Hypnic Jerk

A hypnic jerk, hypnagogic jerk, sleep start, or night start, is an involuntary myoclonic twitch which occurs during hypnagogia, just as the subject is beginning to fall asleep, often causing him or her to awaken suddenly. Physically, hypnic jerks resemble the “jump” experienced by a person when startled,^[1]often accompanied by a falling sensation.^[2] A higher occurrence in people with irregular sleep schedules is reported.^[3]