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F Cohadon

Publications and source records attributed to F Cohadon.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Training of surgeons for laboratory research].

A degree in surgical research has been set up in 1986 in France. It includes a one-year full time work in a research laboratory, and seminars (one to three days long, each). General surgical research objectives are gathered in a first seminar. Then, candidates select one among four optional subjects: biomaterials-artificial organs, transplantation, oncology, and neurosciences. Two prerequisites are necessary in order to register. The first is to write a research project according to standardized rules, and the second is to attend two seminars, one dealing with scientific communication and the other with methodology in clinical research. A nation-wide valid Academic degree is delivered to candidates who pass an oral presentation of their research report and who attended all seminars according to the optional subject that they selected. From 1986 to 1993, 434 students attended the formation. They came from different regions of France, proving the nation-wide characteristic of the degree, and some from foreign countries. Seminars were held in different French University towns. An increasing number of students become Ph.D.

Education, Medical, Graduate↗
PubMed1994

[Stereotaxic biopsies of pineal tumors. Comments on their risk and implication apropos of 370 cases].

370 stereotactic biopsies of pineal region tumors, from 15 neurosurgical centers in France have been reviewed with the goal to evaluate the mortality/morbidity rates and diagnostic yield of this procedure. The impact of neuroradiological means of localisation, the probe trajectory, the type of biopsy instrument, the time of shunting are discussed in order to maximize the diagnostic yield and minimize the mortality/morbidity rates. Stereotactic biopsy contribution, as compared to other diagnostic methods, in pineal region tumors was evaluated. The mortality rate was 1.3 % (5 patients of 370), 3 patients suffered severe neurological complication. In relation to the large number of patients in this study, we can assess that the mortality rate of stereotactic biopsy in this region doesn't significantly exceed that of stereotactic brain tumor biopsies in general.

Adolescent↗
PubMed1993

[Deep cerebral stimulation in patients with post-traumatic vegetative state. 25 cases].

In 25 cases of post traumatic vegetative state persisting 3 months after the initial injury, deep brain stimulation (DBS) has been used with the aim to activate the cortex and the hope to produce some degree of functional recovery. Electrodes were stereotaxically implanted in the centrum medianum-parafascicularis complex. Bipolar stimulation was provided daily from 8 a.m. to 8 p.m. In 12 cases no changes occurred in the clinical features and overall behaviour. DBS was given up after 2 months. All these patients with a follow-up of 1 to 10 years, remained in a permanent vegetative state, 4 of them eventually deceased. In 13 cases, following 1 to 3 weeks of DBS a definite improvement was obtained with recovery of some degree of consciousness and interpersonal relationship. However all these patients, with 1 to 12 years follow-up remained severely disabled. 2 of them deceased from intercurrent causes. The practical meaning of these clinical results are questioned. We consider that the absence of response to DBS is an important argument to predict the irreversibility of post traumatic vegetative state. It is not certain that DBS is directly responsible for positive changes observed, some degree of long-term spontaneous recovery being already documented in such patients. However it seems likely that DBS accelerates recovery and possibly improves the final level of performances.

Brain Injuries↗
PubMed1993

[Electrophysiological development under thalamic stimulation of post-traumatic persistent vegetative states. Apropos of 25 cases].

We have studied the electrophysiological evolution, with the aid of long-term, quantitative E.E.G. (Holter method) and sensory evoked potentials (visual, auditory and somatosensory) on 25 severe traumatic head injury patients (initial Glasgow scale--between 3 and 5) aged from 5 to 42 years having evolved towards a persistent vegetative state and being object of a protocol of thalamic stimulation. Electrophysiological exploration was practised before placement of the stimulation, then at 2 weeks, 1 month, 2 months and finally 3 months after. The electrophysiological parameters appear to have no predictive value on the clinical evolution after stimulation. However, changes such as long-term quantitative EEG as well as evoked potentials mostly precede clinical progress when present. Cortical evoked potentials are the first to change significantly (J15) followed by long-term quantitative EEG and brain stem evoked potentials (J30); the latter improving more completely. Also the consideration of the chronobiological aspects of the recordings of the long term EEG allow the proposal of "waking targeted" stimulations at the most favorable moments of the nyctohemeral period.

Adolescent↗
PubMed1992

A longitudinal assessment of seizure outcome and overall benefit from 100 cortectomies for epilepsy.

Results of 100 cortical resections for 76 temporal, 23 frontal and one parietal lobe epilepsies were studied in terms of seizure relief and overall benefit. A non-homogenous Markov chain model was used to take into account both the intravariability of post-surgical outcome and the differences in duration of follow-up in a group of patients consecutively operated. The seizure free (SF) state was defined as no seizure in the previous five months at first follow up visit and none in the preceding 12 months at subsequent annual visits. For the whole of the population the SF probability was 82%, 66%, 61%, and 62% at six months, one year, two and five years respectively. A better outcome was found for temporal lobe epilepsy (SF probability: 68% at the fifth postoperative year) than for frontal lobe epilepsy (SF probability: 42% at the fifth postoperative year) with a statistically significant difference. Pre- and postoperative interictal signs and symptoms were classified according to their clinical significance: (a) mild handicap--symptoms recognisable but no interference with usual life, and (b) moderate or severe handicap--interference with some or all daily activities. The interictal state was considered more impaired after surgery than before in two situations: (a) either symptoms, absent before surgery, appeared in the postoperative period involving a moderate or severe handicap, or (b) symptoms present before surgery and answerable for a mild or moderate handicap that increased to involve a moderate or severe handicap respectively in the postoperative period. Surgery was considered a major benefit when two conditions were fulfilled-namely, a SF state and no deterioration of the interictal stage when compared with the preoperative period. The probability of obtaining such a benefit was 58%, 51%, 48% and 56% at six months, one year, two and five years respectively. The results suggest that surgery is an effective treatment for more than 50% of long lasting medically intractable epilepsies.

Adolescent↗
PubMed1991

Calcium-activated neutral protease activities in brain trauma.

This paper investigates the level of cytosolic and synaptosomal forms of calcium activated neutral protease activities in the normal brain and their changes following a freezing lesion in the rabbit. From 1 to 24 hours post lesion we observe a progressive disappearing of the enzyme activities from the cytosolic compartment and concurrently their increase in the membranal fraction. These changes are likely to be due to a rise in intracellular calcium concentration, a well documented consequence of many cellular insults. The specific role of the activation of calpain activities in the pathophysiology of trauma is discussed, an enhancement of excitotoxic mechanisms is proposed.

Animals↗
PubMed1991

[Pleomorphic xanthoastrocytoma. Apropos of 3 new cases. Review of the literature].

Three cases of pleomorphic xanthoastrocytomas (P.X.A.), a low grade leptomeningeal glioma are reported. Prominent histological features used for diagnosis were a cellular pleomorphism of G.F.A.P. positive cells, with intracytoplasmic lipidic vacuols. A reticulinic network and mononuclear cells infiltrates have been observed. A weak mitotic activity and lack of necrosis and of endothelial cells proliferation were significant additional features necessary for diagnosis. Our cases were observed during the surgical management of young patients with resistant epilepsy. Neuroradiological examinations showed a tumor superficially located within the temporal or the parietal lobe. This tumor could be calcified and/or cystic. Operative aspects showed a firm and non-encapsulated leptomeningeal tumor with possible various colors. Our patients were seizures-free after surgery even during the follow-up. From the currently reported cases clinical follow-up ranging for 1.5 to 3 years is not sufficient to predict a favorable carcinologic prognosis. P.X.A. is an uncommon tumor and less than 50 cases are reported throughout the literature. This tumor affecting young subjects mainly during the second decade is revealed in the majority of cases (3/4) by epileptic seizures, less frequently by a deficit or by an intracranial hypertension. The great majority of clinical events are observed before 20 years. The functional prognosis is rather good after surgery with a disappearance of epileptic fits in about 50% of the cases. Throughout the literature the prognosis of this tumor seems to be comparable to low-grade astrocytomas. Optimal management of P.X.A. seems to be primary surgical resection with later surgery for residual or recurrent tumor. The role of radiotherapy in the management of P.X.A. is at this time uncertain.

Adult↗
PubMed1990

Thiobarbituric acid-reactive material content and enzymatic protection against peroxidative damage during the course of cryogenic rabbit brain edema.

The relationship between free radicals reactions and the cell detoxifying system was investigated during the development of brain edema following a cryogenic lesion in the rabbit cerebral cortex. The amount of TBA-reactive material present six hours after freezing was less than in the controls, then increased at 48 and 96 hours. The activity of superoxide dismutase (SOD) decreased 6 hours post-injury; at the same time, we observed a stimulation of catalase activity. The glutathione peroxidase activity (GSH-Px) rose 96 hours post-lesion. The decrease of TBA-reactive products could result from an elimination rate that exceeds generation.

Animals↗
PubMed1990

Relation between epileptic activities and edema formation after cryogenic injury in the rabbit.

Although cryogenic lesions have been widely used as experimental models of either focal epilepsy or focal BE, the relation between these two disorders has never been discussed. In these experiments EA and gray matter edema were correlatively investigated during the early phase (1 to 23 hr) after a cryogenic lesion in the rabbit. Indexes were developed to allow a quantitative assessment of EA. The indexes demonstrated that the early phase of cryogenic epilepsy is a rapid phenomenon during the first 4-hr postlesion. Epileptic activity precedes BE, and in individual animals, there is a significant positive correlation between the total amount of EA and edema. EA and BE are most likely interrelated at the level of pathophysiological mechanisms. Excitotoxins and ions would be possible candidates mediating both phenomena.

Animals↗
PubMed1989

Assessment of the experimental model of transplanted C6 glioblastoma in Wistar rats.

Establishing in vivo glioblastoma models from cell lines requires a very strict methodology, in order to obtain reproducible tumors presenting all the characteristics of human spontaneous glioblastomas. In this respect, we have developed a model of glioblastoma in Wistar rats by stereotaxic intracerebral transplantation of a 10 microliters suspension of 6 x 10(6) C6 cells grown in vitro. The tumor take was very high in these conditions, only 1 rat over 30 had no tumor. The median survival time varied from 14 to 20 days. The growth curve of the tumor has revealed an exponential growth up to the 10th day after transplantation with a doubling time of 36 h. Histological examination of the tumors has shown several characteristic features of spontaneous glioblastomas, such as neovasculature, parenchymal invasion, nuclear pleiomorphism, and presence of hemorrhagic and necrotic areas. This C6 model is closer to the usual histological characteristics of spontaneous glioblastomas when using the Wistar rather than other strain, and it should be used in that way for preclinical therapeutic evaluation of new drugs or drug combinations in glioblastoma.

Animals↗
PubMed1989

Membrane damage in acute brain trauma.

Among a number of biochemical disturbances occurring in the acute phase of brain insults, the destruction of membrane phospholipids and its consequences on the function of membrane-bound proteins is likely to be one of the most important. In the cryogenic type of injury which is classically considered as a relevant animal model of brain contusive lesions in human traumatology, the initial attack of membranes could consist in a peroxidative damage triggered by blood ferrous compounds. This in turn would lead to an activation of phospholipase A2. As a consequence of phospholipid disruption a number of enzymes involved in energy production within the mitochondria are severely impaired. Nevertheless, the level of available ATP within the cell remains normal and even higher than normal. This paradoxical findings suggests that energy utilization is even more lowered than energy production. In fact, the Na+-K+-ATPase activity which normally utilizes approximately 70% of the total amount of cellular energy is severely reduced. We assume that Na+-K+-ATPase impairment is directly responsible for the retention of intracellular Na+ accompanied by osmotically driven water, though admittedly other biochemical disturbances, including tissue acidosis and liberation of excitatory amino-acids, would contribute to the same result. Lastly, a striking feature of these biochemical events is the early activation of those enzymes necessary for phospholipid resynthesis. This should mean that repair processes are at work immediately after the insult allowing resumption of Na+-K+-ATPase function, clearing up of brain edema and restoration of cation exchanges essential for brain work.

Animals↗
PubMed1989

[Meningioma of the lateral ventricle. 3 recent cases].

Three recent cases of intra-ventricular meningiomas are reported. The incidence of this tumor type is very low, since they account for only 0.2% of all intra-cranial neoplasms and 2% of all intra-cranial meningiomas in the adult. In our first 2 cases, the meningioma involved the right trigonal area. In our third patient, a 14 year-old girl, the tumor had involved the left occipital horn. It is usually assumed that their development is a result of meningothelial inclusion bodies normally present in the arachnoid of the tela choroidea. As mentioned in previous reports, their clinical presentation may be that of paroxysmal increased intra-cranial pressure and a mechanism of trapped ventricular horn has been advocated. However, under such circumstances, an intraventricular bleeding seems to be a more likely mechanism. Despite their rarety, intra-ventricular meningiomas are usually diagnosed on C.T. It typically shows a hyperdense mass, attached to the plexus and enhancing after contrast infusion. In one of our patients (obs. 2), the meningioma manifested on M.N.R. by a low signal intensity in T1 sequences and by a high signal in T2 sequences. In our third patient, the M.N.R. findings were indicative of a cystic lesion lying in the occipital horn, but not of a meningioma, the diagnosis of which was made on further microscopic examination. The angiographic evaluation remains useful to document preoperatively the arterial supply to the meningioma, which is mainly from the postero-lateral choroïdal arteries. At operation, anterior meningiomas lying near the foramen of Monro are easily exposed through a transfrontal approach and raise no technical problem.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Radiotherapy and cerebral stereotaxis. Examples of dosimetry with 3D reconstruction].

External stereotactic radiotherapy allows to irradiate a small and carefully delimited intracranial volume according to the spatial definition of the target. To determine the distribution of the dose in the volume irradiated, we developed a dosimetric programme adapted to our particular treatment conditions (arc therapy in the frontal and oblique planes converging onto the centre of the target volume with circular beams 8 to 20 mm in diameter using 18 MV X photons). The principle of the programme is a 3D reconstruction based on ten transverse CT slices. This reconstruction, related to the stereotactic coordinates defined during stereotactic localization, visualises the outline of each oblique frontal treatment plane and the outline of the three perpendicular reference planes passing through the centre of the target volume (i.e. transverse, sagittal, coronal). The isodose distribution is then calculated in the planes defined by these reconstructions. Under treatment conditions, we use the parameters measured for each beam with their additional collimation. We present an evaluation of this software performed on a phantom consisting of a skull containing a defined target.

Humans↗