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Biomedical subjects

B Gueguen

Publications and source records attributed to B Gueguen.

At least 19 recordsLinked to original sources
PubMed1991

[Quantified EEG in the diagnosis of Alzheimer's type dementia].

79 subjects (mean age 70.2 ans, 31 males, 48 females) selected as probable dementia of the Alzheimer type, at the early stage of the disease and 17 normal aged people (mean age: 72.2, 5 males, 12 females) were recorded with a 16 channel computerized-EEG (C-EEG) with topographical analysis of the observed changes and with classical visual analysis of the EEG. Quite simple C-EEG parameters as mean dominant frequency (MF) and alpha to theta ratio are able to discriminate patients from normal with a greater accuracy than visual analysis. The values of 8.6 for the MF and 1.3 for the alpha/theta ratio are proposed as cut off values between normal and DAT patients. The topographical analysis appear to be of no additional usefulness in the discrimination of the two groups.

Aged↗
PubMed1991

[Comparison of SPECT and quantified EEG features in Alzheimer's type dementia].

Forty-one patients with probable dementia of the Alzheimer type (DAT) have been studied by computerized EEg (C-EEG) and single photon emission tomography (SPECT) using 123-IMP. Four groups have been distinguished according to SPECT hypoperfusion topography: frontal, temporo-parietal, fronto-parietal and fronto-temporo-parietal. C-EEG parameters were much more disturbed in the 2 latter than in the 2 former groups. Thus a normal C-EEG could indicate a dominant frontal or temporo-parietal form of DAT. Therefore some bias due to duration or rate of disease progression cannot be excluded. So far the important finding is that EEG changes are diffuse and do not reflect the topography of SPECT hypoperfusion questioning the value of EEG topographical analysis in DTA.

Aged↗
PubMed1991

[EEG value for the prediction of the evolution of Alzheimer's type dementia].

Twenty patients selected as probable dementia of the Alzheimer type (DAT) have been examined two times during a mean follow-up period of 14.5 months. Two groups have been distinguished at the end of this period: a cognitively impaired one and a stable one. EEG features at T1, at T2 or the difference T1-T2 does not allow an accurate and predictive discrimination between the two groups. But we cannot conclude that EEG is useless for prediction of the rate of progression of the disease in DAT because most of the cognitively stable patients are also stable for mean frequency. So mean frequency could be an interesting marker of evolutivity but this to be tested with more patients including more subjects reaching the severe stage of dementia.

Aged↗
PubMed1991

[Topographical analysis of endogenous evoked potentials in depressed old people and in patients with Alzheimer's type dementia].

Latencies, amplitudes and localization of the maximum of the peaks of late onset evoked responses have been studied in 3 groups of elderly people: normal, depressed and demented (probable dementia of Alzheimer type DAT) at the early stage of the disease. Evoked responses with an auditory oddball paradigm have been recorded with 16 electrodes in 2 situations: counting the target sounds, and motor response with measurement of the reaction time. No difference in amplitude was observed between the 3 groups. Only a significant difference for P3 latency was observed between the DAT and the depressed groups and only in the counting situation. The maximum P3 response was most often found on the anterior areas in the DAT group and in the posterior areas in the normal and depressed groups. The topographic localization of the P3 peak could therefore be of some help in the characterize of subjects with probable DAT at the early stage of the disease.

Aged↗
PubMed1988

[Caffeine and EEG mapping: effects of visuo-spatial task in healthy volunteers].

A group of 10 subjects, normal volunteers (6 men, 4 women), mean age 27.2 years, right-handers, has been selected for a double-blind study of caffeine effects (400 mg per os) versus placebo. One week delay separated the two EEG sessions quantified by spectral analysis. During each session (16 EEG channels, common reference), each subject was recorded four times: 2.5 min, in eyes-closed condition, under diffuse attention, followed by 2.5 min, during a visuo-spatial task ("eyes open" condition: presentation of a picture). These two EEG recordings were obtained before the oral administration and repeated 1 hr after the administration of caffeine or placebo. Individual and group results presented globally: 1) an increase in mean frequencies of alpha activity in "eyes closed" condition, and of delta activity in "eyes open" condition; 2) a decrease of alpha activity amplitudes (both RMS and % values) in both conditions; 3) a decrease of total RMS amplitudes in "eyes closed" condition; 4) an increase of relative % amplitudes for beta 2% fast activity in the "eyes open condition". These results characterize the psycho-stimulant effects of caffeine, especially over the left temporal area which was confirming an initial statistical hypothesis of specific cerebral local activation. The non-parametric permutation tests of Fisher, were not always reaching statistical significance for the same EEG channel quantified by one of the 17 analyzed spectral parameters, except on the left temporal area. During the visuo-spatial task, the decrease in alpha amplitudes (RMS and %) was also statistically significant, but over larger areas: over left and right temporal, central and parietal regions. In both conditions, eyes closed and eyes open, the alpha RMS amplitude was also decreased over the right anterior frontal area.

Administration, Oral↗
PubMed1988

[Clinical, electrophysiologic and endocrine effects of the perfusion of high doses of TRH in amyotrophic lateral sclerosis].

Eight patients with amyotrophic lateral sclerosis received 500 mg TRH by IV infusion, at a progressive rate during 3 hours. Only 3 patients noted subjective improvement of strength. Clinical muscular testing and H response study failed to show any change. Moreover modifications of the prolactin, growth hormone, TSH and T3 serum levels raise a question concerning the tolerance with long term utilization of TRH.

Acetylcholinesterase↗
PubMed1987

Vascular malformations of the spinal cord: intrathecal perimedullary arteriovenous fistulas fed by medullary arteries.

We studied eleven patients with intrathecal extramedullary arteriovenous fistulas identified by selective angiography and myelography. The fistulas were located on the surface of the cord, fed by medullary arteries. Angiography distinguished three separate types that gave identical clinical disorders. Therapeutic results of surgery and embolization allowed specific indications to be defined for treatment of each type of fistula.

Adolescent↗
PubMed1987

[Value of quantitative EEG and EEG mapping in medicine].

Quantitative EEG consists in digitising the EEG from one or several leads and then mathematically processing the signal usually by Fourier spectral analysis. A reduction of the digital information gives characteristic parameters (frequency, amplitude or power, asymmetry, etc.), which can themselves be averaged and submitted to different statistical analysis. Quantitative EEG is particularly suitable for clinical electropharmacology for the assessment of the profiles of psychotropic drugs, for pharmacokinetic correlations of dose-effect relationships and studies of drug bioavailability. The signals obtained from schizophrenic and depressed patients have well defined quantitative EEG characteristics: dissymmetry of the amplitude and hypovariability of the EEG signals. EEg mapping is performed by computer processing of 16 simultaneous EEG lead recordings. This new form of medical imaging is fast, relatively economical and non-invasive, and it is used in psychophysiology to study cognitive tasks and the states of vigilance and sleep. It is also used to study the EEG topography of cerebrovascular accidents, brain tumours, cranial trauma, cerebral degeneration and dementia, and the EEGs of psychiatric patients on psychotropic drugs. EEG mapping represents not only a static and statistical approach by drawing the averaged maps of groups of patients but also a dynamic approach by the recording of sequential individual maps presented as an animated film. The results of this method can be correlated with other medical imaging techniques used to investigate the central nervous system.

Brain Diseases↗
PubMed1986

[EEG mapping in partial epilepsy].

Even if mathematic treatment of EEG signals by Fast Fourier Transformation (FFT) in cases of transient epileptic discharges is still controversial, this method has been applied to 21 cases of epileptic partial seizures. Examples are shown, and compared to CT-Scan data. In 17 cases, EEG mapping identified alterations of basic activities upon a definite area. In addition, a focal peak of maximal alterations displacing itself into the limits of the whole epileptogenic area is demonstrated; it is furthermore suggested that the power spectrum keeps, especially during seizures, a peculiar ("combing") morphology, possibly specific of epileptic diseases.

Adolescent↗
PubMed1986

Severe chorea after acute carbon monoxide poisoning.

Ten days after an acute exposure to carbon monoxide, a 33-year-old woman exhibited severe chorea. CT scan revealed bilateral lucencies of the pallidum and anterior arm of the internal capsule. Chorea was successfully treated by chlorpromazine and did not relapse after treatment withdrawal. The mechanism of chorea in acute carbon monoxide poisoning is discussed.

Adult↗
PubMed1985

Chorea and polycythaemia.

Two patients with chorea and polycythaemia vera are described. The literature on this rare association is reviewed and its pathophysiology discussed.

Aged↗
PubMed1985

Neuronal responses in subfornical organ and other regions to angiotensin II applied by various routes.

Effects of Angiotensin II (AII) and of signals of hydromineral deficiencies on neuronal firing in the subfornical organ (SFO) and the surrounding regions of the rat were examined. AII was applied in three ways: electrophoresis, intracarotid injection, or intracerebroventricular injection. Seventeen SFO neurons (52%) were facilitated by electrophoretic AII and one (3%) was inhibited (AII-responding neurons). Neurons in other regions (cerebral cortex, nucleus triangularis septi, hippocampus, nucleus periventricularis) were also facilitated (23%) or inhibited (14%). Prostaglandin (PG)F2, a universal vasoconstrictor, produced an effect similar to that by AII on neuronal activity of the SFO and surrounding regions, and this effect was antagonized by (NO2-), a vasoplegic agent. Intracarotid injection of AII caused biphasic facilitation of SFO activity. The second increase correlates with changes in blood pressure. Intraventricular injection of AII caused drastic and long lasting excitation of SFO activity. Simultaneous intraventricular application of NO2- blocked the AII effect on SFO neurons but not on blood pressure. Hypovolemia or cerebrospinal fluid withdrawal that might cause mechanical stimulation of circumventricular organs increased SFO neuronal activity. These results are compatible with the vasoconstriction hypothesis of an indirect effect of AII through change in diameter of the vasa that surround neurons.

Action Potentials↗
PubMed1985

Electroencephalographic Cartography. I. By means of mini- or microcomputers. Reliability and interest of this electrical non-invasive brain imagery.

We have recorded control subjects, neurological and psychiatric patients (n = 217 sequences recorded over both hemispheres). Minicomputers (HP Fourier analyzer, HP 1000) for spectral analysis provided 10 spectral parameters over 5 spectral frequency bands (delta, theta, alpha, beta 1, beta 2, raw EEG). For each recorded sequence, 90 EEG maps could be computed over both hemispheres. Topo-EEGs were stored in an EEG image data bank. An EEG mapping microcomputer system linked with a digital polygraph (Alvar Electronic, REEGA 2000) has been used simultaneously. White noises have been fed into both computers for testing spatial resolution. Ten topo-EEGs have been recorded in control subjects and patients. The microcomputer system has provided very reliable topographical results when compared to similar maps generated by the minicomputer. A common average reference has been used. First clinical applications have been studied (brain strokes, brain tumors). The method appears very reliable in comparison with CT scans.

Adult↗
PubMed1983

Iontophoretic investigation of identified SFO angiotensin responsive neurons firing in relation to blood pressure changes.

Activity of 29 histologically identified units in the SFO was recorded in parallel to blood pressure monitoring. The responsiveness of these units to angiotensin II (AII) applied either iontophoretically or via the carotid artery (IC) was investigated together with the capacity of the vasodilator substance NO2- to block the AII response. Fifty-five% of the SFO units responded to iontophoretic application of AII (vs. 27% in the surrounding areas). SFO units were also activated by blood pressure depressions, either as a mirror image (type B) or only restricted to the initial descendent phase of the hypotensive wave (type A). But 8 of the 29 units responded in a mixed A and B fashion, i.e., dramatic firing in the very beginning of the hypotension followed by a sustained moderate response until recovery. Hypertensive spontaneous fluctuations rarely and inconsistently elicited an inhibitory response. An unexpected phenomenon of a hypotensive response following IC injections of low doses of AII was observed and used in this investigation. These observations together with the finding that vasoplegics inhibited unit firing suggest that the SFO is equipped with units able to sense a reduction in local vessels' calibre and fire in relation to it. When activated chemically, electrically or mechanically these units may then trigger hypertensive, antidiuretic and drinking responses.

Angiotensin II↗
PubMedDate not supplied

[Role of electroencephalography in the diagnosis of acute cerebral diseases].

It appears from a study of 100 cases of acute cerebral disease that electroencephalography is valuable as part of the diagnosis strategy and not only to establish the correct final diagnosis. This examination therefore plays a non-negligible role in neurological practice. In a number of diseases it provides information that no other examination can provide, being a dynamic, functional method of brain tissue analysis.

Acute Disease↗