Insights into the pathophysiology of psychomotor regression in CSWS syndromes from FDG-PET and EEG-fMRI

Epilepsy syndromes with continuous spikes-and-waves during slow sleep (CSWS) are age-related epileptic encephalopathies characterized by the development of various types of psychomotor regression in close temporal concordance with the appearance of the electroencephalography (EEG) pattern of CSWS. Functional cerebral imaging studies performed in children with CSWS have shown evidence for the existence of increase in metabolism or perfusion at the site of the epileptic focus, associated with decrease in metabolism or perfusion in distant and connected brain areas. Longitudinal [18F]-fluorodeoxyglucose–positron emission tomography (FDG-PET) studies and effective connectivity analyses have suggested the existence of a pathophysiologic link between increases and decreases in metabolism/perfusion that could be explained by the theory of remote inhibition. These findings highlight that the psychomotor regression observed in CSWS syndromes is not only related to the neurophysiologic impairment at the site of the epileptic foci but also to epilepsy-induced neurophysiologic changes in distant connected brain areas.