Basic elelctrophysiology of the electroencephalography

Although neuroimaging techniques and other diagnostic procedures has been developed, electroencephalography (EEG) is still very important for the evaluation of various brain diseases and functional studies of human brain. EEG is formed mainly by spatial and temporal summations of postsynaptic potentials generated from a large population of pyramidal cells that can be considered as a collection of oscillating dipoles. EEG shows continuous rhythmic oscillation depending on sleep-waking state. Alpha rhythms are generated in cortical areas acting as epicenters with local spread, although the precise cellular mechanism is still unknown. Its been known that neurons in the nucleus reticular thalami are the pacemakers of sleep spindle. Alterations in the circuit of the reticular nuclei-thalamocortical relay neuron-cortical neuron are responsible for generalized spike and wave complexes. At the intracellular level, large paroxysmal depolarizing shifts produce focal epileptic spikes. Slow waves of EEG appear to be related to thalamocortical and/or corticothalamic deafferentation. The interpretation of routine EEG requires a well training from a qualified EEG teacher and reading adequate amount of EEG under supervision. Frequent misinterpretations of routine EEG have been observed in both local clinics and general hospitals. The most common findings of normal routine EEG misinterpreted as abnormal are normal variants and artifacts of various sources. There are considerable variations of normal EEG rhythms and pseudoepileptiform discharges. Eyeball movements produce prominent or subtle EEG changes over the frontal regions that are sometimes hard to be differentiated from abnormal slow waves over that region. Systematic approach was described for a good interpretation of routine EEG.OAIID:oai:osos.snu.ac.kr:snu2003-01/102/2014017262/3SEQ:3PERF_CD:SNU2003-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM:

Cognitive Dysfunctions in Patients With Severe Obstructive Sleep Apnea Syndrome: Neuropsychological Test and Event-Related Potential Study

Background: Patients with obstructive sleep apnea syndrome (OSAS) show variety of dysfunctions in cognitions including general cognitive function, attention, and frontal lobe and executive function. However, there is no consensus on the main features of the cognitive dysfunction in OSAS patients. So we performed neuropsychological tests and event-related potential (ERP) studies in patients with severe OSAS to evaluate the cognitive dysfunctions and changes of auditory and visual P300. Methods: Twenty-eight men with severe OSAS (apnea hypopnea index (AHI)=63.1±}17.8/hr) and 16 age, sex, educationmatched normal controls (AHI=2.9±}1.8/hr) underwent neuropsychological tests and ERP studies. Results: Patients with severe OSAS showed deficits in corsi block forward and backward test during neuropsychological evaluation, and delayed latency and decreased amplitude of auditory P300. There were significant correlations between auditory P300 amplitudes and digit span forward or corsi block forward test scores, and between visual P300 amplitudes and digit symbol test scores. Conclusions: These findings suggest that severe OSAS patients may have deficits in attention and short-term memory, and abnormal auditory P300.OAIID:oai:osos.snu.ac.kr:snu2008-01/102/2014017262/5SEQ:5PERF_CD:SNU2008-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM:

Spatio-temporal distribution & propagation of temporal lobe seizures: application of nonlinear mutual cross prediction

Background : Nonlinear mutual cross prediction (MCP) characterizes ynamic interdependence among nonlinear systems. MCP also reveal relative strength of the coupling between systems, thus provides information about the direction of interdependence. The aim of this study is to apply MCP algorithm to multi-channel EEG and to characterize spatio-temporal pattern of seizure. M e t h o d s : We analyzed MCP of EEG of three medically intractable temporal lobe epilepsy patients, who underwent temporal lobectomy (left 2, right 1). Asymmetry of nonlinear cross predictability between channels was investigated. Five epochs of interictal EEG free from epileptiform discharge(s) and of ictal EEG were analyzed. R e s u l t s : In interictal period, both frontal and occipital region appeared a weak driving force while awake and this driving force was further weakened during sleep. Before the onset of the seizure (preictal phase), the intensity of driving system became slightly stronger around seizure foci in 3 out of 8 seizures while no significant change was seen on the naked eyes. However this change was dim and not continuous. At the onset of seizure (ictal phase), 5 out of 8 seizures showed strong driving force around seizure foci. Three seizures without significant change initially had strong driving force as synchronous seizure discharges became built-up and spreading to surrounding areas in the middle of seizure. All seizures showed ipsilateral frontotemporal strong driving force and centroparietal response system, which was typical spatio-temporal distribution of MCP. Conclusion : MCP analysis may be a useful method for detecting spatio-temporal distribution and propagation pattern in temporal lobe epilepsy.OAIID:oai:osos.snu.ac.kr:snu2002-01/102/2014017262/2SEQ:2PERF_CD:SNU2002-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM:

Ictal Hyperperfusion of Brain Structures Related to Ictal Dystonic Posturing in Temporal Lobe Seizures

Although dystonic posturing (DP) during temporal lobe seizures is known to be related to basal ganglia activation, the mechanism of the dystonic posturing has not been investigated in greater details . Methods: Thirty-two patients with mesial temporal lobe epilepsy (TLE) underwent ictal and interictal SPECTs. They were classified into two groups: 1) DP with ictal dystonia during ictal SPECT (N=15) and 2) Non-DP without dystonia (N=17). Ictal-interictal SPECT subtraction was performed as follows: co-registration, intensity normalization, subtraction, thresholding and then an overlay to SPGR MRI. The presence and intensity of ictal hyperperfusion were determined in frontal lobe, basal ganglia, temporal lobe and insular cortex. Results: The incidences of ictal hyperperfusion in DP vs. Non-DP were caudate nucleus [80.0%(12/15 patients) vs. 0% (0/17), p=0.001], putamen [93.3% (14/15) vs. 48.2% (8/17), p=0.005], globus pallidus [53.3% (8/15) vs. 23.5% (4/17), p=0.082], thalamus [80.0% (12/15) vs. 41.2% (7/17), p=0.026], insular cortex [46.7% (7/15) vs.23.5% (4/17), p=0.051], orbitofrontal [46.7% (6/15) vs. 35.3% (7/17), p=0.053], medial frontal [6.7% (1/15) vs. 18.7% (2/17), p=0.621], dorsolateral frontal [13.3% (2/15) vs. 18.7%(2/17), p=0.737] in the hemisphere of epileptic side. In patients who showed ictal hyperperfusion in striatum and thalamus, the average intensity of hyperperfusion in DP vs. Non-DP was caudate nucleus 1.67 vs. 0.0, putamen 2.20 vs. 1.05, globus pallidus 1.2 vs. 0.65, thalamus 2.00 vs. 0.88 in the epileptic hemisphere. Conclusions: Caudate nucleus as well as putamen appeared to be important for producing ictal dystonia during TLE seizures. The greater intensity of ictal hyperperfusion in putamen, caudate nucleus and thalamus seems to be related to ictal dystonia.OAIID:oai:osos.snu.ac.kr:snu2003-01/102/2014017262/5SEQ:5PERF_CD:SNU2003-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM:

Cortical Representation to Odorant Stimulation: Statistical Non-parametric Mapping of Low Resolution Electromagnetic Tomography (LORETA)

Background: Although olfactory stimulation has been known to produce effects on human mood and cognition, the specific EEG patterns of activity was reported diversely. The purpose of this study was to investigate EEG changes by odorant using low resolution electromagnetic tomography (LORETA) in young healthy subjects. Methods: The EEG's of nineteen (10 males, 9 females) non-smoking right-handed college students were recorded after odorant stimulation. A nineteen-channel EEG was recorded referenced to linked ears before and during olfactory stimulation. Olfactory stimulation was presented with lavender essential oil by blotter method. The LORETA power was computed from ten 2-s epochs, separately for the different EEG frequencies. The power values were logarithmically transformed and paired sample t-tests were done for each voxel and frequency band (1.5-30 Hz). Statistical results were displayed 3-dimensionally on the standard brain template. Results: All subjects experienced positive feelings (relaxed and pleasant) by olfactory stimulation with lavender oil (p<0.01). The LORETA power of theta and alpha band was increased in the dorsolateral and medial frontal areas, predominantly in the posterior cingulate gyri. The alpha LORETA power was also increased in bilateral orbitofrontal regions and the left perisylvian region including the insular cortex. Beta power was increased in the posterior cingulated gyri and mesial temporal region, predominantly on the left side. Conclusions: These results suggest that olfaction associated with emotional feeling might induce brain electrical power changes not only in the limbic system but also in the neocortex with lateralization to the dominant hemisphere.OAIID:oai:osos.snu.ac.kr:snu2004-01/102/2014017262/1SEQ:1PERF_CD:SNU2004-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM:

Memory Lateralizing Values of Different Stimulus Types in Wada Test

Background: We studied the accuracy, lateralization criteria of Wada test in patients with temporal lobe epilepsy(TLE). We also evaluated material specific memory and determined the stimulus which can classify best between right and left TLE among four different types of stimuli. Methods: We examined Wada memory performance in 33 patients(15 left, 18 right) with TLE who underwent surgery and who were good seizure outcome at least 1 year follow-up. Twelve stimuli consited of figures, written words, geometric designs and real objects were presented after Amytal injection. The recognition memory test was performed at 10 minutes after the injection and hemisphere memory performance of each stimulus and total stimuli were obtained by(number of stimuli recognized / number of stimuli presented x 100%). Classification rate, best stimulus for lateralization, and suitable lateralization criteria were determined by discriminant analysis and Chi-square test. Hemispheric memory difference of each stimulus was analyzed by paired-sample Student's t-test in left temporal lobectomy(LTL) and right temporal lobectomy(RTL) groups. Results: No significant difference was observed in pre-Wada memory score and in IQ between LTL and RTL group. The classification rate of Wada test in terms of lateralization by discriminant analysis was 81.82%. The accuracy was 75.8% at 10% and 15% lateralization criteria and was 63.6% and 45.5% at 20% and 25% lateralization criteria, respectively. Figure was the most useful among four types of stimuli to classify TLE. Analysis of hemispheric memory according to stimuli revealed that memory difference between hemisphere was significant only for figure in LTL group(p=0.027). In RTL group, all 4 stimulus types had significant hemispheric memory difference (figure, p=0.000; written word, p=0.000; geometric design, p=0.000; real object, p=0.000). Conclusions: Wada test is a reliable method for lateralizing seizure foci in TLE. To get optimal results, lateralization criteria should be determined by statistica Key Words: Wada test, lateralization, material specific memory, TLE which have an influence on lateralizing seizure foci.OAIID:oai:osos.snu.ac.kr:snu1998-01/102/2014017262/3SEQ:3PERF_CD:SNU1998-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM:

SIMPLE PARTIAL STATUS EPILEPTICUS LOCLIZED BY SPECT SUBTRACTION IN CHRONIC CEREBRAL PARAGONIMIASIS

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Electro-clinico-pathologic Relations of Epileptogenic Foci in Cavernous Angioma

Background and Purpose: Cavernous angiomas are frequently encountered in patients with intractable partial epilepsies. Cavernous angioma can make highly epileptogenic foci and dual pathology. Although it is generally thought that the epileptogenic activity originated in neuronal populations adjacent to the lesion, little is known as to the exact location of the epilepsies on electophysiologic, clinical and pathologic view. We investigated nine intractable epilepsy patients with cavernous angioma regarding relation of EEG, semiology and pathology to verify where are the epileptogenic foci in cavernous angioma. Methods: We included 9 intractable epilepsy patients with cavernous angioma who had been were undergone video-EEG monitoring. They were aged from 15 to 49 years(average:36.7+15.7)and had cavernous angioma in temporal, frontal lobe, or multiple areas(temporal:7, frontal:1, multiple:1 patients). Four patients had invasive EEG study including subdural and/or depth electrodes. Six patients had undergone epilepsy surgery. We analyzed seizure history, semiology of their seizures, interictal and ictal EEG. To know dual pathology, MRI including hippocampal volumetry, invasive EEG, and pathology were studied. Results: Four patients had multiple auras. Eight patients had complex partial seizures and one had right foot clonic seizure, which were related with the location of cavernous angioma. In scalp EEG, ictal recording showed definite EEG changes, but 3 patients had no definite EEG change in some seizures. In invasive EEG with subdural and/or depth electrodes , interictal spikes were more frequently detected than scalp EEG and ictal EEG revealed not only 3 different ictal onset zones in 3 patients but also EEG seizures without clinical events in 3 patients. Regarding dual pathology, mesial temporal involvement was detected in 2 patients in MRI. Among 6 surgery patients 4 patients including 3 patients with normal hippocampus in MRI had hippocampal or dentate gyral change in pathology. Among 4 patients with invasive ictal EEG, 3 patients including 1 patient with normal hippocampus in MRI and pathology had mesial temporal involvement in ictal onset zones. Conclusion: Cavernous angiomas can make multiple epileptogenic foci around themselves and often dual pathology of hippocampus, which can be easily detected by invasive ictal EEG but not by imaging and even by pathology. And the foci can have frequent EEG seizures, which do not make clinical events. Precise localization of epileptogenic foci in cavernous angioma were needed to have good medical and surgical treatments.OAIID:oai:osos.snu.ac.kr:snu1998-01/102/2014017262/1SEQ:1PERF_CD:SNU1998-01EVAL_ITEM_CD:102USER_ID:2014017262ADJUST_YN:NEMP_ID:A079623DEPT_CD:801CITE_RATE:0DEPT_NM:의학과SCOPUS_YN:NCONFIRM: