepsy, 23 with parietal lobe epilepsy, 25 with occipital lobe epilepsy, and 6 with multifocal epilepsy) who underwent surgery. The mean period of observation was 84.4 months (range, 24,152 months) after surgery and 72.6 months (range, 12,138 months) after initial reduction. Clinical characteristics, magnetic resonance imaging, and surgical parameters were evaluated for their potential to predict recurrence associated with antiepileptic drug withdrawal. Results Antiepileptic drug reduction was attempted in 147 patients (65.9%), 78 (53.1%) of whom had seizure recurrence after initial reduction. Discontinuation was achieved in 73 patients (32.7%), and 59 (80.8%) of these remained seizure free until final assessment. Multivariate analysis revealed that early drug tapering, normal magnetic resonance imaging results, seizure before reduction, and longer epilepsy duration were associated with recurrence. Finally, 27.4% of patients were seizure free without drugs, and 26.9% were seizure free with drugs. Compared with preoperative status, the number of antiepileptic drugs needed decreased in 50.7% of patients, did not change in 19.3%, and increased in 30.0% after surgery. Interpretation The complete-cure rate of intractable neocortical epilepsy by resectional surgery was 27.4%. When patients undertake early tapering, and have normal magnetic resonance imaging results, seizure before reduction, and longer disease duration, further withdrawal should be done cautiously because of the high risk of relapse. ANN NEUROL 2010;67:230,238 [source]