Clinical Neuroscience

[SPECTRAL EEG-CHARACTERISTICS OF SUBCORTICAL ISCHEMIC BRAIN LESION - A CASE STUDY]

MOLNÁR Márk, CSUHAJ Roland, HORVÁTH Szabolcs, VASTAGH Ildikó, GAÁL Zsófia Anna, CZIGLER Balázs, BÁLINT Andrea, NAGY Zoltán

MARCH 30, 2006

Clinical Neuroscience - 2006;59(03-04)

[Introduction - Although the EEG-changes caused by ischemic stroke are well known, data of the literature are rather ambiguous. The EEGfindings recorded in a patient with a unilateral subcortical ischemic lesion are evaluated with special emphasis related to the effect of the dynamics caused by eyes opening. Participants and methods - Data recorded from a patient (54 years old male with a completed stroke involving the frontal and parietal subcortical region in the left side) were compared to those of a control group (12 healthy age matched subjects). Absolute and relative frequency spectra, theta/beta quotients, the interaction index characterizing the effect of eyes opening and the symmetry index were calculated from the EEG recorded in eyes closed and eyes open conditions. Data of the patient were compared to those recorded in the control group on the basis of 95% confidance intervals. Results - Irrespective of the recording conditions the predominance of slow activity and the increase of theta/beta quotients were found in the absolute frequency spectra. The increase of beta1 and beta2 frequency bands following eyes opening on the side of the lesion were found to be less obvious than that seen on the intact side and that observed in the control group. With respect to the interaction index related to the side differences caused by eyes opening the change of the beta2 frequency band was found to be the most conspicuous. The symmetry index underscored the predominance of slow (delta, theta, alpha1) frequencies on the lesion side, and that of the fast (beta1, beta2) frequencies on the intact side in both recording conditions. Conclusions - Localized lesion of the white matter without cortical damage can cause the predominance of slow activity and decrease of the fast frequency bands on the side of the lesion which can be shown by the absolute frequency spectra and is revealed by the symmetry index. The lack of functional reactivity of the fast frequencies in the side of the lesion can clearly be seen in the change of relative spectra following eyes opening and on the basis of the calculation of the interaction index reflecting the dynamics of side differences.]

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