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Biomedical subjects

G Salamon

Publications and source records attributed to G Salamon.

At least 37 records · Page 2Linked to original sources
PubMed1993

A study of GABAergic system in Scrapie-infected hamsters after striatal microinoculation of the agent.

Experimental Scrapie in hamster is a simple, reproducible model of prion diseases that occur in humans and animals. Stereotaxic microinoculation (0.5 microliter) of the agent (263 K) into a specific cerebral structure (striatum) in hamster, previously developed in our group, gives the opportunity to further investigate the pathogenesis of these degenerative diseases and to more precisely define the brain areas and the groups of cells more vulnerable to the effects of the agent. In this model, early significant changes of glutamic acid decarboxylase (GAD) activity in striatum suggested a preferential alteration of the GABA system. The present study was focused on the effects of Scrapie agent directly injected into striatum on GABA neurons at the presynaptic level (GABA uptake) and at the postsynaptic level (GABAA receptors). The high-affinity [3H]GABA uptake is not changed in the Scrapie-injected striatum neither in the controlateral site and the kinetics (Km, Vmax) values are not statistically different for control and Scrapie-inoculated animals. The binding of [3H]GABA (Scatchard analysis) to cerebral membranes does not seem to be altered either at the local site of agent inoculation (striatum) neither at distance in the cerebellum: the affinity constant (Kd) to the ligand and the maximal number of receptor sites were of the same magnitude in control and Scrapie animals, but we do not have a statistical analysis. These effects are completely different of those of a neurotoxin. The present data suggest that the effects of prion agent may be very limited and very specific to some cellular mechanisms, without altering the whole cellular machinery, as recently shown in an in vitro model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Functional and magnetic resonance imaging correlates of callosal involvement in multiple sclerosis.

To investigate functional and anatomical features of callosal involvement in multiple sclerosis (MS), performances of 90 patients with definite MS and 25 matched normal control subjects were compared on three tasks exploring interhemispheric transfer of auditory, sensory, and motor information: a verbal dichotic listening task, a crossed tactile finger localization task, and an alternate finger tapping task. Each patient also underwent a magnetic resonance imaging (MRI) scan (1) to appreciate the extent of white-matter changes by a semiquantitative evaluation of hemispheric brain MRI hyperintensities and (2) to measure the degree of total and regional callosal atrophy using an automatized method of partition of the midsagittal callosal area. Interhemispheric transfer and/or integration was impaired in patients with MS for all modalities explored and proportional to both degree of callosal atrophy and diffusion of white-matter lesions. Moreover, in good agreement with data obtained from partial commissurotomy studies, performance on each functional task was predominantly associated with atrophy of one part of the callosum, namely left-ear dichotic suppression with the posterior callosal region, alternate finger tapping with the anterior region, and cross-localization with midanterior and posterior regions. Finally, a subgroup of patients without MRI white-matter hyperintensities also showed significant impairment of callosal function and relative atrophy of the callosum. These findings suggest the potential clinical value of callosal involvement in MS and the usefulness of MS as a model of interhemispheric disconnection.

Adolescent↗
PubMed1993

PET study of voluntary saccadic eye movements in humans: basal ganglia-thalamocortical system and cingulate cortex involvement.

1. The purpose of this work was to explore the cortical and subcortical mechanisms underlying the execution of voluntary saccadic eye movements in humans. 2. Normalized regional cerebral blood flow (NrCBF) was measured using positron emission tomography (PET) and H2(15O) bolus intravenous injections in four right-handed healthy volunteers at rest and while performing self-paced voluntary horizontal saccadic eye movements in total darkness. 3. Magnetic resonance imaging of each subject's brain was matched to PET images, allowing the detection of activation in individually defined anatomic regions of interest. Cortical regions were drawn according to gyri limits; subcortical structures were also defined. 4. Self-paced saccadic eye movements elicited bilateral NrCBF increases in the lenticular nuclei, including putamen and globus pallidus, and in the thalamus. At the cortical level, we found bilateral NrCBF increases in the precentral gyrus, the superior part of the median frontal gyrus that corresponds to the supplementary motor area. There was also a significant NrCBF increase in the cerebellar vermis. 5. Right fusiform and lingual gyri, right insula, and left cingulate gyrus were also activated during the execution of saccades. 6. These results indicate that the classical basal ganglia-thalamocortical motor loop previously described for skeletal movements may also be involved in simple saccadic eye movements in humans.

Adult↗
PubMed1992

Cortical region of interest definition on SPECT brain images using X-ray CT registration.

We present a method for brain single photon emission computed tomography (SPECT) analysis based on individual registration of anatomical (CT) and functional (133Xe regional cerebral blood flow) images and on the definition of three-dimensional functional regions of interest. Registration of CT and SPECT is performed through adjustment of CT-defined cortex limits to the SPECT image. Regions are defined by sectioning a cortical ribbon on the CT images, copied over the SPECT images and pooled through slices to give 3D cortical regions of interest. The proposed method shows good intra- and interobserver reproducibility (regional intraclass correlation coefficient approximately 0.98), and good accuracy in terms of repositioning (approximately 3.5 mm) as compared to the SPECT image resolution (14 mm). The method should be particularly useful for analysing SPECT studies when variations in brain anatomy (normal or abnormal) must be accounted for.

Blood Flow Velocity↗
PubMed1992

[Interhemispheric transfer in multiple sclerosis. Morphofunctional correlations].

Signs of cerebral disconnection, especially left ear suppression to dichotically presented verbal stimuli, have been reported in multiple sclerosis patients and found to be correlated to morphological atrophy of the corpus callosum on magnetic resonance imaging. To reinvestigate this issue, 26 patients satisfying criteria for definite multiple sclerosis were proposed 3 tasks aimed at evaluating interhemispheric function: a dichotic listening task, a motor finger-tapping task and a sensory transfer task. Performance at these tasks suggested impaired callosal function in MS patients, compared to normal controls. Callosal morphology was assessed on midsagittal MRI sections using a digitalised method of partition of the callosal area into 6 subregions and automatized surface measurements. Results of correlations between task performance and callosal areas showed a significant correlation between total callosal atrophy and severity of interhemispheric impairment on each functional task. Moreover, impaired motor transfer was specifically related to atrophy of the anterior callosal regions. These results suggest that MS patients may constitute a suitable population to studying interhemispheric transfer of information through the callosal commissure and that this approach may be useful in the clinical management of MS patients.

Adolescent↗
PubMed1992

Value of MRI in the morphological evaluation of tumors of the third ventricle.

The detection or suspicion of a tumoral expansive process in the third ventricule is usually performed by MRI. The contribution of MRI to the diagnosis is unquestionable in view of its accuracy in the topographical characterization of these lesions and in the detection of small formations. The great histological variety of tumours in that region may result in different treatments which can be associated. MRI, therefore, plays an important role in pretherapeutic morphological evaluation. Fifteen patients with tumour of the third ventricle were examined by MRI before treatment. The results of these examinations were compared with the pathological data and the therapeutic procedures: ventricular shunting, stereotactic needle biopsy, radio- or chemotherapy and surgery. MRI cannot provide a formal histological characterization, but it can individualise some categories of tumours, give details on the walls of the third ventricle (notably in the case of bifocal pineal and suprassellar lesions), visualize the paths of CSF flow and predict the need for cisternoventriculostomy, and detect venous structures in the vicinity of the great cerebral vein which might result in post-biopsy and post-surgery complications.

Adolescent↗
PubMed1991

Effects of handedness and sex on the morphology of the corpus callosum: a study with brain magnetic resonance imaging.

In view of conflicting data in the existing literature, we examined 53 normal subjects using a handedness questionnaire and callosal area measurements obtained from midsagittal MRI images. The callosum was found to be significantly larger in nonconsistent right-handers (NCRH), especially in its anterior half and especially for males. A significant hand x sex interaction, favoring consistent right-handed (CRH) females, was also found for the posterior midbody, a region known to house interhemispheric fibers connecting the right and left posterior association cortices. These results (1) confirm Witelson's (1985) first findings on postmortem specimens; (2) validate a dichotomy between CRH and NCRH rather than simply considering the writing hand, as was the case in most other similar studies; and (3) suggest that at least two different sex-related--probably hormonal--factors may be acting during the callosal development, one explaining the larger anterior half in NCRH males and the other the larger posterior midbody in CRH females.

Adolescent↗
PubMed1991

Topographical study of supratentorial brain tumors.

The topographic analysis of supratentorial brain tumors must answer the following questions: location of the tumor, its extension, its being infiltrative or well localized and especially the relationships with the main functional areas such as the speech areas, the sensori-motor area, and the visuel areas. Also the topographic analysis may help to approach the diagnosis of nature. The neuroradiological procedures include the CT, the angiography and especially the MRI in sagittal and coronal sections, with gadolinium enhancement. The anatomical accuracy is obtained using the bicommissural plane and superimposition techniques according to the Talairach's Atlas and anatomical sections and MRI superimposition with angiography. 3D volumic reconstruction is of considerable contribution for the topographic analysis of a cerebral tumor.

Angiography↗
PubMed1991

Astrocytic tumours.

Astrocytic tumours are frequent, accounting for nearly 50% of all brain tumours. They are divided into three groups: benign astrocytomas, anaplastic astrocytomas and malignant glioblastomas. The usual clinical manifestations of benign astrocytic tumours are epileptic seizures, whereas those of glioblastomas are rapidly progressing neurological deficits. These lesions show fairly characteristic neuroradiological features which have been largely studied. Injections of iodine-based or paramagnetic contrast media are important since they help in tumour grading: low-grade tumours are not enhanced, while glioblastomas are almost invariably enhanced. MRI seems to be indispensable for the study of astrocytic tumours: it provides an excellent anatomical analysis of the lesion during preoperative or pretherapeutic evaluation, and it is the only available method to confirm low-grade lesions that have passed unnoticed or have merely been suspected at CT. To avoid missing these tumours, every adult presenting with recent onset epileptic seizures should be explored by MRI using T2-weighted spin-echo sequences.

Adult↗
PubMed1991

Oligodendrogliomas.

Oligodendrogliomas are tumours developed from oligodendrocytes. They may be pure or associated with astrocyte proliferation. They are usually benign, but their malignancy grade is varied. These tumours affect middle-aged adults and are characterized by their slow growth and their fairly suggestive neuroradiological features which are those of a large, calcified, poorly enhanced, peripheral frontal lesion. Computerized tomography and magnetic resonance imaging are suitable complementary methods to characterize the tumour and evaluate its extension.

Adult↗
PubMed1991

Magnetic resonance imaging in gangliogliomas and gangliocytomas of the nervous system.

Gangliogliomas and gangliocytomas are rare and benign neuronal tumors which affect young subjects. This study concerns 3 cases of ganglioglioma and 3 cases of gangliocytoma explored by CT and MRI and confirmed by pathological examination. The most typical CT image was that of an often calcified contrast-enhanced cystic tumor. At MRI, each tumor emitted a low-intensity signal on T1-weighted sequences and a high-intensity signal on T2-weighted sequences. Contrast enhancement after gadolinium injection was frequent. Neuroradiology is not specific, and these tumors are usually diagnosed at pathology. However, the diagnosis may be considered in young patients with a history of old, drug-resistant partial epilepsy and having a contrast-enhanced, calcified cystic lesion in the temporal lobe or the cerebellum.

Adolescent↗
PubMed1990

[Gadolinium-DTPA in the study of intracranial tumors in the adult].

Thirty intracranial tumours were explored by MRI, using T1- and T2-weighted sequences, before and after intravenous injection of Gd-DTPA. Two-thirds of the intra-axial tumours were accurately detected on one section plane by MRI without Gd-DTPA, but in one quarter of the cases Gd-DTPA only delineated precisely the tumour. On the other hand, Gd-DTPA failed to detect certain tumours (benign gliomas) or showed only a small part of them (mixed grade gliomas), while they were detected by MRI without contrast injection. However, in such cases Gd-DTPA was useful for the stereotaxic biopsy of the tumour. Gd-DTPA appears of lesser interest in extra-axial tumours. Gd-DTPA is thus valuable for the neuroradiological diagnosis of brain tumours, particularly to evaluate the grade of gliomas and to confirm the diagnosis of recurrent growths.

Adult↗
PubMed1990

[Standardization of the anatomic study of the brain stem in x-ray computed tomography and magnetic resonance imaging].

The presence of flexures between the mesencephalon, pons and medulla oblongata implies the definition of specific orientations of axial sections for each level of the brain stem. These axial sections have to be perpendicular to the axis of the corresponding segment. For the mesencephalon, we have defined an axis corresponding to a straight line of best fit to the mesencephalic anatomical axis; the whole of the rhombencephalon has been referred to an axis taken through the pons and the intracranial medulla that is tangential to the floor of the IV ventricle. Identical reference planes can be obtained in CT by programming, on the scout view of the skull, perpendicular sections of the clivus that allow the study of the axial aspect of the mesencephalon, with sections at - 7 degrees through Chamberlain's line for visualization of the same aspect of the rhombencephalon. We have thus defined the referential planes to analyse every level of the brain stem using reproducible axial sections, able to be applied to different patients as well as to different examining techniques (TDM, MRI).

Adult↗
PubMed1989

Spontaneous dissection of both extracranial internal carotid arteries.

Neurological examination and Doppler sonography of a 50-year-old patient were suggestive of a spontaneous dissection of the left internal carotid artery (left-sided headaches, amaurosis fugax, Horner's syndrome and hemispheric stroke). Four-vessel angiogram performed several days after the onset of the symptoms showed dissection of both extracranial carotid arteries, more pronounced on right side where the dissection was clinically asymptomatic. Angiogram follow-up demonstrated a recanalization of both carotid arteries. A review of 15 other documented reports indicates that bilateral internal carotid dissection is usually associated with fibromuscular dysplasia. A large majority of cases does not clinically differ from unilateral carotid artery dissection.

Carotid Artery Diseases↗
PubMed1989

Magnetic resonance imaging of the brain stem. Anatomico-radiological correlations.

Magnetic resonance imaging of 30 normal volonteers' posterior fossae was performed on a CGR Magniscan machine with a magnetic field strength of 0.5 Tesla. We chose the inversion recovery signal with a Tr of 2,000 ms, a TE of 21 ms and an inverse time of 500 ms. This sequence gives a better definition of the grey matter, the white matter and the CSF. To study the brain stem we suggest 8 horizontal and 3 sagittal sections.

Brain Stem↗
PubMed1989

[Digital arteriography using an intra-arterial route in vertebrobasilar insufficiency. Comparison of iopromide 300 and ioxaglate 320 mgI/ml].

During intra-arterial digital subtraction angiography of the vertebral and basilar arteries, 24 patients were included in a prospective double-blind randomized trial comparing a new non-ionic contrast medium, iopromide 300 and an ionic low osmolar medium, ioxaglate 320 mgI/ml. There was a statistically significant reduction in the number of adverse effects observed with Iopromide 300, particularly in terms of unwanted movements, source of image quality degradation.

Angiography, Digital Subtraction↗