[Rhythms of falling asleep persisting in adults. Two cases without mental deficiency]

Nocturnal rhythmic movements (jactatio capitis nocturnus, JCN) are very frequent in young children but persist only rarely in adults; studies including sleep recordings are exceptional in those cases. We report two new cases of young adults with JCN persisting since the first year of life, associated with restless sleep and diurnal sleepiness. Several episodes of JCN were recorded in each of the two patients; they always occurred after a period of paradoxical sleep, the waking phase preceding the rhythmic movements which are sometimes very short (1 s). The pathophysiology of adult JCN is discussed as a behavioral disorder of sleep onset conditioning or a disorder of sleep maintenance.