The classification of seizures is based on clinical and EEG manifestations and is mainly divided into focal seizures (partial seizures, of which there are significant differences in clinical manifestations and severity between the different types) and generalised seizures (tonic, clonic, tonic-clonic, myoclonic, disorientation, etc.). Focal seizures are seizures that begin with clinical symptoms and EEG changes suggesting the earliest activation of some neurons confined to one hemisphere. Partial seizures are further classified based on the presence or absence of impairment of consciousness during the seizure and the ability to progress to a generalized seizure. Symptoms during a full-blown seizure up to the onset of the seizure suggest bilateral hemispheric involvement, impaired consciousness appears and may be the initial manifestation, and motor symptoms are bilateral. The EEG pattern during seizure onset is bilateral neuronal firing.