Masaki Iwasaki

Detection of epileptiform activity by human interpreters: blinded comparison between electroencephalography and magnetoencephalography.

Summary:u2002 Purpose: Objectively to evaluate whether independent spike detection by human interpreters is clinically valid in magnetoencephalography (MEG) and to characterize detection differences between MEG and scalp electroencephalography (EEG).

Effects of eyelid closure, blinks, and eye movements on the electroencephalogram

OBJECTIVEnTo characterize the effects of the eyeball and eyelid positions during eyeblinks on electroencephalographic (EEG) potentials.nnnMETHODSnMovements of the upper eyelids and eyes were measured in two healthy subjects using the magnetic search coil technique during horizontal and vertical eye rotations, eyeblinks, and lid closure. Corresponding signal changes were recorded simultaneously on the electroencephalogram (EEG).nnnRESULTSnSpontaneous blinks produced small eye movements directed down and inward, whereas slow or forced blinks were associated with delayed upward eye rotations (i.e. Bells phenomenon); both types of blinks caused positive EEG potentials with bifrontal distribution maximum at Fp1 and Fp2.nnnCONCLUSIONSnIn prior reports, these positive EEG artifacts have been attributed to upward eyeball rotation during blinks-Bells phenomenon. By contrast, our findings indicate that movements of the eyelid contribute to a greater extent to these EEG potentials than do upward eyeball rotations.nnnSIGNIFICANCEnCare is required in attributing EEG artifacts to movements of either eyeball or eyelid, since our findings suggest that they both contribute to these potentials.

Accentuated cortico-cortical evoked potentials in neocortical epilepsy in areas of ictal onset.

ObjectiveTo determine whether patients with neocortical epilepsy show evidence for increased excitability measured by cortico-cortical evoked potentials (CCEPs) in ictal-onset regions.MethodsIn patients undergoing intracranial recordings with subdural electrodes for epilepsy surgery, we measured amplitudes, latencies, and stimulus thresholds of CCEPs near ictal onset zones (iCCEPs), and compared with adjacent neocortex not associated with ictal EEG (nCCEP). CCEP amplitude and latency measurements were made with each stimulation site, using graded stimulation intensities.ResultsTen patients were included in this study. CCEPs were recorded in eight of 10 patients. The first negative (N1) iCCEP amplitude was higher than that of nCCEP in seven of the eight patients. In the group analysis, this difference was statistically significant. In three of these patients, the difference was individually significant. In one patient, the amplitude was higher in nCCEP than iCCEP and the area selected as nCCEP was within primary eloquent cortex. There was no significant difference seen in latency changes or stimulus threshold.ConclusionsAccentuated CCEP amplitudes near ictal onset zones could reflect an increased excitability of the cortex associated with the epileptogenic zone in some patients with neocortical epilepsy. The response of the neocortex to low-frequency stimulation may vary depending on the presence or absence of intrinsic epileptogenicity.

P118: Difference in sleep architecture between left and right temporal lobe epilepsy

s of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S79 women, aged 40–54; mean: 49 years), admitted to the Neurological Department after generalized seizures, and 28 healthy controls (21 men, 7 women, aged 30–45; mean 37.5 years). All the subjects underwent EEG with further spectral analysis including absolute power of the five frequency bands: delta, theta, alfa, beta1 and beta2. Results: The patients in comparisons with the controls were characterized by significantly higher power of all five analysed bands (P<0.0001) in the majority of channels, except for alfa band in parietal regions, beta2 band in the left temporal region and delta band in right temporal region. Conclusion: The increased absolute power within all analysed frequency bands in alcoholic patients with recent epileptic seizures may suggest the state of the general cortical hyperexcitability. The influence of chronic alcohol abuse and epileptic seizures upon bioelectrical activity of the brain requires further investigations. P118 Difference in sleep architecture between left and right temporal lobe epilepsy M. Nakamura1, K. Jin1, K. Kato1, H. Itabashi1, Y. Kakisaka1, M. Iwasaki2, N. Nakasato1 1Tohoku University Graduate School of Medicine, Epileptology, Sendai, Japan; 2Tohoku University Graduate School of Medicine, Neurosurgery, Sendai, Japan Question: Sleep disturbance is common in patients with epilepsy. The abnormal sleep architecture is characterized by frequent shifts in sleep stages with numerous awakenings and longer duration of light sleep following sleep onset, especially in patients with temporal lobe epilepsy (TLE). However, any relationship between seizure lateralization and sleep macrostructure in patients with any type of epilepsy remains unknown. The present study compared sleep architectures in patients with left and right TLE (LTLE and RTLE). Methods: This study included 17 patients with TLE (7 men and 10 women aged 17 to 50 years) who underwent simultaneous polysomnography and long-term video EEG monitoring. Ten and seven patients were diagnosed with LTLE and RTLE, respectively. Sleep stages were scored based on the American Academy of Sleep Medicine criteria. Total sleep time, sleep latency, REM latency, sleep efficiency, time and percentage of each sleep stage, and apnea-hypopnea index were compared between LTLE and RTLE. Results: Percentage REM stage was significantly (p=0.021) lower in patients with LTLE (10.1±5.9%) than in those with RTLE (16.3±2.9%). Other parameters showed no significant difference between the two groups. Conclusions: Epileptic dysfunction of the left temporal lobe was associated with reduction of REM sleep. The present result contradicts a previous report that left hemispheric cerebral infarction was associated with higher percentage REM stage. P119 Feature pre-processing for neonatal seizure detection G. Bogaarts, E. Gommer, V. van Kranen-Mastenbroek, D. Hilkman, J. Reulen AZM Maastricht, KNF, Maastricht, Netherlands On Neonatal Intensive Care Units (NICU) many vital parameters are recorded. Automatic Electroencephalography analysis could enhance the Abstract P119 – Figure 1 application of NICU brain monitoring. Recently, a new seizure detectionP119 – Figure 1 application of NICU brain monitoring. Recently, a new seizure detection method was introduced using Support Vector Machines (SVM). Objective: Aim of our project is to further optimize SVM classification accuracy. Methods: First, a Kalman filter (KF) was used to remove noise from both feature and classifier output time series in order to reduce short false detections. Second, EEG baseline feature correction (BC) was introduced to reduce inter patient variability in feature distributions. The performance of the detection methods is evaluated on 56 single channel routine EEG recordings from 39 both term and pre-term newborns. The area under the receiver operating characteristics curve (AUC) is used to evaluate the performance of the classification method. Results: SVM without any of the proposed pre-processing steps achieves an AUC of 0.759. The highest AUC of 0.877 is achieved on baseline corrected features with a Kalman smoother used for training data pre-processing and a fixed-lag KF used to filter the classifier output.

P459: Electro-clinical features of focal epilepsy patients with postictal generalized EEG suppression

s of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S171 variants on the EEG. Recently, some genes or genetic polymorphisms have been associated with brain development and eventually with epilepsies associated with structural brain lesions. Thus, it is plausible that some of these genes might also influence epileptogenicity in patients with epilepsy. Accordingly, genes coding Discoidin Domain Receptor Tyrosine Kinase 2 (DDR2), Tescalcin (TESC), and High Mobility Group A Protein (HMGA2) were associated with brain volume, and might influence epileptogenicity. Objective: Investigate the association between DDR2, TESC and HMGA2 genes and interictal spike activity in temporal lobe epilepsy (TLE). Methods: Case-control study of 76 patients with TLE exploring the influence of polymorphisms rs10494373 of DDR2, rs7294919 of TESC and rs10784502 of HGMA2 on the incidence, distribution and lateralization of interictal epileptiform EEG of these patients. All individuals had an awake and asleep standard EEG recordings, and tracings were analyzed by experienced and certified electroencephalographers. Results: No association between rs10494373 of DDR2, and rs7294919 of TESC polymorphisms with EEG spike rates was found in TLE, regarding the EEG variables studied. However, presence of C allele in homozygosis in rs10784502 variant of HGMA2 was associated with significant less interictal discharges (p=0.008), in other words, presence of T allele in this specific polymorphism was associated with a doubling of discharges per minute, when compared with C allele in homozygosis (OR: 2.15±2.99 × 1.01±0.65). Conclusion: Our data allow us to hypothesize that variability in the HMGA2 gene might influence EEG interictal epileptiform activity and epileptogenicity in patients with TLE. We believe that further studies will shed some light on molecular mechanisms involved in the generation of EEG epileptiform activity. P459 Electro-clinical features of focal epilepsy patients with postictal generalized EEG suppression K. Jin1, H. Itabashi1, K. Kato1, Y. Kakisaka1, M. Iwasaki2, N. Nakasato1 1Tohoku University Graduate School of Medicine, Epileptology, Sendai, Japan; 2Tohoku University Graduate School of Medicine, Neurosurgery, Sendai, Japan Question: Postictal generalized EEG suppression (PGES) may be associated with sudden unexpected death in patients with epilepsy. Generalized tonic-clonic seizure (GTCS) is one of the well-known risk factors for PGES. However, which types of epilepsy are associated with PGES remain unclear. The present study investigated the electro-clinical features of focal epilepsy patients who suffered secondary GTCSs (sGTCSs) with PGES. Methods: We retrospectively reviewed 32 consecutive patients (13 men) with focal epilepsy aged 13 to 47 years, who presented with sGTCSs during long-term video EEG monitoring. PGES was determined using the previously published criterion of generalized absence of EEG activity of amplitude >10 μV. Patients with at least one sGTCS showing PGES were classified into the PGES (+) group (n=18, 56%). Electro-clinical findings including localization of epileptic foci and lateralizing signs on semiology were compared between the PGES (+) and (−) groups. Results: Temporal lobe epilepsy (TLE) was significantly (p G missense mutation in SCN8A. Electroencephalography (EEG) showed slight low-voltage background activity and occasional interictal epileptiform discharges in bilateral temporal areas during the first months. Ictal EEG was characterized by bilateral centrotemporal theta rhythm. Burst-suppression-like pattern in sleep recording was noticed at 11 months of age. He died at the age of 1 year and 5 months due to progressive respiratory failure during respiratory illness. Conclusion: Mutations in SCN8A can lead to EIEE with a broad spectrum of EEG and clinical features. Detailed phenotypic descriptions are needed to avoid unnecessary investigations and optimize the therapy. P461 Vagus nerve stimulation is beneficial in a patient with postural orthostatic tachycardia syndrome: a case report A. Bujan Kovac1, S. Hajnsek1, Z. Petelin Gadze1, S. Nankovic1, G. Mrak2, V. Sulentic1, I. Kovacevic1, I. Adamec1, M. Habek1 1University Hospital Centre Zagreb, Dept. of Neurology, Zagreb, Croatia; 2University Hospital Centre Zagreb, Dept. of Neurosurgery, Zagreb, Croatia Question: Postural orthostatic tachycardia syndrome (POTS) is defined by a heart rate increment of 30 beats/min or more within 10 minutes of standing or head-up tilt (HUT) in the absence of orthostatic hypotension. Vagal nerve stimulation (VNS) is a safe and effective adjunctive treatment for drug-resistant epilepsy when surgery is inadvisable. Limited data suggest that long-term VNS therapy might affect cardiac autonomic function. However, there are no data of the VNS utility in patients with POTS. Methods: A 29-year-old female patient was implanted with VNS due to pharmacoresistant epilepsy (elementary sensory-motor partial seizures of the left extremities and complex partial seizures of temporal origin with occasional secondary generalization. Couple of years she noticed palpitations and dizziness in standing upright that were relieved by sitting or lying flat. Brain MRI showed bilateral frontoparietal polymicrogyria and right subependimal nodular heterotopia. During the preoperative work-up autonomic nervous system testing revealed POTS that was refractory to life style modification measures. Results: One weak after implantation, VNS was initiated at 0.25 mA (duty cycle set to a 30-Hz signal frequency, a 500-ms pulse width, 30 sec of on-time, and 3 min of off-time). HUT done at one month and three months after implantation was normal. VNS was gradually increased to 1 mA which led to significant reduction in seizure rate and disappearance of orthostatic intolerance symptoms. Conclusion: To our knowledge, this is the first reported case of the positive VNS effect in patient with POTS. Further studies with a larger number of patients are needed. P462 Diffuse brain dysfunction in benign adult familial myoclonus epilepsy (BAFME) T. Hitomi1, K. Kobayashi2, T. Kondo2, R. Matsumoto3, K. Terada4, M. Kanda5, R. Takahashi2, A. Ikeda3 1Kyoto University Graduate School of Medicine, Clinical Laboratory Medicine, Kyoto, Japan; 2Kyoto University Graduate School of medicine, Neurology, Kyoto, Japan; 3Kyoto University Graduate School of Medicine, Epilepsy, Movement Disorders and Physiology, Kyoto, Japan; 4National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders, Epilepsy, Shizouka, Japan; 5Takeda General Hospital, Neurology, Kyotio, Japan Objectives: To clarify the clinical implication of posterior dominant rhythm

Cortical somatosensory evoked potential mapping

Publisher Summary Somatosensory evoked potentials (SSEPs) are electrical potentials generated in various parts of the somatosensory pathway in response to the stimulation given to a peripheral nerve. The initial cortically generated potential appears in the primary somatosensory area contralateral to the stimulated side. The distribution of the cortical responses is closely related to the functional sensorimotor representation of the stimulated body part from the patient. SSEPs provide important clues regarding the localization of the central sulcus as well as the somatotopic organization of the sensorimotor cortex. Precise definition of the somatosensory cortex is especially important in the surgical planning of patients with presumed overlapping of the sensorimotor strip and the epileptogenic zone. The standard technology for scalp-recorded SSEP has been described in detail. Scalp recorded SSEPs have significant limitations in terms of the localization of the somatosensory cortex. Multichannel recordings and the use of computerized source modeling may enable better localization than standard scalp recordings. Cortical SSEPs can be recorded through electrodes placed directly on the brain. The placement of a subdural array over the lateral or medial aspect of the frontoparietal cortex is usually done to localize the ictal-onset zone and for functional mapping purposes.