Experimental kuru in the rhesus monkey: a study of EEG modifications in the waking state and during sleep.

EEG patterns recorded in the waking state and during sleep were studied in 6 rhesus monkeys inoculated with a strain of Kuru previously passaged in rhesus monkey (ENAGE strain, rhesus L6 56). The onset of the disease was confirmed by the appearance of various clinical signs in 4 monkeys 15 months after inoculation. At the 16th month, the first EEG modifications appeared during sleep, which became lighter. The waking EEG was abnormal during the mature phase of the disease; it was characterized by slow anomalies and scattered spikes. The sleep EEG still presented 3 stages of Slow Wave Sleep which, however, were totally unlike the physiological stages. REM sleep rapidly disappeared, as did the cyclic organization pattern. Irritative phenomena became very significant and, in particular, very frequent 'tonic seizures' were observed. Experimental Kuru thus appears, in the rhesus monkey, as an epileptogenic encephalopathy, which is differentiated from both the human disease and the experimental disease in the chimpanzee.