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Biomedical subjects

J F Le Bas

Publications and source records attributed to J F Le Bas.

At least 55 records · Page 3Linked to original sources
PubMed1996

Case report: pseudotumoral brain lesion as the presenting feature of sarcoidosis.

Sarcoidosis rarely presents as an intracranial mass lesion. We report the case of a patient presenting a disturbance of cognitive functions in whom CT and MRI demonstrated a large right fronto-temporal mass lesion with contrast enhancement and surrounding marked oedema, highly suggestive of a brain tumour. The diagnosis of neurosarcoidosis was made after stereotactic biopsy of the lesion.

Biopsy↗
PubMed1996

[Relationship between anatomic lesions of the temporal lobe and temporal lobe epilepsy].

A structural lesion of the brain is a frequent finding in intractable partial epileptic patients. We analyse anatomo-electro-clinical characteristics of 58 patients in which MR showed a lesion inside the temporal lobe. They are 29 males and 29 females with a mean age at surgery of 23.5 +/- 10.7 years (2.6-45.9). The mean epilepsy duration is of 13.4 +/- 8 years (1.3-35.5), with a mean seizure frequency of 28.7 +/- 43.6 per month, with a great inter-individual variability (from 3 per month to 15 a day). The minimum follow-up is 3.5 years. A video-EEG monitoring was performed in 21 cases, while a stereo-EEG investigation was judged mandatory in 26. On the basis of anatomo-electro-clinical correlations and of the results of presurgical investigations, the epileptogenic area was proved to be temporal in 49 cases, temporal but controlateral to the lesion in 1, and at least bilobar in 8 patients.

Adolescent↗
PubMed1995

Effect of parkinsonian signs and symptoms of bilateral subthalamic nucleus stimulation.

In monkeys rendered parkinsonian, lesions and electrical stimulation of the subthalamic nucleus reduce all major motor disturbances. The effect of electrical stimulation of the subthalamic nucleus was assessed in three patients with disabling akinetic-rigid Parkinson's disease and severe motor fluctuations. Quadripolar electrodes connected to a pulse generator were implanted in the subthalamic nuclei on both sides. Patients were evaluated with the unified Parkinson's disease rating scale and timed motor tests. 3 months after surgery, activities of daily living scores had improved by 58-88% and motor scores by 42-84%. This improvement was maintained for up to 8 months in the first patient operated upon. One patient was confused for 2 weeks after surgery, and another developed neuropsychological impairment related to a thalamic infarction which improved over 3 months. In one patient, stimulation could induce ballism that was stopped by reduction of stimulation. This is the first demonstration in human beings of the part played by the subthalamic nuclei in the pathophysiology of Parkinson's disease.

Electric Stimulation Therapy↗
PubMed1995

1H MRS of human brain abscesses in vivo and in vitro.

Five patients, each with a brain abscess, were examined by means of 1H MR spectroscopic imaging in vivo. The aspirated pus was analyzed in vitro by means of 1D and 2D COSY 1H MRS. In addition to resonance lines from compounds (lactate, alanine and lipids) often found in the spectra from intracranial tumors, resonance lines were detected from a number of markers of infectious involvement (acetate, succinate, and various amino acids). These results suggest that 1H MRS in vivo might contribute in establishing noninvasively a differential diagnosis between brain abscess and tumor.

Acetates↗
PubMed1995

Original oblique sections of the retroperitoneum: radio-anatomic basis.

The authors present oblique sections of the retroperitoneum adapted to the morphology of each patient, which affects both the liver and the organisation of the retroperitoneum. This original method involve two incidences for studying the left and right retroperitoneum separately with vertical sectional planes. The authors postulate that the orientation of the retroperitoneal viscera depends on the degree of hepatic development, so these incidences are chosen with reference to axial sections of the portal bifurcation and the middle hepatic v.: the two vascular landmarks of the liver. Anatomic and radiologic studies confirm the reliability of these landmarks and their easy application in modern imaging. Such new data improve our understanding of the classical topographic anatomy of the retroperitoneum. These oblique sections promote the radiologic study of the portal and systemic vessels, renal pedicles, suprarenal glands and pancreas.

Hepatic Veins↗
PubMed1995

Intracranial gradient-echo and spin-echo functional MR angiography in humans.

PURPOSE: To investigate the predominance of venous signal intensity at 1.5-T gradient-echo (GRE) functional magnetic resonance (MR) imaging of motor activity and to demonstrate the contribution from task-induced changes in flow velocity to the functional MR imaging signal intensity. MATERIALS AND METHODS: Functional MR imaging of motor activity was performed in healthy volunteers. In a first examination, conventional two-dimensional GRE blood oxygenation level-dependent (BOLD) functional MR imaging techniques were used, and the image planes were carefully positioned with respect to the veins that responded to the motor task. In a second examination, two-dimensional spin-echo (SE) techniques were used, and the image planes were oriented axially and measured in a sequential multisection manner. The areas of hyperintensity on functional MR images were eventually processed by means of maximum intensity projection. RESULTS: Functional MR angiograms were obtained in both examinations. The possibility to generate SE functional MR angiograms demonstrates that venous inflow effects may contribute substantially to signal intensity in conventional two-dimensional GRE BOLD functional MR imaging of motor activity. CONCLUSION: Veins have a substantial role in BOLD functional MR imaging of motor activity.

Adult↗
PubMed1995

[MRI aspects of cerebellar hemangioblastomas. Apropos of 9 cases].

Nine patients with haemangioblastoma of the posterior cerebral fossa were explored by computerized tomography (CT), then by magnetic resonance imaging (MRI) with enhancement by gadolinium in 4 cases. Following a review of clinical and laboratory data, the radiological images are detailed and distributed into three forms: cystic with mural nodule, solid, and annular. The usefulness of the different imaging techniques is specified, and the stress it put on the need to look for multiple sites in the entire central nervous system.

Adult↗
PubMed1995

[A new X-ray source for medical imaging and radiotherapy research: synchrotron radiation].

Whether for diagnosis or therapeutic purposes, X-rays have many applications in medicine. Synchrotron Radiation sources open new perspectives. This has already been the case for a number of years in molecular and cellular biology where the scope of absorption and diffraction work has been greatly extended. This could also be the case for medical imaging and radiotherapy where the characteristics of the beam (collimation, stability, flux) allow new approaches in the energy range of radiological X-rays, namely between 30 keV and 100 keV. Such a source exists today in Grenoble, with the European Synchrotron Radiation Facility (ESRF). The opening of a beamline dedicated to medical research for whole European scientific community is planned for the end of 1996. This beamline, coupled with the "microbeam" beamlines, will cover medical imaging (angiography, tomodensitometry, microtomography, X-ray microscopy) as well as radiotherapy.

Animals↗
PubMed1995

[Value of image guided neurosurgery in neuro-oncology].

Brain tumor surgery, stereotactic or by resection, is based on the precise knowledge of the spatial position of the target and of their relationships with the normal brain structures. Modern computed neuroimaging allows image guidance of neurosurgical procedures, using robots driven by the coordinates of the target and of the entry point. We have developped a stereotactic robot as well as a robotized microscope which are guided from digitized images. They are used in routine daily practice and will become part of the standard neurosurgical equipment.

Brain Mapping↗
PubMed1994

Functional MRI of the human brain: predominance of signals from extracerebral veins.

This study demonstrates the predominance of extracerebral vascular signals in gradient-echo functional magnetic resonance imaging of motor activity at 1.5 Tesla. The demonstration is based upon a novel experimental approach. Maximum intensity projection images are derived from a large set of contiguous 2D functional MR images, and compared with MR angiograms obtained from the volume covered by the set of functional MR images. The comparison shows that the hyperintensities in the functional MR images cover extensive areas, which can be superimposed with a number of veins in the MR angiograms. These results should trigger a general caution in interpretation of the observations in 1.5 Tesla functional MRI.

Brain↗
PubMed1994

Standardisation of 31phosphorus-nuclear magnetic resonance spectroscopy determinations of high energy phosphates in humans.

A procedure is described for standardising the determination of adenosine 5'-triphosphate and phosphocreatine concentration ([ATP] and [PC], respectively, in absolute arbitrary units) in human muscle by nuclear magnetic resonance (NMR) spectroscopy. The individual 31phosphorus (31P)-NMR spectra obtained on equal hemispherical tissue volumes (muscle plus skin and fat) were corrected for the thickness of the skin and of the subcutaneous fat. The volumes investigated were standardised using an external reference. The procedure described made possible the comparison of high energy phosphate concentrations among different subjects. It was applied to the assessment of [ATP] and [PC] in four groups of sedentary subjects (children, and adults aged 20-35, 35-50 and over 50 years), and in a group of athletes (volleyball players). The [ATP] and [PC] were not statistically different in the groups investigated.

Adenosine Triphosphate↗
PubMed1994

Determinants of peak muscle power: effects of age and physical conditioning.

The relationships between absolute peak muscle power (Wpeak), muscle cross sectional area (CSAtot, i.e. the sum of both thigh and calf CSA) and muscle high energy phosphate concentration (adenosine 5'-triphosphate [ATP] and phosphocreatine concentrations [PC]) were studied in 47 subjects classified into five groups: A, 10 sedentary (S) subjects aged 20-35 years; B, 9 S aged 35-50 years; C, 9 S aged more than 50 years; D, 13 children aged 8-13 years; and E, 6 athletes (top level volleyball players) aged 24 (SD 3) years. The Wpeak was measured during a maximal vertical high jump off both feet on a force platform. The CSAtot was measured anthropometrically. The [ATP] and [PC] were determined by 31Phosphorus nuclear magnetic resonance spectroscopy. The Wpeak decreased with age, was 65% lower in D than in A, and 43% higher in E than in A. The CSAtot did not vary with age, was 45% smaller in D than in A, and 15% greater in E than in A. The [ATP] and [PC] were essentially the same in all groups. The changes observed in Wpeak were only partially accounted for by changes in CSAtot. Therefore, in addition to the variables investigated, other factors appear to have been involved in the determination of Wpeak with increasing age and training. An important role may be played by hormonal, particularly at puberty, and neural factors.

Adenosine Triphosphate↗
PubMed1993

Large inferior right hepatic vein. Clinical implications.

The right middle and inferior hepatic vv. are very frequent, indeed constant, but usually of small caliber. The presence of an extra-wide right inferior hepatic v., usually solitary, produces a variation in the venous drainage of the right lobe of the liver. The right inferior hepatic vv. reaching or exceeding a caliber of 0.5 cm were investigated in 125 anatomic liver specimens: 70 injection-corrosion specimens, 32 formolised livers and frontal or frontal-oblique sections of the trunk made in 23 cadavers. The incidence of such vv. was estimated at 9% in the injection-corrosion specimens, 13% in the sections and 16% in the formolised livers. The incidence of these vv. in the literature varies from 10% to 24% according to the method used to demonstrate them. Usually, there is a balance between the right superior and inferior hepatic vv. Rarely, the right inferior hepatic v. predominates compared with the right superior hepatic v. The position of an extra-wide right inferior hepatic v. is constant, close to the visceral aspect of the liver. Its appropriate territory is segment VI, but it may encroach somewhat on adjacent segments. Clinically, the existence of an extrawide right inferior hepatic v. as detected by MRI and, especially, located by intraoperative ultrasonography, allows performance of a subtotal hepatectomy leaving only segment VI. In certain pathologic conditions, thanks to the development of anastomoses between the hepatic vv., an extra-wide right inferior hepatic v. may contribute to a compensatory circulation towards the right atrium.

Hepatectomy↗
PubMed1993

Improved noninvasive diagnostic testing for malignant hyperthermia susceptibility from a combination of metabolites determined in vivo with 31P-magnetic resonance spectroscopy.

BACKGROUND: Phosphorus magnetic resonance spectroscopy (31P-MRS) in vivo has been suggested recently as a possible noninvasive diagnostic test in malignant hyperthermia (MH) susceptibility. However, differences between protocols and also within subjects may have led to inconsistent MRS abnormalities reported during and after exercise. The aim of the current study was to detect discriminant abnormalities in the leg muscles using in vivo 31P-MRS during the rest period. METHODS: Fourteen patients shown to be MH-susceptible and 22 patients MH-negative on the basis of in vitro caffeine/halothane contracture tests according to the European MH group protocol were compared to 36 control subjects using in vivo 31P-MRS during the rest period. A score of MRS combined abnormalities was calculated from a stepwise discriminant function analysis. RESULTS: The MH-susceptible group had a significantly (P < 0.01) higher inorganic phosphate (Pi) to phosphocreatine (PCr) (Pi/PCr) value (0.134 +/- 0.022) than either the MH-negative (0.097 +/- 0.016) or the control (0.101 +/- 0.017) group. The MH-susceptible group also exhibited a significantly (P < 0.01) higher phosphodiesters (PDE) to PCr (PDE/PCr) value (0.093 +/- 0.056) than either the MH-negative (0.034 +/- 0.021) or the control (0.029 +/- 0.019) group. Combining both MRS parameters, 13 of the 14 MH-susceptible patients demonstrated abnormal MRS test results (score value < 1.65). Conversely, 21 of the 22 MH-negative patients had normal MRS results (score value > or = 1.65). The sensitivity and specificity of this threshold value were 93 and 95%, respectively. CONCLUSIONS: This study confirms that 31P-MRS could be useful for distinguishing noninvasively between MH-susceptible and MH-negative patients if several MRS parameter are combined. Moreover, the present MRS approach appears to be more reliable and easier than that used during exercise.

Adolescent↗