[Needle catheter jejunostomy. An improved technique for enteral feeding (author's transl)]. / Jéjunostomie intramurale á l'aiguille. Technique a minima pour l'alimentation entérale.

The authors have perfected the method of needle catheter jejunostomy introduced in 1973 for enteral feeding. Using the Seldinger technique reduces the risks of leakage, intra-operative haematoma and fistula following removal of the catheter. The operative procedure is described and the preliminary results are reported.

Correlative study between computerized transverse scanning and stereoimpedoencephalography in space-occupying lesions of the brain.

Stereoimpedoencephalography (SIEG) is routinely used by the authors during stereotactic investigations of glial brain tumours prior to stereotactic implantation of isotopes or prior to conventional surgery: the brain tissue impedance is measured along a probe track according to the four electrodes impedance technique. The correlation between the tissue structures and the corresponding impedance values has been studied by comparison with the CATScan data reported on the stereotactic schedules; impedance values are influenced by changes in arterial pCO2 and also by other unknown factors; in order to avoid these uninterpretable changes of the impedance, the recorded values have been normalized with respect to the average impedance along a control track in the normal hemisphere. As a rule, the impedance profile exhibits a "hole" at the site of the pathological processes like tumours as well as surrounding oedema, and the delimitation of the pathological area is very similar to that obtained by the CATScan. There is a good linear correlation between the values of normalized impedance and the x-ray absorption as given by the computer listing of the CATScan. Lastly, statistical values of normalized impedances are determined for the main structures of the brain, showing that the tumour tissue has an impedance equal to half the impedance of the normal tissue.

[Intracranial pressure. IV - Relationships with post capillary vascular pressures (author's transl)]. / La pression intracrânienne. IV - Relation avec les pressions post-capillaires.

The authors have demonstrated experimentally in dogs that, in all cases, the cortical venous pressure (Pvco) is higher than the intracranial pressure (PIC), which always remains higher than the sagittal sinus venous pressure (PSLS). The difference between Pvco and PIC remains statistically equal to 8 mm Hg and can be explained by the "Vascular Waterfall" phenomenon; during Queckenstedt's test, the intracranial venous volume does not change, and is not the cause for the increase of PIC; this increase is due to the constancy of the difference between PIC and PSLS, which is induced by the resorption of CSF through the arachnoïd villi. Increases in Pvco and PIC are shown to be equal to 70% and &2% respectively of the change in PSLS. Any other factor that increases PIC (injections in the cisterna magna, pharmacological effects) does not change PSLS, which remains equal to zero. As long as the cerebral blood flow is constant, the increase in cerebro-vascular resistance of the veins at the site of their junction to the sagittal sinus must be compensated upstream by a vasodilatation, which leads to a new distribution of the pressures along the cerebro-vascular bed.

Electrical impedance brain scanner: principles and preliminary results of simulation.

In previous studies, the authors have shown the importance of impedance recording by stereotactic procedures for brain tumor detection. In this study they report the principles and the first results of an attempt to obtain the impedance value of any given point inside the brain by an external way. The experimental device is mainly made of a set of 128 electrodes, surrounded by an electrode guarding monitored by an operational amplifier the purpose of which is to made the electric field uniform and to enable a focused measure of the impedance by each of the 128 electrodes. The effect of this electrode guarding is demonstrated, and the present sensitivity of the prototype is shown on various obstacles. conductive or non-conductive; the influence of an impedance barrier on this sensitivity is the project of an impedometric scanner is described, and the problems due to the non-linear propagation of electric currents and to the anisotropic properties of the brain tissue are evaluated.

[Delineation of brain tumors by stereo-impedo-encephalography (SIEG) (author's transl)]. / Délimitation des tumeurs cérébrales par stéréo-impedo-encéphalographie (SIEG).

Authors describe the SEEG technique which is routinely used during stereotactic investigations of brain tumors. By the way of the Talairach's stereoencephalographic electrodes, the brain tissue impedance is measured along the probe trajectory with a four electrode impedancemeter (0.25 mA; 5 KHz). The impedance profile provides a good pattern of the brain structures which are crossed; in pathological areas, the impedance significantly decreases as well in gliomas as in edema; cysts and CSF spaces also decrease the recorded impedance. As a contrary, metastases and meningiomas increase the impedance. SEEG appears to be a sharp method for stereotactic delineation of the brain tumors; a larger series as well as the real-imaginary decomposition of the impedance are needed for a best selectivity of the method.

Rheographic assessment of cerebral blood volume and correlations with changes in intracranial pressure.

The authors present a four electrode rheographic technique for simiquantitative continuous measurement of CBV, by examining changes in cerebral tissue impedance induced by changes in blood content of the brain parenchyma. Correlation between the data obtained and ICP measurements permits conclusions regarding the behaviour of the cerebral blood bed. pCO2 regulates CBV, and the phenomenon is reversible according to a hystereris shaped time course in acute experiments. The rebound of ICP after sudden injections of CSF into the cisterna magna is of a vasogenic nature. Changes in CSF volume induce contrary changes in CBV. Pharmacological effects can be studied. The validity of the method is discussed.