A system for detecting an epileptic seizure in a prone person, comprising:at least one motion sensor with at least one measurement axis having fastening means for securing said motion sensor to said personfirst means for determining a first probability of at least a first state transition diagram of the nocturnal activity of a prone person with respect to data representing the measurement signals of the motion sensor, said first diagram comprising predetermined probabilities of oriented transitions between two different or identical states, the probabilities of the states of said first diagram being predetermined andsecond means for determining a second probability of at least a second state transition diagram for an epileptic seizure with respect to data representing the measurement signals of the motion sensor, said second diagram comprising predetermined probabilities of oriented transitions between two different or identical states, the probabilities of the states of said second diagram being predetermined.
