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Quantitative EEG features predict outcome in postanoxic electrographic status epilepticus
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Abstracts / Clinical Neurophysiology 127 (2016) e18–e132
Quantitative EEG features predict outcome in postanoxic electrographic status epilepticus—B.J. Ruijter a, M.J.A.M. van Putten a,b, J. Hofmeijer a,c (a Clinical Neurophysiology, MIRA – Institute for Biomedical Technology and Technical Medicine, University of Twente, The Netherlands, b Departments of Neurology and Clinical Neurophysiology, Medisch Spectrum Twente, Enschede, The Netherlands, c Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands) Objective: To identify quantitative EEG features with prognostic significance in patients with postanoxic electrographic status epilepticus. Methods: From continuous EEG recordings of 46 subsequent patients with electrographic status epilepticus after cardiac arrest, five-minute epochs were automatically selected every hour. We assessed background continuity evolution from these epochs using a quantitative parameter. If epochs were visually classified as epileptiform, additional features were extracted, including relative discharge power, interdischarge suppression ratio, correlation between discharge waveforms, coherence, and Shannon entropy. Outcome at three months was categorized as good (Cerebral Performance Category 1–2) or poor (3–5). Results: Ten patients had a good outcome. All 27 patients with status epilepticus before reaching background continuity had a poor outcome. As compared with patients with good outcome, seizure patterns of patients with poor outcome showed higher relative discharge power (0.35 vs. 0.10, p < 0.001), higher interdischarge suppression ratio (0.32 vs. 0.07, p < 0.001), higher discharge waveform correlation (0.63 vs. 0.52, p < 0.001), higher coherence (0.32 vs. 0.20, p < 0.001), and lower entropy (5.4 vs. 5.9, p = 0.011). Conclusions: In patients with postanoxic electrographic status epilepticus, poor outcome can be predicted by quantitative analysis of seizure patterns and background continuity evolution. Key message: Quantitative EEG helps predicting outcome in postanoxic electrographic status epilepticus. doi:10.1016/j.clinph.2015.11.140
Parallel Session 26 New perspectives about the role of interictal epileptiform discharges in epilepsy
Why is understanding of mechanisms of interictal discharges important for clinical practice—M. de Curtis (Unit of Epilepsy and Clinical Neurophysiology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy) The relationship between interictal discharges and seizures in focal epilepsies is debated. Interictal spiking and other patterns either increase or decrease ahead of a focal seizure. It is likely that interictal events with different functional meaning with respect to seizure generation exist. The identification of the neurobiological mechanisms that control interictal patterns that exert either a precipitating or a protective action in focal ictogenesis may be relevant to develop new therapeutic strategies to anticipate or abort seizures. The differences between interictal and pre-ictal unit firing and population spike patterns will be reviewed in animal model of focal seizures and epilepsy and in recordings performed with intracranial electrodes in patients suffering from drug-resistant focal epilepsies, submitted to pre-surgical evaluation. doi:10.1016/j.clinph.2015.11.141
Interictal discharges and HFOs in intra-operative electrocorticography before and after resection—M. Zijlmans a,b (a Department of Neurology, University Medical Center Utrecht, Utrecht, The Netherlands, b SEIN – Stichting Epilepsie Instellingen Nederland, Heemstede, The Netherlands) Intra-operative electrocorticography is used to tailor the resection of the presumed epileptogenic cortex. Tailoring based on epileptiform discharges like spikes is under debate, while ictiform spike patterns are generally considered pathognomonic for epileptogenic tissue and will usually yield the removal of the underlying tissue. High frequency oscillations (HFOs; ripples: 80–250 Hz and fast ripples: 250–500 Hz) are new biomarkers of epileptogenic tissue which are considered to be specific for the epileptogenic zone. We studied the effect of resection on the electrocorticography recordings and the predictive value of pre-resection and post-resection events. We found no HFOs in the resection border, unlike spikes, which can arise due to the resection. We found, however, an increase in ripples in functionally eloquent areas, and presumed these were physiological ripples. We found that residual post-resection fast ripples were the only predictor for post-surgical seizures. Postresection fast ripples are especially predictive of postsurgical outcome if the pre-resection electrocorticogram showed fast ripples. This suggests that fast ripples in the electrocorticogram could be useful for tailoring epilepsy surgery. People need to consider the effects of propofol and be able to recognize perisurgical artefacts and signal analysis could assist the clinical use of HFOs in electrocorticography. doi:10.1016/j.clinph.2015.11.142
Detection of epileptic activity in absence of EEG interictal epileptic discharges—F. Pittau a, M. Genetti b, G. Birot b, M. Tomescu b, S. Baldini b, S. Vulliémoz a, C. Michel b, M. Seeck a (a EEG and Epilepsy Unit, Neurology Department, University Hospitals and Faculty of Medicine of Geneva, Geneva, Switzerland, b Functional Brain Mapping Laboratory, Department of Fundamental Neurosciences, University of Geneva, Geneva, Switzerland) Aim: To assess if the EEGs of epileptic patients without any detectable spikes contain the voltage specific epileptic map. Methods: Fifteen patients with pharmaco-resistant focal epilepsy were included. Six minutes of resting state EEG with and without any detectable spikes were selected from long-term recording (31-channels, ref:FCz). Resting-state EEGs from 48 healthy control-subjects were also recorded. For each patient EEG, we calculated the averaged spike and its voltage map. We fitted the spike map on (i) EEG of patient with visible spikes (ii) EEG of the same patient without any visible spike and (iii) EEGs of the 48 controls. The presence of the voltage epileptic map was characterized by: mean-correlation and Global Explained Variance (GEV). For these criteria statistical differences between (1) controls and EEG with spikes, and (2) controls and EEG without spikes were evaluated. Results: The patient-specific epileptic voltage map was significantly more represented in the spike-free EEGs of patients than in EEGs of healthy controls (GEV p = 0.029; mean-correlation p = 0.032). This difference was more accentuated for patient-EEGs containing spikes (GEV p = 0.001, mean-correlation p < 0.001).
Abstracts / Clinical Neurophysiology 127 (2016) e18–e132
Quantitative EEG features predict outcome in postanoxic electrographic status epilepticus—B.J. Ruijter a, M.J.A.M. van Putten a,b, J. Hofmeijer a,c (a Clinical Neurophysiology, MIRA – Institute for Biomedical Technology and Technical Medicine, University of Twente, The Netherlands, b Departments of Neurology and Clinical Neurophysiology, Medisch Spectrum Twente, Enschede, The Netherlands, c Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands) Objective: To identify quantitative EEG features with prognostic significance in patients with postanoxic electrographic status epilepticus. Methods: From continuous EEG recordings of 46 subsequent patients with electrographic status epilepticus after cardiac arrest, five-minute epochs were automatically selected every hour. We assessed background continuity evolution from these epochs using a quantitative parameter. If epochs were visually classified as epileptiform, additional features were extracted, including relative discharge power, interdischarge suppression ratio, correlation between discharge waveforms, coherence, and Shannon entropy. Outcome at three months was categorized as good (Cerebral Performance Category 1–2) or poor (3–5). Results: Ten patients had a good outcome. All 27 patients with status epilepticus before reaching background continuity had a poor outcome. As compared with patients with good outcome, seizure patterns of patients with poor outcome showed higher relative discharge power (0.35 vs. 0.10, p < 0.001), higher interdischarge suppression ratio (0.32 vs. 0.07, p < 0.001), higher discharge waveform correlation (0.63 vs. 0.52, p < 0.001), higher coherence (0.32 vs. 0.20, p < 0.001), and lower entropy (5.4 vs. 5.9, p = 0.011). Conclusions: In patients with postanoxic electrographic status epilepticus, poor outcome can be predicted by quantitative analysis of seizure patterns and background continuity evolution. Key message: Quantitative EEG helps predicting outcome in postanoxic electrographic status epilepticus. doi:10.1016/j.clinph.2015.11.140
Parallel Session 26 New perspectives about the role of interictal epileptiform discharges in epilepsy
Why is understanding of mechanisms of interictal discharges important for clinical practice—M. de Curtis (Unit of Epilepsy and Clinical Neurophysiology, Fondazione Istituto Neurologico Carlo Besta, Milano, Italy) The relationship between interictal discharges and seizures in focal epilepsies is debated. Interictal spiking and other patterns either increase or decrease ahead of a focal seizure. It is likely that interictal events with different functional meaning with respect to seizure generation exist. The identification of the neurobiological mechanisms that control interictal patterns that exert either a precipitating or a protective action in focal ictogenesis may be relevant to develop new therapeutic strategies to anticipate or abort seizures. The differences between interictal and pre-ictal unit firing and population spike patterns will be reviewed in animal model of focal seizures and epilepsy and in recordings performed with intracranial electrodes in patients suffering from drug-resistant focal epilepsies, submitted to pre-surgical evaluation. doi:10.1016/j.clinph.2015.11.141
Interictal discharges and HFOs in intra-operative electrocorticography before and after resection—M. Zijlmans a,b (a Department of Neurology, University Medical Center Utrecht, Utrecht, The Netherlands, b SEIN – Stichting Epilepsie Instellingen Nederland, Heemstede, The Netherlands) Intra-operative electrocorticography is used to tailor the resection of the presumed epileptogenic cortex. Tailoring based on epileptiform discharges like spikes is under debate, while ictiform spike patterns are generally considered pathognomonic for epileptogenic tissue and will usually yield the removal of the underlying tissue. High frequency oscillations (HFOs; ripples: 80–250 Hz and fast ripples: 250–500 Hz) are new biomarkers of epileptogenic tissue which are considered to be specific for the epileptogenic zone. We studied the effect of resection on the electrocorticography recordings and the predictive value of pre-resection and post-resection events. We found no
Detection of epileptic activity in absence of EEG interictal epileptic discharges—F. Pittau a, M. Genetti b, G. Birot b, M. Tomescu b, S. Baldini b, S. Vulliémoz a, C. Michel b, M. Seeck a (a EEG and Epilepsy Unit, Neurology Department, University Hospitals and Faculty of Medicine of Geneva, Geneva, Switzerland, b Functional Brain Mapping Laboratory, Department of Fundamental Neurosciences, University of Geneva, Geneva, Switzerland) Aim: To assess if the EEGs of epileptic patients without any detectable spikes contain the voltage specific epileptic map. Methods: Fifteen patients with pharmaco-resistant focal epilepsy were included. Six minutes of resting state EEG with and without any detectable spikes were selected from long-term recording (31-channels, ref:FCz). Resting-state EEGs from 48 healthy control-subjects were also recorded. For each patient EEG, we calculated the averaged spike and its voltage map. We fitted the spike map on (i) EEG of patient with visible spikes (ii) EEG of the same patient without any visible spike and (iii) EEGs of the 48 controls. The presence of the voltage epileptic map was characterized by: mean-correlation and Global Explained Variance (GEV). For these criteria statistical differences between (1) controls and EEG with spikes, and (2) controls and EEG without spikes were evaluated. Results: The patient-specific epileptic voltage map was significantly more represented in the spike-free EEGs of patients than in EEGs of healthy controls (GEV p = 0.029; mean-correlation p = 0.032). This difference was more accentuated for patient-EEGs containing spikes (GEV p = 0.001, mean-correlation p < 0.001).