The Full form of GTCS is Generalized Tonic-Clonic Seizure. GTCS, commonly known as a grand mal seizure, is a type of generalized seizure that produces bilateral, convulsive tonic and clonic muscle contractions. Tonic-clonic seizures are the seizure type most commonly associated with epilepsy and seizures in general and the most common seizure associated with metabolic imbalances. It is a misconception that they are the sole type of seizure, however, as they are the main seizure type in only 10% of those with epilepsy. These seizures typically initiate abruptly with either a generalized or focal onset. A vague sense of impending seizure (prodrome) may also be present before the seizure begins. The seizure itself includes both clonic and tonic contractions, with tonic contractions usually preceding clonic contractions. After these series of contractions, there is an extended postictal state where the person is commonly sleeping with loud snoring and is unresponsive. There is usually pronounced confusion upon awakening. The vast majority of generalized seizures are idiopathic. Some generalized seizures start as a smaller seizure that occurs solely on one side of the brain, however, and is referred to as a focal (or partial) seizure.