Clinical EEG (electroencephalography)最新文献

The intravenous olfaction test with thiamin propyl disulfide (TPD) is a simple procedure widely used in Japan. An olfactory stimulus is provided by intravenous injection of TPD (2 ml) over the course of 20 sec. The subject smells n-propyl mercaptan (a decomposition product of TPD discharged from the blood into alveoli) in expired air after treatment. In this preliminary study we recorded electroencephalograms (EEGs) in normal subjects during three stages: 1) eyes-closed rest (prestimulus), 2) olfactory sensation after TPD injection, and 3) disappearance of sensation. In each of these stages, we calculated and compared EEG powers according to the band components of each electrode position. This study was designed a) to evaluate by frequency analysis EEG changes during olfactory sensation after TPD injection, and b) to identify the most significant changes in EEG power according to frequency band and electrode location. During the intravenous olfactory stimulation, alpha 2 and beta 2 waves were activated over the frontal and temporal regions. After disappearance of olfactory sensation, these waves decreased in the same regions. EEG powers returned to prestimulus levels.

Most previous studies of the neurophysiological effects of caffeine have focused on the effects of caffeine ingestion, and few studies have examined the effects of caffeine withdrawal. This open study evaluated the quantitative EEG (QEEG) changes occurring during a 4-day period of abstinence in subjects who habitually consume 300 mg or more of caffeine daily. Thirteen subjects underwent QEEG studies during their usual caffeine consumption (baseline) and on days 1, 2, and 4 of a 4-day period of caffeine abstinence. Ten of the subjects underwent a second QEEG on day 4 that consisted of a period of recording after reinstitution of caffeine. A comprehensive analysis of multiple quantitative variables was performed for each study during the abstinence period and compared to the variables obtained at baseline for each subject. Changes occurring during caffeine abstinence included: 1) increases in theta absolute power over all cortical areas, 2) increases in delta absolute power over the frontal cortex, 3) decreases in the mean frequency of both the alpha and beta rhythm, 4) increase in theta relative power and decrease in beta relative power, and 5) significant changes in interhemispheric coherence. Most of these changes tended to return to pre-abstinence baseline levels rapidly after resumption of caffeine consumption. The caffeine withdrawal state affects a number of neurophysiological variables. Further investigation of the neurophysiological aspects of caffeine withdrawal using placebo controlled double blind assessment methods is warranted.

The sources of different EEG frequencies were studied in 25 normal children and 46 learning disabled (not otherwise specified) children between 7 and 11 years old. The EEG sources were computed using Frequency-domain Variable Resolution Electromagnetic Tomography which produces a three dimensional picture of the currents at each EEG frequency. Significant differences between groups were observed. LD children showed more theta activity (3.5 to 7.02 Hz) in the frontal lobes and control children more alpha (9.75 to 12.87 Hz) in occipital areas. These results may support the maturational lag hypothesis, as the neurobiological cause of learning deficiencies not otherwise specified.

EEGs from 16 patients with stroke in three different stages of evolution were recorded. EEG sources were calculated every 0.39 Hz by frequency domain VARETA. The main source was within the delta band in 2 out of 4 chronic patients, and in 67% of the patients in the acute or subacute stages when edema (cytotoxic or vasogenic) was present. Moreover, all patients showed abnormal activity in the theta band. Sources of abnormal activity in cortical or corticosubcortical infarcts were located in the cortex, surrounding the lesion. At the site of the infarct, a decrease of EEG power was observed. Sources of abnormal theta power coincided with edema and/or ischemic penumbra.

In this retrospective study 67 patients with SSPE seen between the years 1980 and 1998 were reviewed. Using the criteria of SSPE diagnosis (clinical signs, characteristic EEG patterns, high titres of measles antibodies in the serum and CSF), the patients were divided into two groups. Group A fulfilled all criteria, however, due to the inability of measuring measles antibody before 1987, it was not possible to observe the third criterion in Group B. Among 67 patients, groups A and B consisted of 51 boys and 16 girls ranging in age between 1 to 23 years, mean age 13.1. The male/female ratio was 3.1. The periodic EEG complexes (PCs) were usually bilateral, synchronous and symmetrical. PC amplitude asymmetry was seen in 12 patients and 2 patients had no PC synchronization between the hemispheres. Six patients had more than one form of PC. Delta activity in anterior hemispheres after PC was seen in 40 patients, mostly in stage 2A. Thirty-two patients had focal epileptiform abnormalities in multiple locations at every stage but most frequently in frontal, central and temporal regions. One patient had PC over both hemispheres and periodic lateralized epileptiform discharges (PLEDs) over the right hemisphere. The EEG findings described and observed in our study do not seem to be specific to SSPE but these findings were not atypical or unusual.

The present study was conducted to examine and compare interhemispheric EEG coherence at rest and during photic stimulation (PS; 5, 10 and 15 Hz) in 30 younger subjects aged 22.1 +/- 2.2 (mean +/- S.D.) and 25 elderly subjects aged 56.8 +/- 4.9. The elderly subjects had significantly lower coherence in the resting EEG for the delta, theta, alpha-3, beta-1 and beta-2 frequency bands. In contrast, EEG analysis during PS showed that elderly subjects had significantly higher coherence in the frequency corresponding to PS at 15 Hz. In addition, when we examined the changes in coherence from the resting state to the stimulus condition (i.e., coherence reactivity), elderly subjects had significantly higher coherence reactivity to PS at 15 Hz. These findings suggest a low interhemispheric functional connectivity in elderly subjects under non stimulus conditions and a high connectivity during photic stimulus.

EEGs and behavioral responses were studied in two sex matched groups of 58 epileptic and 20 healthy children between 8 and 12 years of age, during the execution of a go-no go CPT (X; A-X) task to determine transitory cognitive impairment (TCI) incidence. Paroxysmal discharges were found on 87.9% and 5% of the EEGs in the epileptic and control groups respectively, with no differences related to sex. The predominant EEG findings with respect to paroxysmal discharges were the association of two or more types of paroxysms with frequency higher than 5/minute, an average duration less than 0.5 second and topographical distribution over temporal-parietal-occipital areas without significant interhemispheric differences. TCI was detected in 36.2% of epileptic children. The epileptic group showed significantly higher numbers of behavioral errors and longer reaction times (RTs) in relation to the control group. Analyzing RTs on the two blocks of the task, linear discriminant analysis showed an acceptable classification of TCI incidence between groups.

Wavelet based signal analysis provides a powerful new means for the analysis of nonstationary signals such as the human EEG. The properties of the discrete wavelet transform are reviewed in illustrated application examples. The continuous wavelet transform is shown to provide better detection and representation of isolated transients. An approach to extract features of edges and transients from the continuous wavelet transform is outlined. Matching pursuit is presented as a more general transform method that covers both transients and oscillation spindles. A statistical model for the continuous wavelet transform of background EEG is found. A spike detection system based on this background model is presented. The performance of this detection system has been assessed in a preliminary clinical study of 11 EEG recordings containing epileptiform activity and shown to have a sensitivity of 84% and a selectivity of 12%. The spatial context of epileptiform activity will be incorporated to improve system performance.

EEGs were recorded on 21 konzo subjects (median age 17 years) and 13 of their close healthy relatives (median age 41 years). Konzo subjects were clinically selected and classified according to the WHO criteria. Standard waking EEG recordings were performed according to the International 10-20 System. Slowing of the background activity with theta activity was the most common abnormality (57%). The more clinically severely affected the konzo subject, the more often generalized EEG abnormalities were seen. None of these abnormalities were considered specific for konzo nor related to the duration of the disorder; however, the findings indicate involvement of the cerebral cortex.

Multifocal independent spike syndrome (MISS) is an identifiable electroclinical syndrome, which combines intractable motor seizures, mental retardation and multifocal independent spike discharges. Similarities to the Lennox Gastaut syndrome cause frequent misdiagnosis; however, MISS is a distinct electroclinical syndrome in children with a better prognosis and a different EEG pattern. We report an 8-year-old boy with MISS, whose intractable seizures were completely controlled for the first time with tiagabine as add-on therapy. Tiagabine should be studied further in the treatment of intractable multiple seizures of childhood.