Nuclear hemodynamic vertebrobasilar insufficiency. A new approach with the xenon Xe 133 method.

Vertebrobasilar insufficiency is a well-known syndrome, but no corresponding hemodynamic deficit has yet been established. We propose to define nuclear hemodynamic vertebrobasilar insufficiency on the basis of an oligemia lower than 35 mL/100 g per minute in the brain stem-cerebellar region with use of the xenon Xe 133 inhalation method. Fifteen patients fulfilling this criterion underwent four-vessel angiography, computed tomography, and a standardized neurologic examination. An acetazolamide test showed poor reactivity in more than half of the patients, sometimes specifically in the vertebrobasilar area. With use of single-photon emission computed tomography and intravenous technetium Tc 99m-labeled hexamethylpropyleneamineoxime in two cases, the considerable decrease of regional cerebral blood flow in the brain stem-cerebellar region was confirmed. An excellent correlation was observed between the existence of nuclear hemodynamic vertebrobasilar insufficiency and angiographically proved arterial occlusions. The dominant nuclear oligemic zone was regularly on the side of the anatomic arterial chief lesion. Clinical manifestations included rare transient ischemic attacks (in one of 15 patients), intermittent basilar symptoms (in 15 of 15 patients), and a subacute vertebrobasilar "threatening" syndrome. Thus, imaging of a nuclear hemodynamic vertebrobasilar deficit provides an objective basis to the diagnosis of vertebrobasilar insufficiency and useful objective data for revascularization surgery.

A controlled study of Dextran 40: effect on cerebral blood flow and metabolic rates in acute head trauma.

A controlled double-blind evaluation of the effects of Dextran 40 at different concentrations on cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2) and cerebral lactate production (CMRLact) was carried out. We studied 40 patients in coma due to recent head injury. Concentrations of Dextran solution were not significantly related to variations in CBF and metabolic rate over the period of infusion. The lack of effect of the Dextran infusion may be explained by the absence of global brain ischemia in these patients at the time of the study. The very low initial CBF values were a consequence of brain metabolic depression and not a sign of global ischaemia. The rheological benefits of treatment with Dextran 40 in head injured patients should preferably be investigated using techniques which permit detection of local changes in CBF and metabolism.

Assessment of cerebrovascular reactivity by dynamic susceptibility contrast-enhanced MR imaging.

In patients with cerebrovascular disease the acetazolamide (ACZ) test is performed to evaluate the decrease in cerebral perfusion pressure (CPP) through the investigation of the vasomotor reactivity (VMR). This latter is currently assessed with ACZ with several methods. Recently, magnetic resonance imaging (MRI) techniques have been developed that are sensitive to stimulus-induced changes in blood flow. Dynamic susceptibility contrast material-enhanced gradient-echo MRI techniques (DSC-MRI) might be an attractive tool to assess VMR. We aimed to test the ability of DSC-MRI in the assessment of VMR. Relative hemodynamic parameters rCBV, MTT, and rCBF were evaluated at baseline after the first injection of gadopentetate dimeglumine and 10 min after the intravenous administration of ACZ (1 g) with a second bolus of contrast agent. Assessment of hemodynamic parameters was performed over the whole hemisphere and also within regions of interest. The significances of the mean differences, before and after ACZ, were assessed with repeated-measures ANOVA with two within factors: laterality (right-left) and ACZ. DSC-MRI with ACZ test was performed in ten healthy controls (aged 51.4+/-16.2 years). The cerebral hemispheric ratio for the three parameters (cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF)) ranged between 1.01 and 1.03. The mean gray matter-to-white matter ratio for CBV, CBF and MTT were 2.44, 2.41 and 1.05, respectively. As the laterality effect was not significant, left and right hemispheric values were averaged. A significant increase of all hemodynamic parameters was observed after ACZ (P<0.01-0.001). The same changes for CBV, CBF and MTT were observed after ACZ according to the regions of interest (P<0.006-0.015). DSC-MRI is a non-invasive method which enables the assessment of VMR. This technique may be added to any conventional MRI in order to detect a hemodynamic impact of an ICA stenosis. Therefore, it might be useful in determining the appropriate management when the indication for surgical versus medical therapy is in question.

[Amnesic ictus and cerebral blood flow]. / Ictus amnésique et débits sanguins cérébraux.

Cerebral blood flow determinations using the Xenon inhalation test in two patients with transient global amnesia showed overall decreases during the attack with a more marked fall in temporal-inferior frontal flow in one case and in temporal flow in the other. In the latter patient the temporal anomaly was reversible after naloxone injection but clinical improvement was lacking. Blood flow determinations in a further patient with transient global amnesia, after 2 mg of ergotamine tartrate plus caffeine, showed a global decline in flow without focal anomaly, with recovery after ten days. Values obtained in two other patients 24 and 38 hours respectively after typical transient global amnesia attacks were normal. The effect of naloxone appears related to a direct neuronal action although the role of endorphins in this affection is not conclusive. Comparison of these anomalies with those noted by Reichle with position emission tomography imaging suggests a primary neuronal mechanism.

Onchocerciasis in West Africa after 2002: a challenge to take up.

Initially planned for a 20 year life time, the Onchocerciasis Control Programme in West Africa (OCP) will have finally continued its activities for nearly three decades (vector control alone from 1975 to 1989, then vector control and/or therapeutic treatment until 2002). Although onchocerciasis is no longer a problem of public health importance nor an obstacle to socio-economic development in the OCP area, the control of this filariasis is not over because OCP never aimed at eradication, neither of the parasite (Onchocerca volvulus), nor of its vector (Simulium damnosum s.l.). In 2003, the eleven Participating countries of OCP will take over the responsibility of carrying out the residual activities of monitoring and the control of this disease. This mission is of great importance because any recrudescence of the transmission could lead in the long run to the reappearance of the clinical signs of onchocerciasis, if not its most serious manifestations. For epidemiological and operational reasons, and given the disparity in national health policies and infrastructures, the capacities of the countries to take over the residual activities of monitoring and control of onchocerciasis are very unequal. Indeed, the interventions to be carried out are very different from one country to another and the process of integrating the residual activities into the national health systems is not taking place at the same pace. This inequality among the countries vis-a-vis the challenges to be met does not, however, prejudge the epidemiological situation after 2002 whose evolution will also depend on the effectiveness of the provisions made before that date by OCP, then after 2002, by the Regional Office for Africa of the World Health Organization which is currently setting up a sub-regional multidisease surveillance centre.

[Dosimetry and bone densitometry: examples of LUNAR IQ and HOLOGIC 4500A]. / Doses et ostéodensitométries: exemple du LUNAR IQ et de l'HOLOGIC 4500 A.

Patient dosimetry related to two bone densitometer units from different manufacturers (LUNAR IQ and HOLOGIC 4500A) were evaluated using the parallel beam technique and thermoluminescence from Ca (SO4)/Dy. The radiation dose measured for a phantom of 18 cm in thickness was 0,11 mGy (+/- 0,004) at a maximum current of 3 mA for the LUNAR IQ unit in the high-resolution mode. The radiation dose is 0,28 mGy (+/- 0,011) for the HOLOGIC 4500A unit used at 2,5 mA in the high resolution-mode. These results obtained by thermoluminescence of the Ca (SO4)/Dy are in favor of the LUNAR IQ unit. However, dosimetry must be weighted against image quality.

[Experimental study of the relative biological effectiveness (R.B.E.) of a fast neutron beam (author's transl)]. / Etude expérimentale de l'efficacité biologique relative (E.B.R.) d'un faisceau de neutrons rapides.

A preliminary experimentation has been done with the synchrocyclotron (28 MeV deuton) in Lyon. The different characteristics of the beam have been determined through various dosimetric measurements. C57Bl mice have been irradiated with single doses and fractionated schedules (5 sessions). 7 day survival has been analysed. Comparison of neutron and cobalt gamma ray shows a R.B.E. of 1.95 for single dose and 2.5 for five fractions. This work is a confirmation of the effect of fractionation on the R.B.E. of the neutrons.

[rC.B.F. measurements by a gamma camera and the 133 Xe inhalation technique. Interest of a local partition coefficient tissue-blood (author's transl)]. / Débits sanguins cérébraux régionaux mesurés avec une gamma-caméra et selon la méthode d'inhalation du Xénon 133. Intérêt due coefficient de partition tissus-sang régional dans les A.V.C.

More than 400 patients who had undergone a cerebrovascular attack or a transitory ischemic attack had bilateral measurements of regional C.B.F. by the 133 Xe inhalation technique and a gamma-camera. Inhalation of the air-Xe mixture in the closed spirometric circuit takes 1.5 mn at a concentration of 1 to 2 mCi/1. A very high resolution collimator allows a maximal counting rate of 300 000 i.p.m per hemisphere. At the opening of the circuit, the cerebral curves are analysed by the initial slope index (ISI) method, that index being obtained by deconvolution of the first 2.5 minutes of wash out. With this method, normal values are: 44,5 +/- 5ml/mn/100g. After calculation of hemispheric and regional ISI, we evaluate a regional partition coefficient (for total hemisphére) between tissue and blood with this formula: Formula: [See Text], being the activities counted at time t respectively in the area and on the hemisphere. Koh and Kor referring to ISI in total hemisphere (H) and area (r) C (a): arterial concentration A regional blood flow is obtained by Fr = 100 lambda rKor in a maximum of 16 different areas (with lambda n = 1ml/g) With our data processing system we get a functional image of r CBF which visualizes values of the (lambda r. Kor). In order to avoid statistical problems due to separate calculations of lambda r and Kor in very small areas we use a very simple kind of a functional image: subtraction of regional cerebral activity between time 0.5 and 1.5 mn and at 1.5 and 2.5 mn of wash out. We show that this image is correct display of regional inequalities of lambda rKor. In 48 cases of complete stroke comparison of the ISI index Kor and the ISI index Kor and the lambda r Kor referring to the area of maximal ischemia appearing on the functional image showed perfect correlation between the lambda rKor and the functional image; and only in 80% cases with the unique value of Kor. Those discrepancies between Kor and lambda rKor are related to necrosis and late revascularisation in cerebro vascular attacks.

[Variations of the cerebral blood flow after hyperbaric oxygenation in traumatic coma]. / Etude des variations de débit sanguin cérébral après oxygénation hyperbare dans le coma traumatique

We have previously shown (Ref. I) the absence of variations in average cerebral blood flow, measured by the method of LASSEN, following treatment of traumatic coma by means of hyperbaric oxygenation patients presenting with brainstem contusion, during 2 hours of HBO (at 2.5 times atmospheric pressure) measurements of cerebral blood flow were made using a single detecting probe, before and two hours after terminating HBO. Measurements in 9 patients demonstrated variations in cerebral flow greater than predicted by experimental error (+/- 4%): 5 measurements (these with initial flow less than 31 ml/mn/100 g increased following OHB, while 4 measurements (these with initial flow greater than 31 ml/mn/100 g) decreased following OHB. In order to determine the significance of these variations, we studied the correlation between two methods of calculating cerebral blood flow : the exponential (bicompartimental) method, and the stochastic method, assuming lambda the coefficient of partition, tobe equal to I. These two method of calculation appear to be independant ; thus, the observed correlation (r = 0.74, p less than 0.01) tends to validite the measured variations in flow. This finding is further supported by the calculated correlation between the change in flow as measured by the exponential and that measured by the stochastic method (r = 0.684, p less than 0.05). Thus, we feel that measured changes in flow represent changes in cerebral perfusion, and cannot be attributed to the method of calculation. The bio exponential method of calculation of flow, D = Dg + Dw (with Dg = fg. Wg = "index of grey perfusion" and Dw = fw. Ww = "index of white perfusion", where fg = lambda1. (see article), and where Wg and Ww represent the percentage of the grey and white substance) permit calculation of a highly significant correlation between the change in flow and the grey perfusion index (r = 0.83, p less than 0.01). This correlation, previously described in the literature, appears to explain the observed findings in terms of the variations in perfusion of the grey compartment. However, there exists an equally significant correlation, but negative, between the variations of the grey and white perfusion index (r = 0.824, p less than 0.01). This correlation seems to indicate the presence of an inverse relationship between flow to grey and white substances, tending to minimize the variations of the total flow after OHB. We can then formulate an explanatory hypothesis: if one assumes that the diminution of intracranial pressure during OHB, by decreasing cerebral edema, hastens the recovery of perfusion in the damaged zones, then the response to therapy with hyperbaric oxygenation should differ, depending on whether the tissues were healthy or damaged. Healthy tissues should show a decrease, while damaged zones should show an increase in flow following OHB. This mechanism would appear to explain, in relation to lesions located predominantly in grey or white matter, the observed negative correlation between blood flow to the two compartments.

[Control of vectors of human onchocerciasis in intertropical Africa (author's transl)]. / La lutte contre les vecteurs d'onchocercose humaine en Afrique intertropicale.

First the authors make short comments on the two Simuliidae species complexes vectors of African human onchocerciasis (S. damnosum s.l. and S. neavei), as well as on the reasons for renewed interest in the control of those vectors; then they review the various possible methods of control (ecological, biological, genetical and chemical methods) and they finally detail the methodology of anti-S. damnosum chemical larviciding which is the only kind or large scale control presently used against onchocerciasis vectors. The experiences and results of the previous campaigns resulted in the large Onchocerciasis Control Programme in Volta River Basin (O.C.P.) which now appears as a model for present and future control measures against S. damnosum. This Programme is briefly described, together with its results, problems (reinvasion) and orientations. As a conclusion, the excellent level of control of the vectors and onchocerciasis transmission which is obtained is emphasized and it is expected that in the future new large scale campaigns using O.C.P. experience may be initiated.

[Hemodynamic vertebrobasilar insufficiency demonstrated by chronic oligemic cerebral flow and cerebellar ataxia: two new concepts]. / Insuffisance vertébro-basilaire hémodynamique démontrée par les débits cérébraux et ataxie cérébelleuse oligémique chronique: deux nouveaux concepts.

We propose in the paper of the concept of nuclear hemodynamic vertebrobasilar insufficiency, defined as an oligemic blood flow lower than 35 ml/100 g/min. in the brain stem-cerebellum zone, when using the method of inhalation of 133Xe. In 15 patients, the neurophysiologic manifestations included intermittent symptoms. We describe here permanent neurophysiologic motor disturbances: extrapyramidal Dopa sensitive syndrome (2/15), chronic cerebellar ataxia (12/15), often associated with cerebellar atrophy (8/12). The concept of chronic oligemic cerebellar ataxia, corresponding to selective neuronal death and/or neurochemical failure, is proposed.

rCBF landscapes during motor performance and motor ideation of a graphic gesture.

The regional cerebral blood flow (rCBF) distribution was measured by 133xenon inhalation using a gamma camera in 18 right-handed volunteers, 6 subjects performing a graphic task (writing numbers in letters) with the right hand, 6 subjects imagining the same task, and 6 subjects were assessed during two rest periods to determine the reproducibility of the technique. The mean rCBF increased between 10% and 25% (P less than 0.01) during both motor performance and motor ideation. However, there were regional differences. While motor performance activated mainly the rolandic regions bilaterally, motor ideation gave prefrontal and premotor rCBF augmentations. In both situations there was significant bilateral increase in regions corresponding to the cerebellum.

[Evaluation of pelvic irradiation during x-ray computed tomography]. / Evaluation de l'irradiation pelvienne au cours des examens tomodensitométriques.

Accidental irradiation of an early and unknown pregnancy during abdomino-pelvic computed tomography has not yet been reported, but this situation will certainly occur as the indications for this type of investigation are extended. Assessment of foetal risk depends essentially, as in ordinary radiology, upon the X-ray dose received by the foetus. Only a few studies have been devoted to determination of the "gonad dose" received during an abdomino-pelvic scan. In ten patients undergoing abdomino-pelvic scan with a mean of 22.1 +/- 4.7 exposures per patient, the authors used a small thermoluminescent dose-meter placed in the uterus or endocervix to measure the gonad dose received. The dose delivered to the uterus was 1.67 cGy +/- 1.14 per patient, i.e. approximately the same as for hysterography (1.27 cGy). Thus any abdomino-pelvic scan before twelve weeks should be viewed as an indication for therapeutic abortion, whilst after twelve weeks the amount of radiation received does not in itself represent an indication for abortion.

[Nicergoline and steal effect in favor of zones of hypoperfusion in cerebral ischemic accidents]. / Nicergoline et hémodétournement en faveur des zones d'hypodébit dans les accidents ischémiques cérébraux.

Hemispheric and regional variations of cerebral blood flow (CBF) were studied with the Xenon inhalation technique on 19 patients suffering from cerebral infarcts before and at the end of a 10 mg 'alpha-blocking' Nicergoline perfusion. CBF dynamic images and calculations were performed with a gamma computerized camera. No significant hemispheric CBF modification has been noted after Nicergoline perfusion (30.2 +/- 4.5 ml/min/100 g before perfusion and 31 +/- 5.6 ml/min/100 g at the end of perfusion) but, at the end of perfusion, we noticed a CBF increase on the more ischemic areas (25.7 +/- 5.6 ml/min/100 g before and 29.9 +/- 6.8 ml/min/100 g after). This variation depends on the patients (from +67% to -22%). The more ischemic areas are those with the more important CBF increase. This 'inverse steel effect' is comparable to the effect described by other authors for Vincamine or Piracetam.

[Correlation between the number of microfilaria ingested and the thickness of the peritrophic membrane of the vector in onchocercosis of the African savannah]. / Corrélation entre le nombre de microfilaires ingérées et l'épaisseur de la membrane péritrophique de vecteur dans l'Onchocercose de savane africaine

The fact, as previously established, that a great number of microfilariae remain trapped in the peritrophic membrane of S. damnosum, explains the low proportion of microfilariae passing into the hemocoel. However, it doesn't account for the strong "limitation phenomenon" observed in savannah. Histological analysis shows a growth of the peritrophic membrane proportionate to the number of ingested microfilariae. The microfilariae, exciting the digestive epithelium, provoke the liberation of greater quantities of peritrophic substance, thus reinforcing the peritrophic barrier.