Myoclonic seizures affect a small number of children and adults with generalized epilepsy of unknown cause (idiopathic). In children and teens with juvenile myoclonic epilepsy, the seizures seem to occur most often after waking up or while falling asleep.

During a myoclonic seizure:

• The arms, legs, torso, or facial muscles jerk rapidly as though they are being shocked.
• The body may jerk once or many times, on one or both sides of the body, in a rhythmic or random pattern.
• The person usually does not lose consciousness.

Myoclonic seizures are almost always very brief.