Determination of language dominance using EEG spectral analysis versus the Wada test in temporal epilepsy (right-handed subjects)

Spectral analysis of the EEG alpha rhythm was studied in nine temporal epileptic right-handed patients in order to pi-edict localization of the speech area. We studied the variation of the spectral power of the alpha rhythm during nn activation paradigm previously validated ill normal right-handed subjects. Significant alpha power decreases in the left hemisphere during writing with the right hand ins compared to resting) and/or significant alpha power decreases in the right hemisphere during left-hand recognition and classification of cardboard objects las compared to resting) were considered as consistent with left-hemisphere dominance for language. The results of EEG spectral analysis were compared with those of the Wada test. The left hemisphere was dominant for language according to the Wada test in eight subjects and the right hemisphere in one subject. Six patients had a significant alpha power reduction in the hemisphere concerned during lateralized cognitive tasks, consistent with language localization in the left hemisphere according to the Wada test. The three remaining patients had no significant EEG spectral po,rer variations. A significant decrease of alpha power in the active hemisphere during cerebral activation seems statistically related to left-hemispheric dominance for language in right-handed subjects (hemispheric specialization). However; the localization of the speech area using this electrophysiological method does nor appear clinically relevant for a case-by-case decision in individual patients. (C) 1999 Editions scientifiques et medicales Elsevier SAS.