Dysfunction of GABAA receptor glycolysis-dependent modulation in human partial epilepsy.

A reduction in GABAergic neurotransmission has been put forward as a pathophysiological mechanism for human epilepsy. However, in slices of human epileptogenic neocortex, GABAergic inhibition can be clearly demonstrated. In this article we present data showing an increase in the functional lability of GABAergic inhibition in epileptogenic tissue compared with nonepileptogenic human tissue. We have previously shown that the glycolytic enzyme GAPDH is the kinase involved in the glycolysis-dependent endogenous phosphorylation of the alpha1-subunit of GABA(A) receptor, a mechanism necessary for maintaining GABA(A) function. In human epileptogenic cortex obtained during curative surgery of patients with partial seizures, we demonstrate an intrinsic deficiency of GABA(A) receptor endogenous phosphorylation resulting in an increased lability of GABAergic currents in neurons isolated from this tissue when compared with neurons from nonepileptogenic human tissue. This feature was not related to a reduction in the number of GABA(A) receptor alpha1-subunits in the epileptogenic tissue as measured by [(3)H]flunitrazepam photoaffinity labeling. Maintaining the receptor in a phosphorylated state either by favoring the endogenous phosphorylation or by inhibiting a membrane-associated phosphatase is needed to sustain GABA(A) receptor responses in epileptogenic cortex. The increased functional lability induced by the deficiency in phosphorylation can account for transient GABAergic disinhibition favoring seizure initiation and propagation. These findings imply new therapeutic approaches and suggest a functional link to the regional cerebral glucose hypometabolism observed in patients with partial epilepsy, because the dysfunctional GABAergic mechanism depends on the locally produced glycolytic ATP.

Subjective signs in premotor epilepsy: confirmation by stereo-electroencephalography.

Subjective manifestations inaugurating frontal seizures are less well known than those observed in temporal seizures. We report eleven consecutive patients who underwent surgery for premotor epilepsy. Six of them had focal cortical dysplasia. Ictal symptomatology was analysed to establish electroclinical correlations. The localisation of the epileptogenic zone was assessed by stereoelectroencephalographic studies. Subjective manifestations were described in all cases, more frequently in a sensory rather than an emotional or psychological fashion. Focal seizures limited to subjective features were recorded in two patients. In one, psychological illusions and visual hallucinations were related to the superior frontal sulcus. Another presented isolated paraesthesia in the left arm with the implication of the supplementary motor area. Electrical stimulation of an electrode located in the premotor area evoked isolated subjective manifestations in three other patients. One patient reported sensory manifestations and another, ideational manifestations. Cephalic sensations and emotional manifestations were associated in one case. Subjective manifestations were observed in all patients, and were proved to be related to a discharge restricted to the premotor area in five. These were non-specific signs, but were always the same in a given patient. Spontaneous, isolated sensations and stimulation data tended to be contradictory. This illustrates the complexity of analyzing subjective signs, as well as the complexity of the neuronal networks participating in the propagation of discharges arising in the premotor frontal area.

Multicentric pleomorphic xanthoastrocytoma in a patient with neurofibromatosis type 1. Case report and review of the literature.

The authors report an unusual case of multicentric pleomorphic xanthoastrocytoma (PXA) in a 36-year-old woman with neurofibromatosis Type 1 (NF1). Both lesions were diagnosed as PXA but demonstrated different neuroimaging features and very different outcomes. Although the occipital lesion was cured surgically, the cerebellar tumor recurred three times and underwent malignant transformation into an anaplastic oligodendroglioma. The authors discuss the causes of PXA and suggest that it could originate from common bipotential precursor cells with two phenotypes.

Magnetoencephalographic studies of two cases of diffuse subcortical laminar heterotopia or so-called double cortex.

Two cases (a young male and a girl, suffering intractable epilepsy) of diffuse subcortical laminar heterotopia, or so-called double cortex (DC) have been investigated using magnetoencephalography (MEG). MEG confirmed involvement of both cortices (hetero- and normocortex) in the genesis of interictal spikes, and, according to the heterogeneity of DC syndrome, some differences were observed: spike initiation in the normocortex and latter involvement of the heterotopic cortex in the man, and rather a cancellation in both cortices in the girl. In addition, participation of heterotopic cortex in physiological activities could be demonstrated in the man.

Integration of sulcal and functional information for multimodal neuronavigation.

OBJECT: The authors present the use of cortical sulci, segmented from magnetic resonance (MR) imaging, and functional data from functional (f)MR imaging and magnetoencephalography (MEG) in the image-guided surgical management of lesions adjacent to the sensorimotor cortex. METHODS: In an initial set of 11 patients, sulci near lesions were automatically segmented from MR imaging data sets, then MEG and fMR imaging examinations were performed. Relevant functional information was preoperatively interpreted and selected from MEG and fMR imaging and subsequently transferred to the navigation system for selected sulci. A neuronavigation system consisting of a surgical microscope with enhanced reality overlay display was used. Data were displayed as contours on the cut-plane images of a stereotactic workstation and as contours on the overlay screen of the head-up display within the optical path of the right eyepiece of the surgical microscope. CONCLUSIONS: This method, in which both sulcal and functional mapping are used for surgery planning and neuronavigation, provides helpful information. It is a promising procedure for the treatment of patients who harbor lesions in areas around the eloquent cortex.