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P456: Comparison of high gamma electrocorticography and fMRI with electrocortical stimulation for localization of somatosensory and language cortex
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Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
period preceding the fatal seizure, compared with values measured one day and six month before, and also higher than the pre-ictal values in a group of 10 patients with generalised tonic-clonic seizures. This unfortunate case documented during video-EEG monitoring indicates that seizure-induced cardiac dysrhythmia can lead to SUDEP, and suggests that patients with increased parasympathetic activation in the pre-ictal period might have an increased risk of SUDEP in the period following the seizure.
P454 Coincidence of non-convulsive epileptic seizures and stimulation-on phases in a patient with deep brain stimulation of thalamic anterior nuclei I. Bucurenciu 1 , A. Staack 1 , I. Wisniewski 1 , S. Rona 2 , A. Gharabaghi 2 , B.J. Steinhoff 1 1 Epilepsy Center Kork, Kehl-Kork, Germany; 2 University of Tuebingen, Department of Neurosurgery, Tuebingen, Germany Question: Deep brain stimulation (DBS) of the thalamic anterior nuclei (AN) represents a complimentary option for treatment of drug-resistant epilepsies. The putative induction of epileptic seizures by DBS of thalamic AN has been occasionally reported. However, an exact correlation between thalamic stimulation and the electroclinical onset, duration, and semiology of seizures has not been documented until now. Therefore, it is not known whether this side effect occurs as a result of the syndrome and/or protocol. We report the case of a patient with non-lesional epilepsy, who experienced spontaneous and DBS-induced epileptic seizures. In this patient we performed an accurate analysis of the electroclinical effects of thalamic DBS. Methods: A 23 year-old female with non-lesional epilepsy with tonicdyscognitive focal and bilateral convulsive seizures was treated by means of bilateral deep brain stimulation. DBS electrodes were implanted bilaterally in the thalamic anterior nuclei using a stereotactic technique. The following stimulation parameters were used bilaterally and mostly symmetric: amplitudes between 3 and 7.5 V, frequencies between 145 and 180 Hz, pulse widths between 90 and 120 μs, stimulation cycling on/off between 1min/5min and 20s/20s, stimulation plots: 3 and 11 (most lateral located plots). Results: Immediately after initiation of DBS the patient developed almost stupurous mutism. The electroencephalograms (EEGs) showed series of sharp-slow-waves or high amplitude theta-delta discharges that regularly occurred during the on-phases of a stimulation cycle and correlated well with fluctuating neurocognitive impairments. In a long-term EEG recording, regularly occurring periods of sharp-slow-waves or slow-wave discharges, coincident to the thalamic stimulation were also documented. Neuropsychological assessment performed at the end of a stimulation-free period of several months and three days after restarting the thalamic stimulation showed an abrupt impairment of attention and executive functions. Conclusion: In difficult-to-treat epilepsy patients, DBS of the anterior thalamus may occasionally induce electroclinical worsening.
P455 Enhanced ictal and interictal gamma coherence in children with idiopathic generalised epilepsy K. Benedek 1 , A. Berényi 2 , P. Gombkoeto˝ 2 , H. Piilgaard Hansen 1 , M. Lauritzen 1,3 1 Glostrup Hospital, Clinical Neurophysiology, Glostrup, Denmark; 2 University of Szeged, Department of Physiology, Szeged, Hungary; 3 University of Copenhagen, Deparment of Neuroscience and Pharmacology, Copenhagen, Denmark Background and aim: Cortico-thalamo-cortical circuits play a crucial role in generating oscillations in various frequency bands in association with idiopathic generalized epilepsy (IGE). We here tested the hypothesis that cortical rhythmic EEG activity in the gamma band (40-80 Hz) coincided with and possibly caused spike-wave-discharges (SWD) in patients with idiopathic generalised epilepsy (IGE). Method: Ictal and interictal EEG recordings of 14 children with IGE (mean age 8.5±5 years) and age and sex matched controls were evaluated. Network operator functions of high frequency synchronization were assessed in IGE patients during interictal and ictal states with respect to cortical coherence to evaluate cortico-cortical connectivity. Power spectrum density and intra- and inter-hemispheric coherence profiles were estimated using a block autoregressive parametric model.
Results: In the interictal state IGE patients displayed significantly larger number of coherence peaks in the gamma range as compared to controls (p<0.001). The highest peaks were in central and fronto-central regions. The ictal state was characterized by absences and SWD that coincided with coalescence of activity in all EEG frequency bands including the gamma band, i.e. slow and fast oscillatory activities grouped in the ictal state. Conclusions: IGE patients showed abnormal EEG hypersynchrony in the gamma range compared to control patients in the interictal state with preponderance in frontal and frontocentral regions. Different brain rhythms, with both low- and fast-frequency activities, were grouped within complex wave-sequences during SWD associated with absence seizures. Thus, SWD are characterized by coalescence of high and low frequency bands at high power and not one or a few slow frequencies associated with a spike as it is commonly believed.
P456 Comparison of high gamma electrocorticography and fMRI with electrocortical stimulation for localization of somatosensory and language cortex M. Genetti 1 , R. Tyrand 1 , F. Grouiller 2 , A. Lascano 1 , S. Vulliemoz 1 , L. Spinelli 1 , K. Schaller 3 , M. Seeck 1 , C. Michel 1 1 Geneva University Hospitals, Clinical neuroscience and neurology, Geneva, Switzerland; 2 Geneva University Hospitals, Radiology, Geneva, Switzerland; 3 Geneva University Hospitals, Neurosurgery, Geneva, Switzerland Question: In patients with pharmacoresistant epilepsy, electrocortical stimulation (ECS) has been established as the gold-standard for pre-surgical mapping. Yet, ECS is not suitable for all patients due to lengthy sessions and imperfect collaboration. To overstep the limitations of ECS, we investigate the contribution of time-frequency analysis of electrocorticography (ECoG) and functional magnetic resonance imaging (fMRI) for the localization of primary (somatosensory) and associate (language) cortices. Methods: 23 consecutive patients with subdural electrodes underwent a somatosensory stimulation protocol and/or an auditory semantic decision task. Fourteen patients did the same protocol with fMRI before implantation. We compared functional mapping by induced high gamma (hg) ECoG activity (70-160 Hz) and by fMRI with that suggested by ECS and with respect to the postoperative outcome. Results: ECS resulted in the identification of somatosensory area sites of the thumb in 12/16 patients. HgECoG revealed somatosensory cortex in all these patients, overlapping with 67% of the positive ECS electrodes (true positive). Positive hgECoG responses were found in 4% of the negative ECS electrodes (false positive). In 3 ECS non responsive patients, hgECoG identified 12 electrodes presumably corresponding to somatosensory cortex. FMRI responses showed 33% of true positive and 5% of false positive electrodes. Language-related sites were identified with ECS in 7/12 patients. In all 7 patients, hgECoG responses demonstrated 50% of true positive and 8% of false positive electrodes. FMRI responses revealed 64% of true positive but 23% of false positive electrodes. Nevertheless, in 3 patients who developed post-surgical language deficits, hgECoG and fMRI sites were inside the resection, consistent with ECS. Moreover, in one patient who suffered from post-surgical language impairments, the resection included hgECoG positive sites that ECS failed to detect. Conclusions: HgECoG and fMRI are useful tools for pre-surgical mapping and provide additional localization information in patients who cannot sufficiently collaborate for extra-operative ECS sessions. However, hgECoG is significantly more specific than fMRI to identify primary and associate cortical areas.
P458 HMGA2 gene allele variants are associated with EEG interictal epileptiform activity in temporal lobe epilepsy J.A. Bragatti, I.C. Bandeira, A.M. Carvalho, P.A. Cherubini, C.M. Torres, S.L. Segal, M.M. Bianchin Hospital de Clinicas de Porto Alegre, Neurology, Porto Alegre, RS, Brazil Introduction: EEG interictal epileptiform discharges are a hallmark of epilepsy, and they are considered a biomarker for localization of the epileptogenic area, besides to be implicated in disease severity, and in prognosis after a first seizure and after epilepsy surgery. They are influenced by several factors, like dipole localization and orientation, sleep-wake cycle and CNS active drugs. Few authors have studied the influence of genetic
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
period preceding the fatal seizure, compared with values measured one day and six month before, and also higher than the pre-ictal values in a group of 10 patients with generalised tonic-clonic seizures. This unfortunate case documented during video-EEG monitoring indicates that seizure-induced cardiac dysrhythmia can lead to SUDEP, and suggests that patients with increased parasympathetic activation in the pre-ictal period might have an increased risk of SUDEP in the period following the seizure.
P454 Coincidence of non-convulsive epileptic seizures and stimulation-on phases in a patient with deep brain stimulation of thalamic anterior nuclei I. Bucurenciu 1 , A. Staack 1 , I. Wisniewski 1 , S. Rona 2 , A. Gharabaghi 2 , B.J. Steinhoff 1 1 Epilepsy Center Kork, Kehl-Kork, Germany; 2 University of Tuebingen, Department of Neurosurgery, Tuebingen, Germany Question: Deep brain stimulation (DBS) of the thalamic anterior nuclei (AN) represents a complimentary option for treatment of drug-resistant epilepsies. The putative induction of epileptic seizures by DBS of thalamic AN has been occasionally reported. However, an exact correlation between thalamic stimulation and the electroclinical onset, duration, and semiology of seizures has not been documented until now. Therefore, it is not known whether this side effect occurs as a result of the syndrome and/or protocol. We report the case of a patient with non-lesional epilepsy, who experienced spontaneous and DBS-induced epileptic seizures. In this patient we performed an accurate analysis of the electroclinical effects of thalamic DBS. Methods: A 23 year-old female with non-lesional epilepsy with tonicdyscognitive focal and bilateral convulsive seizures was treated by means of bilateral deep brain stimulation. DBS electrodes were implanted bilaterally in the thalamic anterior nuclei using a stereotactic technique. The following stimulation parameters were used bilaterally and mostly symmetric: amplitudes between 3 and 7.5 V, frequencies between 145 and 180 Hz, pulse widths between 90 and 120 μs, stimulation cycling on/off between 1min/5min and 20s/20s, stimulation plots: 3 and 11 (most lateral located plots). Results: Immediately after initiation of DBS the patient developed almost stupurous mutism. The electroencephalograms (EEGs) showed series of sharp-slow-waves or high amplitude theta-delta discharges that regularly occurred during the on-phases of a stimulation cycle and correlated well with fluctuating neurocognitive impairments. In a long-term EEG recording, regularly occurring periods of sharp-slow-waves or slow-wave discharges, coincident to the thalamic stimulation were also documented. Neuropsychological assessment performed at the end of a stimulation-free period of several months and three days after restarting the thalamic stimulation showed an abrupt impairment of attention and executive functions. Conclusion: In difficult-to-treat epilepsy patients, DBS of the anterior thalamus may occasionally induce electroclinical worsening.
P455 Enhanced ictal and interictal gamma coherence in children with idiopathic generalised epilepsy K. Benedek 1 , A. Berényi 2 , P. Gombkoeto˝ 2 , H. Piilgaard Hansen 1 , M. Lauritzen 1,3 1 Glostrup Hospital, Clinical Neurophysiology, Glostrup, Denmark; 2 University of Szeged, Department of Physiology, Szeged, Hungary; 3 University of Copenhagen, Deparment of Neuroscience and Pharmacology, Copenhagen, Denmark Background and aim: Cortico-thalamo-cortical circuits play a crucial role in generating oscillations in various frequency bands in association with idiopathic generalized epilepsy (IGE). We here tested the hypothesis that cortical rhythmic EEG activity in the gamma band (40-80 Hz) coincided with and possibly caused spike-wave-discharges (SWD) in patients with idiopathic generalised epilepsy (IGE). Method: Ictal and interictal EEG recordings of 14 children with IGE (mean age 8.5±5 years) and age and sex matched controls were evaluated. Network operator functions of high frequency synchronization were assessed in IGE patients during interictal and ictal states with respect to cortical coherence to evaluate cortico-cortical connectivity. Power spectrum density and intra- and inter-hemispheric coherence profiles were estimated using a block autoregressive parametric model.
Results: In the interictal state IGE patients displayed significantly larger number of coherence peaks in the gamma range as compared to controls (p<0.001). The highest peaks were in central and fronto-central regions. The ictal state was characterized by absences and SWD that coincided with coalescence of activity in all EEG frequency bands including the gamma band, i.e. slow and fast oscillatory activities grouped in the ictal state. Conclusions: IGE patients showed abnormal EEG hypersynchrony in the gamma range compared to control patients in the interictal state with preponderance in frontal and frontocentral regions. Different brain rhythms, with both low- and fast-frequency activities, were grouped within complex wave-sequences during SWD associated with absence seizures. Thus, SWD are characterized by coalescence of high and low frequency bands at high power and not one or a few slow frequencies associated with a spike as it is commonly believed.
P456 Comparison of high gamma electrocorticography and fMRI with electrocortical stimulation for localization of somatosensory and language cortex M. Genetti 1 , R. Tyrand 1 , F. Grouiller 2 , A. Lascano 1 , S. Vulliemoz 1 , L. Spinelli 1 , K. Schaller 3 , M. Seeck 1 , C. Michel 1 1 Geneva University Hospitals, Clinical neuroscience and neurology, Geneva, Switzerland; 2 Geneva University Hospitals, Radiology, Geneva, Switzerland; 3 Geneva University Hospitals, Neurosurgery, Geneva, Switzerland Question: In patients with pharmacoresistant epilepsy, electrocortical stimulation (ECS) has been established as the gold-standard for pre-surgical mapping. Yet, ECS is not suitable for all patients due to lengthy sessions and imperfect collaboration. To overstep the limitations of ECS, we investigate the contribution of time-frequency analysis of electrocorticography (ECoG) and functional magnetic resonance imaging (fMRI) for the localization of primary (somatosensory) and associate (language) cortices. Methods: 23 consecutive patients with subdural electrodes underwent a somatosensory stimulation protocol and/or an auditory semantic decision task. Fourteen patients did the same protocol with fMRI before implantation. We compared functional mapping by induced high gamma (hg) ECoG activity (70-160 Hz) and by fMRI with that suggested by ECS and with respect to the postoperative outcome. Results: ECS resulted in the identification of somatosensory area sites of the thumb in 12/16 patients. HgECoG revealed somatosensory cortex in all these patients, overlapping with 67% of the positive ECS electrodes (true positive). Positive hgECoG responses were found in 4% of the negative ECS electrodes (false positive). In 3 ECS non responsive patients, hgECoG identified 12 electrodes presumably corresponding to somatosensory cortex. FMRI responses showed 33% of true positive and 5% of false positive electrodes. Language-related sites were identified with ECS in 7/12 patients. In all 7 patients, hgECoG responses demonstrated 50% of true positive and 8% of false positive electrodes. FMRI responses revealed 64% of true positive but 23% of false positive electrodes. Nevertheless, in 3 patients who developed post-surgical language deficits, hgECoG and fMRI sites were inside the resection, consistent with ECS. Moreover, in one patient who suffered from post-surgical language impairments, the resection included hgECoG positive sites that ECS failed to detect. Conclusions: HgECoG and fMRI are useful tools for pre-surgical mapping and provide additional localization information in patients who cannot sufficiently collaborate for extra-operative ECS sessions. However, hgECoG is significantly more specific than fMRI to identify primary and associate cortical areas.
P458 HMGA2 gene allele variants are associated with EEG interictal epileptiform activity in temporal lobe epilepsy J.A. Bragatti, I.C. Bandeira, A.M. Carvalho, P.A. Cherubini, C.M. Torres, S.L. Segal, M.M. Bianchin Hospital de Clinicas de Porto Alegre, Neurology, Porto Alegre, RS, Brazil Introduction: EEG interictal epileptiform discharges are a hallmark of epilepsy, and they are considered a biomarker for localization of the epileptogenic area, besides to be implicated in disease severity, and in prognosis after a first seizure and after epilepsy surgery. They are influenced by several factors, like dipole localization and orientation, sleep-wake cycle and CNS active drugs. Few authors have studied the influence of genetic