L'apport des Potentiels Evoqués chez le patient comateux

L’enregistrement des Potentiels Evoqués (PE), Visuels, Somesthésiques et Auditifs du Tronc Cérébral permet une évaluation des fonctions du cortex et du tronc cérébral et peuvent ainsi fournir des éléments pronostiques déterminants chez les patients comateux. Trois types de facteurs peuvent donner lieu à des altérations des PE chez ces patents : des facteurs extracérébraux (pathologies sensorielles, modifications de la température corporelle, administration de drogues, déprimant l’activité du cerveau), des pathologies à répercussions cérébrales, mais non primitivement cérébrales (insuffisance rénales et hépatiques) et des pathologies primitivement cérébrales (anoxie, hypertension intracrânienne, lésions cérébrales focalisées). Seules les dernières donnent lieu à des altérations influençant réellement le pronostic neurologiques du patient. Deux paramètres essentiels peuvent être extraits des PE : les indices de fonctionnement hémisphérique global et les indices de conduction sous-corticale. Leur caractère normal ou pathologique implique un pronostic favorable ou défavorable si l’examen est pratiqué durant les dix premiers jours ou à partir du premier jour suivant l’accident aigu, respectivement. Les PE présentent un tableau spécifique chez les patients en coma dépassé. Leur enregistrement permet dès lors d’en poser le diagnostic, en complément à l’examen clinique et à l’électroencéphalogramme, même chez les patients chez lesquels ont été administrées des drogues déprimant l’activité du système nerveux. La valeur pronostique des PE dépend, enfin, de leur intégration dans un contexte clinique globalThèse d'agrégation de l'enseignement supérieur (faculté de médecine) -- UCL, 199

How clinical neurophysiology may contribute to the understanding of a psychiatric disease such as schizophrenia.

The increasing knowledge about anatomical structures and cellular processes underlying psychiatric disorders may help bridge the gap between clinical manifestations and basic physiological processes. Accordingly, important insights have been brought these last years into a main psychiatric affection, i.e. schizophrenia.Journal ArticleReviewSCOPUS: sh.jinfo:eu-repo/semantics/publishe

Median nerve somatosensory evoked potentials in profound hypothermia for ascending aorta repair

Median nerve somatosensory evoked potentials (SEPs) were recorded in 9 patients undergoing profound hypothermia for surgical repair of the aortic arch. In addition to the known increase in peak latencies, hypothermia gave rise to the appearance of peaks ('P13,' 'N14') inconsistently recognized at normothermia; moreover, profound hypothermia is associated with the disappearance of cortical activities around 20 degrees, of subcortical waves at lower temperatures. The practical implications of the results are 3-fold: firstly, they suggest that the 'P13' and P14 should both be intracranially generated, at a pre- and postsynaptic level with respect to the cuneate nucleus, respectively; secondly, they show that some discrepancies between previous papers dealing with SEPs and hypothermia can be explained by differences in the choice of the reference; thirdly, they bring some suggestions on a better use of SEPs to monitor patients undergoing aortic arch surgery

The usefulness of the spinal and subcortical components of the posterior tibial nerve SEPs for spinal cord monitoring during aortic coarctation repair

This study examines how the recording of the lumbar and subcortical components of the posterior tibial nerve (PTN) SEPs may usefully replace that of cortical components in situations in which these components cannot be reliably obtained (infants, high concentrations of halogenated gasses). Lumbar, brain-stem, and cortical PTN SEPs were intraoperatively monitored in 7 patients undergoing repair of aortic coarctation under variable isoflurane concentration (up to 1.2%). Four patients were less than 1 year old. Two distinct activities were evidenced at the lumbar level in all of the patients: the dorsal root component (DRC) and the dorsal horn negativity (DHN). The equivalent of the adult P30 (lemniscal positivity; LP) was also present in all of the patients, whatever their age or the concentration of isoflurane. By contrast, the parietal activities were absent intraoperatively in the youngest patients. Spinal-cord ischemia consecutive to aortic cross-clamping gave rise to early DHN changes and later alterations of the LP in the two patients in which it occurred, while the DRC and the peripheral nerve activities remained unchanged. This elective sensitivity of the DHN is likely due to it being dependent on the gray matter of the spinal cord, the basal metabolism of which is greater than that of the white matter and to the situation of the DHN generator in a watershed zone of the spinal cord. This study emphasizes the interest of PTN SEPs for spinal-cord monitoring in vascular surgery and the importance of combining the recording of parietal activities with that of the lumbar spinal components

Syndrome de Guillain-Barré et hypoacousie.

Guillain-Barré's Syndrome and hearing loss. A child presenting Guillain-Barré's syndrome, together with bilateral hearing loss is presented. The incidence of hypoacusis is unknown. The necessity of behavioural audiometry and electrophysiologic testing is stressed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Assessment of olfactory and trigeminal function using chemosensory event-related potentials : Évaluation des fonctions olfactives et trigéminales au moyen des potentiels évoqués chémosensitifs

GOALS: To give an overview on the theoretical and practical applications of chemosensory event-related potentials. METHODS: Chemosensory event-related potentials (ERPs) may be elicited by brief and precisely defined odorous stimuli. Based on the principles of air-dilution olfactometry, a stimulator was developed in the late 1970s, which allows stimulation of the olfactory neuroepithelium and the nasal mucosa with no concomitant mechanical stimulation. Chemosensory ERPs were obtained after stimulation of the olfactory nerve (olfactory ERPs) or the trigeminal nerve (somatosensory or trigeminal ERPs). The characteristics of the stimulator for chemosensory research as well as the variables influencing the responses are discussed in this paper. RESULTS: Implementation and normative data from our department are reported with different clinical examples from otorhinolaryngologic clinic. The bulk of the evoked response consists of a large negative component (often referred to as N1), which occurs between 320 and 450 ms after stimulus onset. This component is followed by a large positive component, often referred to as P2, occurring between 530 and 800 ms after stimulus onset. Absence of olfactory ERPs and presence (even with subtle changes) of somatosensory ERPs is a strong indicator of the presence of an olfactory dysfunction. CONCLUSIONS: This review examines and discusses the methods of chemosensory stimulation as well as the electrophysiological correlates elicited by such stimuli. The clinical applications of chemosensory ERPs in neurology and otorhinolaryngology are outlined