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Biomedical subjects

D Samson-Dollfus

Publications and source records attributed to D Samson-Dollfus.

At least 55 records · Page 3Linked to original sources
PubMed1983

[Spectral analysis of fast EEG rates in normal 6-to-16-year-old children].

Spectral analysis of EEGs from 208 school children aged from 6 to 16 shows two types of beta activity: anterior beta which is low in amplitude but increases in energy in response to eye opening and posterior beta which, like alpha, decreases in response to eye opening. After reviewing the role of the FFT in frequency analysis we conclude that anterior beta activity corresponds to the classic beta rhythm of visual analysis, while posterior beta activity probably represents harmonics of alpha or even theta activity. In any case, beta activity in the normal child is very low in amplitude and energy.

Adolescent↗
PubMed1983

[Electrophysiologic study of neonatal hypoglycemia prolonged by hyperinsulinism].

A case of neonatal hyperinsulinism with hypoglycemia is reported. The EEGs were abnormal because of a lack of sleep modulation. The CT scan showed pathological occipital hypodensities. The flashes VER were abnormal at 1, 2 and 6 months of age, chiefly on the right occipital lead and showing a possible lesion of the right retrochiasmatic pathways.

Brain↗
PubMed1983

Delta, theta, alpha and beta power spectrum of sleep electroencephalogram in infants aged two to eleven months.

Automatic sleep EEG analysis was performed on infants from 2 to 11 months of age. Partial power spectra of delta, theta, alpha, and beta 1 bands were studied as function of sleep stages, age, and time of the night. beta 1, alpha, and delta power spectra are significantly lower in paradoxical sleep (PS) than in quiet sleep (QS) whatever the age; but theta is lower in PS than in QS only after 5 months of age. delta, theta, and alpha power increase with age in QS. Only delta and theta are greater in the first half of the night than in the second half. beta 1 power does not differ significantly in stages 2 and 3 of QS, during the course of the night or as a function of age. Thus delta, theta, alpha may be the best spectral parameters for the maturation of quiet sleep EEGs during the first year of life.

Alpha Rhythm↗
PubMed1982

[Realization of a system which permits automatic analysis of sleep of infants (2-12 months)].

We have developed a system which permits automatic analysis of sleep of infants from 2 to 12 months of age. It is based on the calculation of a score on the basis of 6 parameters weighted according to their importance in determining the different phases of sleep. We use 3 EEG parameters derived from spectral analysis of the Cz-Oz derivation: total spectral energy (Hjorth activity), energy of the delta band, and energy of the beta band, and 3 polygraphic parameters: variability of muscle activity in each minute, variability of the respiratory frequency and presence or absence of rapid eye movements. The analysis provides a list of the sleep phases, minute by minute, and a traditional sleep diagram; we also calculate the successive appearances of the different sleep phases, in 10 min periods, and schematize these results in a diagram which shows the general trend of each sleep phase during the night. When compared with visual analysis, these results are satisfactory, since we observe on average 86.2% agreement in the differentiation of calm, paradoxical and transitional sleep, and 76.4% agreement in the differentiation of stages II, III and IV of calm sleep.

Electroencephalography↗
PubMed1982

[Several cases of EEG registration of epilepsy induced by television].

We present 6 cases of television epilepsy; there appear to be 2 distinct populations. The first group has seizures only when near the screen, is sensitive to the alternating appearance of odd and even lines and most often is not sensitive to photic stimulation at 50 Hz; the second group has seizures far from the screen and is sensitive to photic stimulation at 50 Hz. Therapeutic approaches are discussed for both groups.

Adolescent↗
PubMed1982

[Electroencephalographic surveillance during carotid endarterectomy].

Continuous EEG monitoring during 110 carotid endarterectomies showed transient or permanent abnormalities in 35 cases. In 13 cases, these abnormalities occurred during carotid clamping and led the surgeon to place a shunt in 8 cases. In 22 cases, electrical abnormalities of various types appeared outside the clamping period. Continuous EEG monitoring demonstrated that cerebral disturbances can occur at any time during the operative period. Thus, intra-operative EEG monitoring allows a better understanding of clinical signs which may be seen postoperatively.

Anesthesia, General↗
PubMed1981

[Visual evoked responses with flash pattern in normal subjects (author's transl)].

Visual evoked responses to flash pattern simulations have been observed in young healthy adults. Stimulations of whole visual fields (37 subjects) and half-fields (11 subjects) have been performed. These responses are reproductible from one subject to another and show very clear waves in the occipital and central regions. On central leads, whatever the stimulation (stimulation of total visual fields or half-fields), the responses are always the same: a negative peak at 70 msec. followed by a positive peak at 90 msec, then a negative peak at 116-120 msec. On occipital leads, stimulation of the whole visual field shows a diphasic response: a positive wave at 100 msec and a negative wave at 140-150 msec. However, half-field stimulation shows different responses on the ipsi- and contralateral hemispheres, with a disappearance of the positive 100 msec wave in the ipsilateral occipital region. Thus, flash pattern stimulations seem to be useful in clinical practice because they evoke different types of responses in occipital and central regions.

Adult↗
PubMed1981

[EEG analysis and prognosis in 125 cases of non-hyperpyretic seizures occurring in children under three (author's transl)].

Between 1955 and 1970 recordings were made from 125 children aged 1-36 months who had had a first epileptic seizure (non-hyperthermic). 100 of these children were followed up for from 5 to 20 years: 35 had had their first seizure before 1 year of age and 65 between the age of 1 and 3. Hypsarrythmia was more frequent under 1 year of age, whereas short diffuse spike and wave bursts were observed only after 1 year. However, localized spikes, asymmetrical or slow tracings as well as normal tracings were observed in both groups, without significant difference. A fatal outcome is more frequent when the first seizure took place before the age of 1 year. However, in our sample the intellectual development of the surviving children does not depend on the time of the first seizure. In any case the prognosis is unfavorable, since only 31 of the children followed up developed normally.

Age Factors↗
PubMed1980

[Aid to the diagnosis of epilepsy. Codification of EEG tracings for the characterization of detectable non-stationary phenomena].

The aim of automatic EEG analysis is to detect and class the significant events of the signal. For the detection phase an autoregressive model is developed giving rise to non-stationary points. The model used to analyse information in each event goes further than the problem of existence or non-existence. It is possible to understand qualitative aspects regarding the recognition of typical patterns of epilepsy such as 'spike and waves' providing a preliminary classification of the pattern. Such a classification based on sentence coding established from quantities provided from the model leads to a qualitative understanding of the phenomenon. The first results are presented.

Computers↗
PubMed1980

[Segmentation of an experimental signal from morphologic descriptors: application to the electroencephalogram].

Many signals can be defined as a background interrupted by events. Our studied signal, the electroencephalogram, belongs to a special field of experiments in which an expert interprets these events. To carry out automatically this interpretation we have to deal with different approaches, e.g. signal processing, pattern recognition and artificial intelligence. The aim is to research a special pattern with hierarchical cancelling of all the parts of the signal which cannot contain the pattern. To descriminate we have to define what we call a disparity and an analogy. We specify them in terms of morphological structures represented with syntactical rules. Here we present a method of segmentation based on local morphological differences which appear on the signal. We code these differences. The organisation of disparities allow us to separate the parts of the signal which cannot be considered as the background signal. Among these separated parts we research a special type of pattern. For this purpose we use syntactical rules that we built up on a learning set of pattern. These rules concern the elements of the code used for the disparities. We applied this study to electroencephalographic signals and to typical epileptic pattern as complex spikes and waves.

Computers↗
PubMed1980

[Application of correlation factors to the study of visual evoked potentials in multiple sclerosis (author's transl)].

A comparison is made between cerebral evoked potentials through the left and right eye by studying the correlation functions between the two visual responses obtained. Two values were retained: the correlation coefficient CO which shows the degree of similarity between the two curves, and the phase displacement D which indicates the duration for which a curve has to be shifted in relation to the other in order to resemble it as closely as possible. An original representation, in the form of a correlation/phase displacement diagram, is drawn for each subject, and enables easy separation of normal subjects from those with pathological conditions. This technique was applied to 20 normal subjects acting as controls and 40 patients with suspected or confirmed multiple sclerosis. In the latter group, anomalies were found in 67 p. cent whereas retrobulbar optic neuritis had been diagnosed in only 35 p. cent of cases. By reducing the sample to include only known or probable cases of MS, anomalies were found in 88 p. cent with retrobulbar optic neuritis known in only 51 p. cent. These results are comparable with those obtained by using previously described methods, but have the advantage of automatic readings which are completely objective.

Brain↗
PubMed1979

Electroencephalographic quantification by time domain analysis in normal 7--15-year-old children.

Automatic EEG analysis was performed on 239 apparently healthy school age children. The children were classed in 3 age groups: (1) average age of 7; (2) average age of 11; (3) average age of 15. A time analysis method, comparable to classical visual analysis, permitted quantification of the records. The mean amplitude, frequency and percentage time for alpha and theta rhythms were determined for each subject for fronto-central and centro-occipital derivations bilaterally. Records were performed during periods of rest with eyes open and eyes closed. During hyperventilation, records were taken with eyes closed. The normal ranges of parameters were determined by calculating their means and standard deviations, for each age group under each recording condition. Delta and beta rhythm values were not calculated, because of their rarity in this apparently normal sample. The precision obtained by automatic analysis could not have been obtained by means of classical visual analysis. The present findings suggest that the statistical analysis of well-defined groups of normal and pathological children could be of significant value.

Adolescent↗
PubMed1978

[EEG spectral analysis in normal children between the ages of 6 to 16. Choice and validation of the most significant parameters].

Numerous parameters have been proposed in order to describe the EEG power spectrum. Within the scope of an EEG study on the normal child between 6 and 16 years of age, the following problem had to be solved: given a group of 19 variables measured on 232 subjects in 5 situations, which of these variables best describe the population under examination. The algorithm proposed to answer this question is based on principal component analysis on the correlation matrix. Only 4 parameters are necessary to describe the EEG of a normal child of 6 to 16 years--these are Hjorth's parameters (activity, mobility and first order complexity) and alpha band power. They allow the observation of individual differences and the quantification for a given subject of the reaction to eyes opening, sensitivity to hyperventilation or even reactions that are difficult to perceive visually such as those resulting from doing arithmetic or vocabulary tests.

Adolescent↗
PubMed1978

[An automated study of EEG: a method of detection of non-stationary points].

The purpose of this paper is to present an automatic method of signal analysis. To help physicians in their diagnostics, this method is implemented on a minicomputer in order to detect non-stationary points in electroencephalograms. The signal is modelled with an autoregressive filter. The parameters of this filter are adapted at each step. Identification gives the best model in the sense of a cost function representing the mean square error of noise, which is estimated during the optimisation time-window. The cost function is expressed by a quadratic formula. This allows the use of a fast algorithm, the 'conjugate gradient method'. An original statistical test is developed to detect non-stationary points in the signal. The performance of this method is tested with artificial data to determine the sensitivity of method parameters. Detection using real data is presented.

Computers↗
PubMed1978

[Electroencephalographic approach to lateralization in children].

Electroencephalograms were recorded in 76 normal children between 10-12 years of age and several parameters were calculated from the results of spectral analysis. Sections of recordings which were free of artefacts, taken under different conditions (eyes open, eyes closed and during tests of mental arithmetic and vocabulary with the eyes closed were analysed. In these normal children, there was significant asymmetry of the alpha 1, beta 1, theta rhythms, and related parameters at rest, but the asymmetry was not necessarily found to correlate with the laterality of hand, eye, foot or all three. Vocabulary, and to a greater extent arithmetic significantly decreased alpha rhythms. Arithmetic affected both hemispheres equally but vocabulary depressed the alpha rhythms more obviously on the left.

Alpha Rhythm↗