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3. Dynamic effective connectivity of epileptic networks determined with high density EEG source analysis
Society Proceedings / Clinical Neurophysiology 123 (2012) e101–e114
3. Dynamic effective connectivity of epileptic networks determined with high density EEG source analysis—G. Plomp d, R. Tyrand d, L. Astolfi b, B. He c, M. Seeck a, C.M. Michel d, S. Vulliemoz a (a Neurology – HUG, Geneva, Switzerland, b Sapienza University, Roma, Italy, c University of Minnesota, Minneapolis, Switzerland, d Faculty of Medicine, Geneva, Switzerland) Introduction: Analyzing the dynamic behaviour of epileptic networks could help to better understand the way pathologic neural activity propagates, and leads to spikes, seizures, and their electroclinical and cognitive manifestations, with implications for epilepsy surgery candidates. Methods: In 6 patients with temporal lobe epilepsy we studied effective connectivity of large-scale cortical networks at high temporal resolution around interictal spikes, recorded with high density (256 channels) EEG. The cortical electric source activity was obtained for 90 cortical regions of interest (ROI) using a distributed inverse solution. Multivariate, time-varying (millisecond resolution), and frequency-resolved (1–50 Hz) Granger causality analysis (Partial Directed Coherence) was applied to the source signal for all ROIs. In all patients subsequent intracranial recording or surgical resection was used for validation. Results: Information flow occurred predominantly in the theta and beta bands. The key driving structures where located in the anterior and medial temporal regions, with peak information transfer before the spike maximum. We found fast-varying connectivity patterns between the antero-medial and lateral temporal lobe and basal frontal lobe, but also transient transfer towards the contralateral temporal lobe. In two patients with a multifocal irritative zone, we found evidence of connectivity from the main anterior temporal driver towards the secondary spike focus remote from the epileptogenic zone. Conclusion: EEG-based time-varying effective connectivity of epileptic spikes provides a clear characterization of the epileptic networks that is concordant with invasive electro-clinical findings. This could have major clinical implications for tailoring resective, disconnective, and functional surgery. doi:10.1016/j.clinph.2012.03.067
4. Cerebral embolism in endarterectomy versus stenting for symptomatic carotid artery stenosis: The significance of plaque morphology on duplex ultrasound—A.B. Burow, P.L. Lyrer, M.A. Amort, P.J.N. Nederkoorn, M.M.B. Brown, R.S. Sztajzel, S.E. Engelter, L.H.B. Bonati (Queen Square National Hospital, London, United Kingdom, Academic Medical Center, Amsterdam, The Netherlands) Background: Carotid stenting (CAS) and carotid endarterectomy (CEA) may be complicated by cerebral embolism which often remains clinically silent. Unstable carotid plaques might increase the risk for peri-procedural embolism. We studied whether quantitative assessment of carotid plaque echogenity on ultrasound predicts the risk of cerebral ischaemia during CAS or CEA. Methods: In 50 consecutive patients with symptomatic carotid stenosis randomised to CAS (n = 26) or CEA (n = 24) in the International Carotid Stenting Study, semi-automated grey scale measurement of baseline carotid ultrasound images was performed. Greyscale median, percentage of plaque area <20th percentile of greyscale values, and an echographic risk index based on degree of stenosis and plaque area below the 20th percentile of grey-scale values were determined, both for the entire plaque and plaque surface. Brain MRI including diffusion-weighted imaging (DWI) was per-
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formed within 7 days before and 3 days after treatment as part of the ICSS–MRI substudy. The primary outcome on MRI was the presence of at least 1 new hyperintense DWI lesion after treatment. Results: In the CAS group, patients with new DWI lesions after treatment (n = 18) had significantly higher whole-plaque echographic risk indices at baseline (mean 0.1050) than patients without new lesions (n = 8; mean 0.0263; p = 0.012). GSM was 26.7 for patients with and 34.3 for patients without lesions (p = 0.163). Other measures of plaque echogenity did not differ significantly. In the CEA group, there were no significant differences in plaque echogenity measures between patients with (n = 2) and those without DWI lesions (n = 23). Conclusion: Our results show that among patients treated with CAS, the echographic risk index was higher in patients with new ischaemic brain lesions after treatment than in those without new lesions. Quantitative ultrasound plaque analysis may be helpful in estimating the risk of embolic complications in CAS. doi:10.1016/j.clinph.2012.03.068
5. Seizure control after epilepsy surgery: Experience in young children and adolescents—B. Jenny a, Y. El Hassani a, S. Momjian a, C. Pollo b, M. Seeck a, K. Schaller a (a Hôpitaux Universitaires de Genève (HUGs), Geneva, Switzerland, b Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland) Introduction: Surgery for pharmacoresistant epilepsy is well accepted as an efficient treatment for children suffering the debilitating consequences of repetitive seizures. The goal of this study was to analyse seizure control and complications after epilepsy surgery in our center. Methods: Data were retrospectively reviewed from 73 patients aged from 5 months to 16 years old who underwent epilepsy surgery at the Geneva University Hospital and Lausanne University Hospital between 1997 and 2011. Epilepsy surgery included temporal surgery (29 cases), extra-temporal surgery (32 cases) and hemispherotomies (12 cases). Three aged groups were identified: under 3 years old (18 cases), between 4 and 12 years old (35 cases) and between 13 and 17 years old (20 cases). Mean follow-up was 27.25 months (range 4–96 months). Results: The overall seizure-free rate at the time of follow up was 65.7% (48 out of 73 cases). Interestingly in children under 3 years old, the seizure free rate after surgery was 83.3% (15 out of 18 cases). Also, the seizure free outcome was significantly better for temporal epilepsy (79.3%) compared to extra-temporal epilepsy (56.2%) (p = 0.028, < 0.05). At least 50.6% of patients (37 out of 73 cases) had a reduction in their post-operative antiepileptic medication. Complications included five transient hemiparesis, two wound infections, one cerebral oedema after hemispherotomy, one extradural hematoma, one subdural hematoma after insertion of subdural grids and one intraventricular hematoma after hemispherotomy. Conclusions: These data highlight the good outcome and significant seizure free rate of epilepsy surgery at a very young age (children under 3 y/o). Efforts to promote epilepsy surgery in children are crucial since it significantly impacts on the cognitive development of these children. A better understanding of extra-temporal epilepsy is needed to help improving seizure free outcome in this large group of patients. doi:10.1016/j.clinph.2012.03.069
3. Dynamic effective connectivity of epileptic networks determined with high density EEG source analysis—G. Plomp d, R. Tyrand d, L. Astolfi b, B. He c, M. Seeck a, C.M. Michel d, S. Vulliemoz a (a Neurology – HUG, Geneva, Switzerland, b Sapienza University, Roma, Italy, c University of Minnesota, Minneapolis, Switzerland, d Faculty of Medicine, Geneva, Switzerland) Introduction: Analyzing the dynamic behaviour of epileptic networks could help to better understand the way pathologic neural activity propagates, and leads to spikes, seizures, and their electroclinical and cognitive manifestations, with implications for epilepsy surgery candidates. Methods: In 6 patients with temporal lobe epilepsy we studied effective connectivity of large-scale cortical networks at high temporal resolution around interictal spikes, recorded with high density (256 channels) EEG. The cortical electric source activity was obtained for 90 cortical regions of interest (ROI) using a distributed inverse solution. Multivariate, time-varying (millisecond resolution), and frequency-resolved (1–50 Hz) Granger causality analysis (Partial Directed Coherence) was applied to the source signal for all ROIs. In all patients subsequent intracranial recording or surgical resection was used for validation. Results: Information flow occurred predominantly in the theta and beta bands. The key driving structures where located in the anterior and medial temporal regions, with peak information transfer before the spike maximum. We found fast-varying connectivity patterns between the antero-medial and lateral temporal lobe and basal frontal lobe, but also transient transfer towards the contralateral temporal lobe. In two patients with a multifocal irritative zone, we found evidence of connectivity from the main anterior temporal driver towards the secondary spike focus remote from the epileptogenic zone. Conclusion: EEG-based time-varying effective connectivity of epileptic spikes provides a clear characterization of the epileptic networks that is concordant with invasive electro-clinical findings. This could have major clinical implications for tailoring resective, disconnective, and functional surgery. doi:10.1016/j.clinph.2012.03.067
4. Cerebral embolism in endarterectomy versus stenting for symptomatic carotid artery stenosis: The significance of plaque morphology on duplex ultrasound—A.B. Burow, P.L. Lyrer, M.A. Amort, P.J.N. Nederkoorn, M.M.B. Brown, R.S. Sztajzel, S.E. Engelter, L.H.B. Bonati (Queen Square National Hospital, London, United Kingdom, Academic Medical Center, Amsterdam, The Netherlands) Background: Carotid stenting (CAS) and carotid endarterectomy (CEA) may be complicated by cerebral embolism which often remains clinically silent. Unstable carotid plaques might increase the risk for peri-procedural embolism. We studied whether quantitative assessment of carotid plaque echogenity on ultrasound predicts the risk of cerebral ischaemia during CAS or CEA. Methods: In 50 consecutive patients with symptomatic carotid stenosis randomised to CAS (n = 26) or CEA (n = 24) in the International Carotid Stenting Study, semi-automated grey scale measurement of baseline carotid ultrasound images was performed. Greyscale median, percentage of plaque area <20th percentile of greyscale values, and an echographic risk index based on degree of stenosis and plaque area below the 20th percentile of grey-scale values were determined, both for the entire plaque and plaque surface. Brain MRI including diffusion-weighted imaging (DWI) was per-
e109
formed within 7 days before and 3 days after treatment as part of the ICSS–MRI substudy. The primary outcome on MRI was the presence of at least 1 new hyperintense DWI lesion after treatment. Results: In the CAS group, patients with new DWI lesions after treatment (n = 18) had significantly higher whole-plaque echographic risk indices at baseline (mean 0.1050) than patients without new lesions (n = 8; mean 0.0263; p = 0.012). GSM was 26.7 for patients with and 34.3 for patients without lesions (p = 0.163). Other measures of plaque echogenity did not differ significantly. In the CEA group, there were no significant differences in plaque echogenity measures between patients with (n = 2) and those without DWI lesions (n = 23). Conclusion: Our results show that among patients treated with CAS, the echographic risk index was higher in patients with new ischaemic brain lesions after treatment than in those without new lesions. Quantitative ultrasound plaque analysis may be helpful in estimating the risk of embolic complications in CAS. doi:10.1016/j.clinph.2012.03.068
5. Seizure control after epilepsy surgery: Experience in young children and adolescents—B. Jenny a, Y. El Hassani a, S. Momjian a, C. Pollo b, M. Seeck a, K. Schaller a (a Hôpitaux Universitaires de Genève (HUGs), Geneva, Switzerland, b Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland) Introduction: Surgery for pharmacoresistant epilepsy is well accepted as an efficient treatment for children suffering the debilitating consequences of repetitive seizures. The goal of this study was to analyse seizure control and complications after epilepsy surgery in our center. Methods: Data were retrospectively reviewed from 73 patients aged from 5 months to 16 years old who underwent epilepsy surgery at the Geneva University Hospital and Lausanne University Hospital between 1997 and 2011. Epilepsy surgery included temporal surgery (29 cases), extra-temporal surgery (32 cases) and hemispherotomies (12 cases). Three aged groups were identified: under 3 years old (18 cases), between 4 and 12 years old (35 cases) and between 13 and 17 years old (20 cases). Mean follow-up was 27.25 months (range 4–96 months). Results: The overall seizure-free rate at the time of follow up was 65.7% (48 out of 73 cases). Interestingly in children under 3 years old, the seizure free rate after surgery was 83.3% (15 out of 18 cases). Also, the seizure free outcome was significantly better for temporal epilepsy (79.3%) compared to extra-temporal epilepsy (56.2%) (p = 0.028, < 0.05). At least 50.6% of patients (37 out of 73 cases) had a reduction in their post-operative antiepileptic medication. Complications included five transient hemiparesis, two wound infections, one cerebral oedema after hemispherotomy, one extradural hematoma, one subdural hematoma after insertion of subdural grids and one intraventricular hematoma after hemispherotomy. Conclusions: These data highlight the good outcome and significant seizure free rate of epilepsy surgery at a very young age (children under 3 y/o). Efforts to promote epilepsy surgery in children are crucial since it significantly impacts on the cognitive development of these children. A better understanding of extra-temporal epilepsy is needed to help improving seizure free outcome in this large group of patients. doi:10.1016/j.clinph.2012.03.069