[Electrophysiology of transmissible encephalopathies]

The purpose of electrophysiological studies during the evolution of spongiform encephalopathies or prion diseases is to describe the changes of spontaneous or evoked electroencephalographic activity in natural and experimental diseases (natural and experimental scrapie, Kuru and Creutzfeldt-Jakob (CJ) disease in man and in different animal models) and to establish or to propose an action mechanism of the infectious agents. In the aim, the changes of electroencephalogram (EEG) and evoked potentials are described. Generally these modifications constitute an excellent and early marker of the initial phases of pathological mechanisms, replication of the agent and the cell membranes alterations. The changes of the sleep organisation occur generally later with the beginning of the clinical phase, just at the end of incubation period. The typical changes of EEG during the human CJ disease are rare in the experimental diseases. However, with animal models, it is possible to demonstrate the very univocal character of these diseases, creating pathophysiological modifications whose nature, origin and evolution are very comparable, with characteristic triade (loss of neurons, gliosis and spongiosis) and specific alterations of gabaergic, dopaminergic and inhibitory processes.