Tonic-clonic seizure: The classic type of epileptic seizure consisting of two phases to a tonic-clonic seizure -- the tonic phase and the clonic phase. In the tonic phase the body becomes entire rigid, and in the clonic phase there is uncontrolled jerking. Tonic-clonic seizures may or may not be preceded by an aura, and are often followed by headache, confusion, and sleep. They may last mere seconds, or continue for several minutes. Also known as a grand mal seizure.
If a tonic-clonic seizure does not resolve or if such seizures follow each other in rapid succession, seek emergency help. The person could be in a life-threatening state known as status epilepticus. See also: Status epilepticus.