P790: Sustained photic driving after the cessation of the flashes in epilepsy

P790: Sustained photic driving after the cessation of the flashes in epilepsy

Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 of this study is to assess if the type of electrode has...

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

of this study is to assess if the type of electrode has any influence on motor amplitude (baseline to peak) and distal motor latency. Methodology: We investigated in 10 normal young subjects (Male and female, age range: 20-40), measuring four commonly used motor nerves (median-Abductor Pollicis Brevis, ulnar-Abductor Digiti Minimi, peronealExtensor Digitorum Brevis and tibial-Abductor Hallucis). Five different electrodes with varying characteristics such as usability (disposable/reusable), fixed and variable inter-electrode distance, different surface areas and structure were used. These were 1. Standard Ag/AgCl EEG electrodes, 2. Disposable surface electrode Kendall Tyco, 12 mm, circular 3. Ambu Neuroline disposable surface electrode 15mm × 20 mm rectangular rounded edge, 4. Surface stick-on, disposable ECG electrodes 22mm × 22 mm square and 5. Medelec bar electrodes with fixed inter-electrode distance of 20 mm. Nerve conduction studies were performed using Kimura’s standard belly tendon protocol. Results: We conclude that there is no significant difference when using electrodes of size/shape with varying inter-electrode distances, provided standard belly-tendon protocol is used. However, Compound Motor Action Potentials are significantly lower using Medelec bar electrodes with fixed inter-electrode distance and this difference was minimal with medianAPB motor study. Distal Motor Latency was not found to be significantly different depending on the type of electrodes used. Conclusion: The findings support the use of these commercially available surface electrodes with varying inter-electrode distances in routine nerve conduction studies. However, Medelec bar electrodes, with fixed interelectrode distance, were found to be inferior in the majority of motor studies. References: [1] Lemkes, H. H., van der Kamp-Huyts, A. J., & van Dijk, J. G. (1996). Large electrodes improve nerve conduction repeatability in controls as well as in patients with diabetic neuropathy. Muscle & nerve, 19(6), 689-695. [2] Jonas, D., Bischoff, C., & Conrad, B. (1999). Influence of different types of surface electrodes on amplitude, area and duration of the compound muscle action potential. Clinical neurophysiology, 110(12), 2171-2175. [3] Kimura, J. (2001). Electrodiagnosis in diseases of nerve and muscle: principles and practice. Oxford university press.

Poster session 46. Epilepsy 3 P787 Epileptic signatures in cerebello-thalamic activity of the Cacna1atottering mutant mouse O. Eelkman Rooda, L. Kros, C. de Zeeuw, F. Hoebeek Erasmus Medical Centre, Neuroscience, Rotterdam, Netherlands Question: Hyper-synchronized thalamocortical network activity underlies spike-wave discharges (SWDs) in electrocorticogram recordings (EEG) during epileptic absence seizures. Cerebral regions involved in this type of epilepsy have been explored (e.g., Paz JT, et al., 2007, Polack PO, et al., 2007), but still, little is known about a cerebellar role in absence seizures (cf. Kandel and Buzsáki, 1993). We examined if the monosynaptic connection allows the cerebellum to mediate thalamocortical oscillatory activity and thereby control absence seizures. Methods: We set up experiments in homozygous tottering (tg) mice; a validated mouse model for absence epilepsy (Noebels et al., 1979). Awake, head-restrained tg mutants frequently show spontaneously occurring SWDs in EEG recordings. Simultaneously, we extracellularly recorded single-unit activity of neurons in the cerebellar nuclei and the downstream thalamic nuclei. In addition, we recorded the effects of optogenetic control of cerebellar output by virally encoded channelrhodopsin-2 on the thalamic activity as well as on the cortical EEG. Results: During absence seizures, we found that in a subset of recordings the action potential firing pattern of neurons in both cerebellar nuclei and thalamic nuclei were significantly modulated at 6-9 Hz, i.e., the representative frequency for SWDs in tg mutants. In addition, we were able to modulate the occurrence of SWDs by optogenetic control of the cerebellar output. Conclusions: Together, our study provides new insights in how cerebellar output is implemented in thalamocortical network activity and underline

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that this subthalamic input is of general importance for absence seizure epilepsy.

P788 Electro-clinical characteristics of epileptic seizures in preterm infants S. Janáˇcková, J. Rennie, S. Mathieson, R. Pressler Great Ormond Street Hospital for Children NHS Foundation Trust, Neurophysiology, London, United Kingdom Question: Although neonatal seizures have been evaluated in more detail over the last decade, seizures in preterm babies are still poorly described. In clinical practice aEEG rather EEG is often used to make the diagnosis. The aim of this study was to assess electro-clinical characteristics of seizures in preterm babies occurring before a corrected gestational age of 40 weeks. Method: In this retrospective study we analysed electroencephalographically documented seizures in 19 infants born prematurely between 24 and 36 weeks of gestational age (median GA30 weeks, sex ratio 0.9). Results: Our results showed that seizures are diagnosed later in preterm infants born before 32 weeks gestational age than in preterm infants born after 32 weeks gestational age. Median duration of seizures was of 60 seconds, increasing with corrected age. Seizures are focal or multifocal and can involve any part of the cortex. In the very premature infants, they usually stay more localised and involve smaller regions of onset. With the increasing post-conceptional age spreading becomes more frequent and later on also more widespread, giving evidence of the progress of myelination. The electrographic pattern also evolved with age. The maximal frequency of oscillation within the seizure increased with the corrected age which reflects maturation of the ion channels and neuronal network. Only one of nineteen infants displayed electro-clinical seizures, thus neurophysiologic monitoring is essential for accurate diagnosis of seizures in preterm babies. Conclusion: Our data indicate that seizures in preterm babies are shorter, involved smaller regions of onset and stayed more localised the younger the preterm babies were making diagnosis with aEEG difficult.

P789 Interictal EEG activity is associated with mood disorders in temporal lobe epilepsy J.A. Bragatti, C. Torres, P. Cherubini, S. Segal, M. Bianchin Hospital de Clinicas de Porto Alegre, Neurology, Porto Alegre, RS, Brazil Objective: Psychiatric comorbidities are frequent in temporal lobe epilepsy (TLE), and symptoms of these comorbidities may be related with epilepsy activity. Here we evaluate interictal EEG activity in TLE patients with or without psychiatric comorbidities. Methods: Cohort study of 78 patients with TLE, evaluating wake/sleep interictal scalp EEG. All subjects were submitted to psychiatric structured interview (SCID) for the diagnosis of lifetime psychiatric comorbidities. Four major diagnostic categories were studied: mood disorders, anxiety disorders, psychosis, and alcohol abuse. We then evaluated differences among interictal EEG activity in patients with or without these psychiatric comorbidities. Results: Non-frequent EEG interictal spikes, defined as less than one event per minute, were significantly associated with mood disorders in TLE (OR=5.20; 95%CI =1.05 - 9.12; p=0.02). Conclusions: Mood disorders in patients with TLE might be associated with low interictal spike frequency on EEG. Low intensity of seizure disorder has been associated with a decrease in interictal EEG discharges, and with an increase in psychiatric symptoms in TLE, a phenomenon known as forced normalization. Here we observed a neurophysiological correlate in line with forced normalization. Significance: Low spike index in TLE might be a neurophysiological substrate for the complex relationship between epilepsy and depression, as expressed by the phenomena of forced normalization and bidirectionality between the two entities.

P790 Sustained photic driving after the cessation of the flashes in epilepsy Y. Demura, A. Matsumoto, M. Kinoshita Utano National Hospital, Kyoto, Japan Question: What factors can be associated with sustained photic driving,

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

defined as harmonic driving lasting after the cessation of the flash, in patients with epilepsy? Subjects: Three-hundred and seventy-one patients with epilepsy (194 males), age 37±15 years old (mean ± SD), who visited epilepsy clinic and were recorded electroencephalography (EEG) with photic stimulation, were included. Controls subjects were 6 males and 5 females, age 36±13 years old. Methods: EEG was recorded with scalp electrodes set in International 10-20 system. Photic stimulation was performed by placing the stroboscope in front of the subjects’ eyes which were closed. The frequencies of repetitive photic stimulations were 3, 6, 8, 10, 12, 14, 16, 18, and 20 Hz, each delivered for 10 sec with the pause of 10 sec. Results: Sustained photic driving was notices in 31% of patients with epilepsy and 91% of normal controls. Duration of sustained photic driving was significantly longer in patients with epilepsy (243±59 ms in patients, 161±35ms in controls, p<0.005). By epilepsy classification, the duration was significantly longer in partial epilepsies (frontal lobe epilepsy, temporal lobe epilepsy, and parietal lobe epilepsy) and idiopathic generalized epilepsy than in normal controls (p<0.005). Conclusions: Sustained photic driving is a physiological phenomenon seen in normal subjects. Rarer occurrence or longer duration in patients with epilepsy may associate with their abnormality in synchronization or desynchronization.

P791 A case of temporal lobe epilepsy with sudden diarrhea T. Murai 1 , T. Tohyama 2 , M. Kinoshita 3 1 Kyoto City Hospital, Neurology, Kyoto, Japan; 2 Kyoto Min-iren Chuo Hospital, Psychiatry, Kyoto, Japan; 3 Utano National Hospital, Neurology, Kyoto, Japan Question: Can temporal lobe epilepsy manifest with repeated episodes of sudden diarrhea and loss of consciousness? Methods: A 63-year-old right-handed female presented with chief complaints of sudden diarrhea and loss of consciousness for almost three decades. The first attack occurred in her 30s and similar attacks repeated several times in a year. Her attacks comprised of abrupt abdominal discomfort, diarrhea, sudden emergence of old memories that she had played with her brother in her childhood, and loss of consciousness during defecation. She had no convulsion or automatism and fully recovered in a few minutes. Every time she was transferred to emergency hospital by ambulance, she had examinations such as blood test, head computed tomography, electrocardiogram, abdominal ultrasound, and electroencephalography (EEG), but no specific diagnosis was made. She was admitted to our hospital for further evaluation of epilepsy. Results: Vital signs, neurological examination, and blood tests showed no abnormal finding. During long-term video-EEG monitoring for forty hours she had no habitual event. Interictal EEG showed intermittent irregular delta waves and sharp transients regional left anterio-midtemporal area. Sharp transients were not as outstanding from background activities as to be definite epileptiform discharges, but they were reproducible in morphology and distribution, and appeared not only in sleep but also in awake. Brain magnetic resonance imaging was unremarkable. Brain Single photon emission computed tomography showed decrease of blood flow in left frontal and temporal lobes. Wechsler Adult Intelligence Scale-III showed decline of verbal comprehension. We diagnosed that the patient was suffering from partial epilepsy originating from left temporal lobe. Carbamazepin markedly improved her attacks. Conclusions: Temporal lobe epilepsy can manifest with diverse autonomic symptoms and signs. Abdominal sensations often herald the onset of epileptic seizures. Among them is an uncommon syndrome called abdominal epilepsy, in which gastrointestinal complaints are the primary or the sole manifestation of epileptic seizures. In patients who complain with diarrhea and other autonomic symptoms otherwise unexplained, a possible diagnosis of epilepsy should be considered.

(DTI) and Diffusion Tensor Tractography (DTT) in identifying abnormalities in MRI negative patients with cryptogenic extramesiotemporal focal epilepsies. Methods: 14 patients with cryptogenic extramesiotemporal focal epilepsy were investigated. DTI data was acquired on a GE Signa HDx 3T Scanner, using an acquisition scheme with 64 diffusion weighted directions, a bvalue of 1000m/s2 , 2.4 mm slice thickness and 2 mm in-plane resolution. Fractional anisotropy (FA) maps were investigated for focal changes and asymmetries. Streamline DTT of the whole brain was used as an exploratory method in the absence of a structural lesion and the number of reconstructed streamlines in homologous anatomical areas of the left and right hemisphere were compared. Asymmetries of more than 10% for FA maps and more than 20% for the streamline count were rated as a significant finding. Results: Asymmetries in the number of reconstructed streamlines were found in nine of the 14 patients (64%). In eight of them, these changes were consistent with the clinically suspected seizure onset zone, based on video-EEG-monitoring and nuclear medicine data, however, in two patients DTT indicated more widespread, hemispheric changes, beyond the seizure onset zone. FA maps show asymmetries beyond 10% in only one patient. In two patients, the seizure onset zone was confirmed in the area of DTT abnormalities by intracranial electrodes, the other patients are still awaiting invasive evaluation, including the one with discrepant DTI findings. Conclusions: These preliminary data show the potential role of DTI and DTT as complementary lateralizing and localizing imaging modality in the presurgical evaluation of cryptogenic extramesiotemporal epilepsy patients. We hypothesize, the observed changes reflect migration disorders, where heterotopic neurons disrupt the microstructural order of white matter underlying the seizure onset zone. Follow ups with intracranial electrodes and correlation with histopathology are required for further interpretation of these findings. DTT appears to be more sensitive than FA maps, and this method may be less sensitive in patients with small circumscribed focal pathologies compared to patients with a more widespread pathology.

P793 Consistency over time of electroencephalographic connectivity measures in temporal lobe epilepsy Y. Höller 1,2 , K. Butz 1 , A. Thomschewski 1,2 , P. Hoeller 1,2 , E. Trinka 1,2 Paracelsus Medizinische Privatuniversitaet, Universitaetsklinik fuer Neurologie, Salzburg, Austria; 2 Paracelsus Medizinische Privatuniversitaet, Spinal Cord Injury and Tissue Regeneration Center, Salzburg, Austria

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Objective: Connectivity biomarkers of the EEG have been shown to reflect seizure propagation and to indicate the source of abnormal hyperconnectivity. Nevertheless, it is questionable if these patterns are stable over time

P792 Diffusion tensor imaging and tractography identify structural changes in cryptogenic focal epilepsy J. Goc, E. Hartl, C. Catarino, A.-M. Loesch, J. Remi, S. Noachtar, C. Vollmar University of Munich, Munich, Germany Question: Here we investigate the contribution of Diffusion Tensor Imaging

Figure 1. GGC consistency for patients with right-lateralized TLE. x-axis: 2-40Hz; yaxis: correlations −1 to +1; green: not significant; red: significant correlations (FDRcorrected p<0.00004).