During a clonic seizure, a person may lose control of bodily functions and begin jerking in various parts of the body. He/She may temporarily lose consciousness, followed by confusion.

Clonic seizures begin in early childhood. They often appear to be a case of massive bilateral epileptic myoclonus, though the motor features of it may be less symmetrical. With time, clonic seizures may eventually progress to generalized tonic-clonic seizures.