Cartographie d'amplitude dans les foyers de pointes EEG: étude des champs de potentiels

Abstract

Mapping study of EEG spike focus was performed on 122 topographic maps, from 88 records of 72 subjects, classified in: F for "functional" (no epileptic seizure); EGI, EGS and EGC: respectively generalized idiopathic, symptomatic and cryptogenic epilepsies; EPI, EPS and EPC: respectively partial idiopathic, symptomatic and cryptogenic epilepsies--epilepsies with centro-temporal spikes (EPR) are predominant in this group--; EI: indeterminate epilepsies. The graphoelements study: morphology, localization, amplitude, time course (sites of appearance, culmination and disappearance) and of electrical fields: distribution, monopolar, bipolar or intermediary aspect was performed. In order to quantify the brain mapping data we established series of numeric parameters: maximal negative and positive values; sum of the negative and positive values; ratio of these values. EGS and EPS groups have very variable map imaging for a patient or from a patient to another, r1 ratio is lower to 0.33. Idiopathic epilepsies are characterised by the stability of imaging, in the EGI group aspect is frequently monopolar with a central negativity, r1 and r2 ratios are high (0.9 and 1.2); in the EPI group the aspect can be monopolar or bipolar, in the EPR the aspect is stable, longitudinal bipolar, r1 and r2 ratios are between 0.33 and 0.99. In the EGC, EPC and EI groups there is no typical imaging, the mapping aspect can be monopolar or bipolar, in EGC and EPC r1 ratio is between 0 and 0.99, in EI r1 and r2 ratios are low (r1 = r2 = 0.2). In the F group the monopolar aspect is frequent. We can note the stability of the electrical fields apportionment in idiopathic epilepsies which is explainable by the integrity of the cerebral potential propagation pathways in spite of a dysfunction responsible of the epileptic seizures, the presence of a lesion is one of the responsible factors of the instability of the brain mapping.