Le paradigme « oddball » dans les modifications des états de vigilance et de conscience

info:eu-repo/semantics/nonPublishe

Subdural motor cortex stimulation: feasibility, efficacy and security on a series of 18 consecutive cases with a follow-up of at least 3 years.

Motor cortex stimulation (MCS) is considered to be an effective treatment in some types of chronic refractory neuropathic pain. The aim of this study is to evaluate and confirm the feasibility, efficacy and security of our surgical technique for subdural motor cortex stimulation (SD MCS) on 18 consecutive cases with follow-up of at least 3 years

The use of alpha 2 agonists during idiopathic scoliosis repair: A narrative review of the literature

Alpha 2 agonists are appreciated drugs designed for the peri-operative period, because of their anxiolytic, sedative and analgesic properties. However, they are usually avoided during scoliosis surgery, a longlasting major procedure involving healthy patients, because of their potential effects on Somatosensory and Motorevoked potentials. The absence of recommendations suggests that their effects on evoked potentials are still unclear. Thus, we tried in this narrative review to identify the literature representative of the effects of Clonidine and dexmedetomidine on evoked potentials, on human beings, published between 1988 and 2015 in English or French, using GOOGLE SCHOLAR and PUBMED. Paucity of literature prevented any conclusion about Clonidine's effects on evoked potentials, but no data suggested a noxious effect of Clonidine on evoked potentials, used in oral premedication (300 μg) or during the procedure (2 to 5μg/kg). If literature was more extensive for dexmedetomidine, studies were still controversial. Although the majority of the studies did not find statistically significant differences concerning the effects of this drug on evoked potentials (loading dose of 0.3 to 1 μg/kg followed by continuous infusion of 0.3 to 0.8μg/kg/h), 2 case reports and 2 studies described substantial decreases. However, dexmedetomidine's shorter duration of action allowed a quick return to basal situation within an hour. In conclusion, more studies are needed in order to evaluate the effects of alpha 2 agonists on evoked potentials and to assess the safety of their use in this setting

Deep EEG recordings of the mammillary body in epilepsy patients.

PURPOSE: To our knowledge, the epileptic and nonepileptic electroencephalographic (EEG) discharges recorded within the human mammillary body (MB) and mammillothalamic tract (MTT) areas have never been published. Herein, we present the EEG recordings from these structures in patients with refractory epilepsy (RE). METHODS: Three men (ages 41-43 years) were enrolled in a clinical trial for deep brain stimulation (DBS) of MB-MTT in RE. Previous evaluations had demonstrated a low likelihood of successful response to medication or resective surgery. DBS macroelectrodes were bilaterally implanted within the MB-MTT under general anesthesia and their location checked by magnetic resonance imaging (MRI). We obtained a surface-depth EEG for a 2- to 4-day period, including monitoring of the cardiorespiratory and mnemonic functions. RESULTS: The background pattern of EEG recorded from MB-MTT was low-amplitude (usually <25 microv for MB and <20 microv for MTT) waves with a variable combination of theta-beta rhythms. In two patients, pseudoperiodic slow spikes were unilaterally recorded with or without clinical signs. For one patient, several focal ictal discharges were recorded in the right MB without scalp EEG changes. CONCLUSIONS: The analysis of our depth EEG revealed that the theta-beta pattern represents the predominant physiologic profile of MB. Paroxysmal epileptiform discharges can be observed in human MB. These data supplement those available from animal observations

Le suivi par potentiels évoqués somesthésiques des patients adultes subissant un arrêt circulatoire sous hypothermie profonde.

The surgical repair of ascending aorta aneurysms can only be carried out under total circulatory arrest, and is consequently to be performed under deep hypothermia, in order to adequately decrease the metabolic requirements of the brain. However, the optimal temperature to be reached is poorly known. SEPs to median nerve stimulation were recorded in 21 operations performed in 20 patients undergoing profound hypothermia. The latencies of all SEP components increase to 21 degrees C. Waves N20 and P14 disappear at mean naso-pharyngeal temperatures of 20 degrees C and 17 degrees C, respectively, although a wide inter-individual variability was observed. We suggest to use the P14 disappearance as the criterion to perform the circulatory arrest: in fact, all surviving patients in whom this criterion was fulfilled recovered without any detectable neurological sequellae, while three patients in whom brain activities disappeared independently on body temperature presented with neurological sequellae. Moreover, particularly if patients presenting with ischemia-induced disappearance of Erb's point activities were excluded, we found a significant correlation between the duration of the circulatory arrest and the delay of N20 and P14 reappearance on rewarming. This confirms the importance of sufficient hypothermia, on the one hand; and on the other hand, our findings imply that, even if SEP monitoring considerably decreases the risk of neurological sequellae associated with these operations, the duration of the circulatory arrest should be reduced as far as possible

Brain death diagnosis in misleading conditions.

The necessity of defining brain death (BD) arose from technological development in medical science. The definition of this concept had practical consequences and opened the way to organ donation from BD patients. Nowadays, the imbalance between the number of organs available for transplantation and the size of the demand is becoming critical. In most laboratories, a BD diagnosis is made according to precise criteria and in a well-defined process. BD diagnosis should be improved, not only to assure the safety and to preserve the human dignity of the patient, but also in order to increase the rate of organ donation. By analysing some epidemiological parameters in BD diagnosis and organ donation, it appears that BD diagnoses can be made more often and more rapidly if one has a reliable, accurate, and safe confirmatory test, especially under misleading conditions (hypothermia, drugs, metabolic disturbances). In our experience, the use of multimodality evoked potentials (MEPs) to confirm a BD diagnosis has many advantages: MEPs can be rapidly performed at the patient's bedside, assess the brain stem as well as the cerebral cortex, and are innocuous for the patient. Moreover, their insensitivity to the aforementioned misleading factors is sufficient to distinguish BD from clinical and EEG states that mimic BD. They give an immediate diagnosis, and no delay is required in BD confirmation if there is sufficient cause to account for BD. MEPs are a safe, accurate, and reliable tool for confirming a BD diagnosis, and their use can improve the organ donation rate while preserving the safety of the patient