According to http://www.doctortipster.com here are some things to know about seizures.
Generalized Tonic-Clonic Epilepsy Seizures (Grand Mal Seizures) – Clinical Presentation
Epilepsy is a chronic cerebral disorder characterized by recurrent and spontaneous seizures that are typically unprovoked and unpredicteble.
An epilepsy seizure represents a transient episode of supratentorial origin, characterized by an abrupt and temporary alteration of cerebral function, due to an abnormal paroxysmal discharge of cerebral neurons caused by cortical hyperexcitability. According to The International Classification of Seizures, epilepsy seizures are divided into partial seizures ( focal or localization-related seizures) and generalized seizures.
Partial seizures are subdivided into simple partial seizures in which there is no loss of consciousness and into complex partial seizures which are always associated with loss of consciousness. Partial seizures are the result of an abnormal paroxysmal discharge of cerebral neurons within a particular brain region and they manifest focal symptoms an may progress to generalized seizures.
Generalized seizures are the result of an paroxysmal discharge that probably begins in thalamus and then spreads to other brain structures, but on electroencephalographic (EEG) recordings, they appear to start simultaneously in both cerebral hemispheres. Generalized seizures are always associated with loss of consciousness and generalized symptoms.
Generalized Tonic-Clonic Epilepsy Seizures (Grand Mal Seizures)
Grand mal seizures or primary generalized seizures represent the most frequent form of epilepsy seizures and typically include four phases, out of which the first two phases may be absent, but the third phase is always present. This four phases are represented by prodromal phase, aura, tonico-clonic phase and postictal phase.
Below is a video that shows all 4 stages of a Grand Mal Seizure.