Methods and devices for detecting and/or predicting onset of an undesirable physiological event or neural state, such as an epileptic seizure, facilitate rapid intervention with a treatment therapy such as neurostimulation or drug therapy. The methods and devices involve monitoring the patient's body temperature, preferably by an implanted temperature sensor, to detect a change in a body temperature parameter over a first time period, which may comprise an increase or decrease in the patient's body temperature, time rate of change of body temperature, moving average temperature, increase or decrease in body temperature exceeding a target temperature, elevated or reduced body temperature, or temperature stability parameter over a first time period. The sampling period may be changed manually or depending upon a sensed body parameter, including temperature. When a parameter change is detected that exceeds a threshold, neurostimulation therapy is delivered to a neural structure of the patient.