EEG markers of the stabilotraining effect during the rehabilitation of patients with posttraumatic Korsakoff’s syndrome

Nine patients with posttraumatic Korsakoff syndrome (KS) were examined before and after a rehabilitation course of feedback stability training (ST) using EEG, posturographic and clinical tests (with the FIM and Mayo Portland scales used for estimation). During 7 to 12 sessions, the patients tried to perform static and motor tasks. A group of 18 healthy subjects were examined to provide standard parameters. The results demonstrated a disturbed spatiotemporal EEG pattern in patients with KS before ST in the form of a reduced coherence for short derivation pairs (intrahemispheric, interhemispheric, and diagonal ones) in frontal and parietooccipital areas. Analysis of specific EEG rhythms demonstrated the maximum decrease in coherence in the α band (with the aforementioned regional specificity) and for long diagonal pairs (between the left frontal and right parietooccipital areas). The ST course was accompanied by KS regression (according to clinical scales and posturographic study); an original increase in EEG coherence, especially that of α waves, was recorded in the occipitoparietal and central frontal areas of the right hemisphere; a subsequent increase in coherence of the frontal areas in both hemispheres was observed. Late after the ST course, further positive changes were characteristic of the EEG spatiotemporal pattern. However, comparison with standard data suggested incomplete recovery of various coherence parameters: hypertrophied coherence in intrahemispheric pairs and still reduced values in interhemispheric derivations. This EEG pattern suggested incomplete KS regression, which was confirmed by clinical data.