CORRELATION BETWEEN COMPUTED-TOMOGRAPHY AND VOLTAGE AND CURRENT SOURCE DENSITY SPECTRAL EEG PARAMETERS IN PATIENTS WITH BRAIN-LESIONS

In a group of patients with space-occupying brain lesions, CT measurem ents were correlated with absolute power (AP) and relative power (RP) of the delta, theta, alpha and beta EEG bands, calculated from the raw EEG potentials (EEGp) and from the Laplacian estimates also called '' current source densities'' (CSD). Rank correlations were calculated be tween the number of abnormal values in each band and the following CT measures: volume of the lesion and of the edema, density of the edema, percentage of ventricular collapse and midline shift. Abnormal spectr al values are those which are significantly higher than the norm for t he same age, in the delta and theta bands, and significantly lower in the alpha and beta bands. Spectral parameters obtained from the CSD sh owed higher correlations with CT measures than those calculated from t he EEGp. In the Laplacian, all CT measures had a significant correlati on with delta AP. Theta AP was significantly correlated with the volum e and density of the edema, as well as with midline shift. Significant correlations were also observed with delta and alpha RP. However, cha nges in RP were considered to be a consequence of the increase in delt a AP. Canonical correlation analyses between AP and RP calculated from EEGp or CSD and the first 3 CT measures showed that the volume of the lesion was only correlated with delta AP and RP. The volume and densi ty of the edema showed a significant correlation with delta, theta and alpha AP calculated from EEGp and only with theta and alpha AP in the Laplacian. Since the EEGp tends to produce a more extensive and diffu se picture of abnormality, whereas the Laplacian acts as a spatial fil ter emphasizing local sources over distant sources, we concluded that edema is related not to delta activity, but to the theta and alpha pow er.