1. A method, comprising: sensing a time of beat sequence of a patient's heart; processing the time of beat sequence with a medical device to identify a change in heart rate of a patient from a first heart rate to a second heart rate; determining with the medical device a ratio of the second heart rate to the first heart rate; continuously updating the first heart rate; autonomously determining with the medical device a first dynamic ratio threshold for the ratio based on a first patient activity and a second dynamic ratio threshold for the ratio based on a second patient activity; autonomously determining with the medical device a current dynamic ratio threshold for the ratio which is within a range between the first dynamic ratio threshold and the second dynamic ratio threshold, wherein the current dynamic ratio threshold is based upon a most recently updated window of the first heart rate; comparing the ratio to the current dynamic ratio threshold; and detecting a neurologic event based on an occurrence of the ratio exceeding the current dynamic ratio threshold.