P809: Altered connectivity patterns during partial seizures with different types of impaired consciousness as ictal correlate

P809: Altered connectivity patterns during partial seizures with different types of impaired consciousness as ictal correlate

Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 and medial sources can be detectable in frontal lobe ep...

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Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339

and medial sources can be detectable in frontal lobe epilepsy. This is the first in vivo demonstration derived from simultaneous subdural and scalp EEG recordings of the complementary significance of extensive source activation and higher subdural spike-to-background amplitude ratio in the detection of cortical generators in frontal lobe epilepsy. Our findings contribute to the decoding of interrelations between cortical sources and their scalp EEG correlates and thus to the interpretation of scalp EEG in the presurgical evaluation of refractory frontal lobe epilepsy.

P809 Altered connectivity patterns during partial seizures with different types of impaired consciousness as ictal correlate M. Gerez, A. Tello, E. Arollo, L. Castanedo, E. Suarez, C. Serrano Hospital Español de Mexico, Neurophysiology, Mexico City, Mexico Question: Are the connectivity patterns altered differently in different types of ictal consciousness impairment? Background: Consciousness is a central concept in epilepsy: transient loss characterizes generalized seizures and different types of consciousness impairment may occur during partial ones. Jackson postulated a “consciousness dissociation” caused by electrical disturbances at higher levels in hierarchical neural networks. The EEG breakthrough generated evidence of ictal experiential phenomena in focal epilepsies, raising several physiopathogenic hypotheses. Yet, even with intracranial recordings and electrical stimulation studies, the mechanisms of impaired consciousness remain elusive. Experiential phenomena defy focal interpretations. Current models consider brain function as the result of multiple processes in hierarchical modular assemblies with dynamical non-linear interactions. Flexibility and complexity are no longer obstacles within this framework. Methods: LORETA current source density correlations (CSDC) were calculated (Pearson) among Regions Of Interest (ROI) during EEG documented seizures with psychic content in 10 psychiatric patients, no history of epileptic or neurological disease. The Ictal Consciousness Inventory was applied scoring level (ICI-L) and content (ICI-C) of consciousness, psychotic features were extracted from the Positive and Negative Symptom Scale (PANSS-P), analyzed with ANOVA. Findings: Seizures defined by EEG ictal activity were accompanied by psychic changes in all subjects, no motor component. Psychic changes and CSDC patterns differed among patients. Decreased CSDC among structures of the Default Mode Network (DMN) were related to decreased ICI-L. Different patterns of increased CSDC among limbic and midfrontal ROIs were related to ICI-C and PANSS-P scores. Conclusions: Our findings suggest that: 1) various types of consciousness impairment can be ictal correlates in partial seizures, 2) ICI-L, ICI-C y PANSS-P may vary independently, 3) variations correlate with different patterns of altered connectivity among ROIs, 3) DMN structures modulate ICI-L, 4) ICI-C and PANSS-P are independently related to altered CSDC within networks known to be related to monitoring and integrative processes.

P810 Stereo-electroencephalographic invasive exploration in epileptic children less than 5 years old can successfully lead the surgery M. Chipaux 1,2 , G. Dorfmuller 1,3 , S. Ferrand-Sorbets 1 , M. Fohlen 1 , C. Bulteau 1,3 , J. Ternier 1 , O. Delalande 1 , D. Taussig 1 1 Fondation A. de Rothschild, Pediatric Neurosurgery, Paris, France; 2 Centre de Recherche de l’Institut du Cerveau et de la Moelle épinière, UPMC/INSERM UMR-S 975; CNRS UMR 7225, Paris, France; 3 INSERM, U663, Paris, France We reported a paediatric series of invasive intracranial electroencephalographic (EEG) explorations with depth electrodes in patients of less than 5 years old (group 1, n=21) presenting refractory focal epilepsy. Children were explored with invasive EEG before surgery in the past 2 years in our institution. We compared their data to the one obtained with children more than 5 years old (group 2, n=44), explored during the same period of time. In group 1, the mean age was of 39 months (range 20 to 60 months), and included 5 children presenting infantile spasms. In 24% of the group 1, scalp electrodes recorded bilateral EEG foci, and in 38%, multifocal interictal foci. Seizure onset was unique in 76% of the group 1, and multifocal inside a unique region in 19%. Therefore, the invasive exploration was wider in the group 1, as electrodes were implanted in at least 3 lobes and up to 4/5 lobes (76%). Only 2 patients were turned down for surgery after EEG,

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despite the great number of the patients (28%) with multifocal seizures onset. Subclinical seizures were very frequent since they are recorded in 67% of the children. In addition, the ictal onset was more heterogeneous in group 1 than in adults and the classic low voltage fast rhythms discharge could be missing. We were able to evoke seizures by electrical stimulation in 33% of the group 1. Cortical motor mapping was performed even in children less than 5 years old and motor response was evoked in 100% of the cases. After surgery, the follow-up lasted 26 months on average. The outcome in group 1 was Engel 1 for 76% of the children, whereas only 59% of the group 2 were seizure free. In conclusion, children younger than 5 years old could be explored with intracranial EEG as well as could the oldest ones, even if electric and clinical correlations were more difficult regarding to the age. Group 1 outcome after epilepsy surgery seemed better than with group 2, even if they showed multifocal regional abnormalities, both on scalp and intracranial EEG. Apart for 2 patients, the others had no clearcut limits on the MRI and the EEG led to more wide tailored resection than a simple lesionectomy. Suitability of stereo-EEG and more frequent MRI abnormalities in youngest patients allowed a better guidance of the surgical process.

P811 Pre-ictal changes of HRV rhythms in children with temporal lobe epilepsy K. Schiecke 1 , D. Piper 2 , F. Benninger 3 , H. Witte 1 , M. Feucht 3 1 Jena University Hospital, Friedrich Schiller University Jena, Inst. of Medical Statistics, Computer Sciences and Documentation, Jena, Germany; 2 Politehnica Univ. of Bucharest, Dept. of Applied Electronics and Information Engineering, Bucharest, Romania; 3 University Hospital Vienna, Epilepsy Monitoring Unit, Dept. of Child and Adolescent Neuropsychiatry, Vienna, Austria Question: This study was undertaken to demonstrate that a combination of time-variant, frequency selective, linear and non-linear approaches can ameliorate the analysis of heart rate variability (HRV) in patients with epilepsy in order to reveal premonitory information regarding an imminent seizure and to provide more information concerning the mechanisms leading to changes of the autonomic nervous system. The combined approach should allow new insights into specific short-term patterns of HRV during pre-ictal, ictal, and post-ictal states. Methods: 10 min epochs (5 min before: pre-ictal state, 5 min after seizure onset: seizure and post-ictal state) of pediatric patients (≤18 years at age) with clinically ascertained temporal lobe epilepsy (TLE) due to mesial temporal sclerosis (MTS) – all of them at least 12 month seizure free after temporal lobe surgery – were investigated. EEG data were collected during presurgical video-EEG-monitoring. The continuous Morlet-wavelet transform was used to explore the time-frequency characteristics of the HRV using spectrogram, phase-locking, band-power and quadratic phase coupling analyses. These results are completed by time-variant characteristics derived from a signal-adaptive approach. Advanced empirical mode decomposition was utilized to separate out certain HRV components, in particular blood-pressure-related Mayer waves (≈0.1 Hz) and respiratory sinus arrhythmia (≈0.3 Hz). Their time-variant non-linear predictability was analyzed using local estimations of the largest Lyapunov exponent (point prediction error). Results: 18 children (median age 9 years 4 months; median seizure length 88 s) were included. Approximately 80–100 s before the seizure onset timing and coordination of both HRV components changed. A higher degree of synchronization was found and with it a higher predictability of the HRV. All investigated linear and non-linear analyses contributed specifically to these results. Conclusion: Changes of organization (grouping) and signal properties of Mayer waves during the pre-ictal period can be seen as premonitory information regarding an imminent seizure in children with mesial TLE. Our approach serves as a starting point for further studies including not only HRV but also other autonomic parameters.

P812 Usefulness of movement and heart rate as physiological signals to detect nocturnal epileptic seizures J. van Andel, F. Leijten, K. Roes, J. Arends University Medical Centre Utrecht, Utrecht, Netherlands Background: Many research groups focus on automatic seizure detec-