Epilepsy, grand mal: Epilepsy that includes tonic-clonic (grand mal) seizures, which are the most obvious type of seizure. There are two parts to a tonic-clonic seizure. In the tonic phase, the body becomes rigid, and in the clonic phase, there is uncontrolled jerking. A tonic-clonic seizure may or may not be preceded by an aura, and these seizures are often followed by headache, confusion, and sleep. They may last for mere seconds or continue for several minutes. If a tonic-clonic seizure does not resolve or if such seizures follow each other in rapid succession, emergency help is needed because the patient could be in a life-threatening state known as status epilepticus. Treatment is with antiseizure medications.