ABSTRACT
Seizures are due to excessively synchronous and/or excessively intense activity of neuronal circuits in the brain, particularly in the cerebral cortex. In epilepsy, seizures occur spontaneously, repeatedly, and usually suddenly. The unpredictability of seizures represents one of the main disabling features of epilepsy. This chapter will address mechanisms of focal (partial) epilepsy and seizures, i.e., cases where clinical evidence can identify some degree of localized seizure onset. The clinical consequences-the ictal semiology-will depend critically on where the focus is located and to some extent on the nature of the underlying molecular, structural, or functional pathology. The electrographic properties of seizures are a bit more consistent between cortical regions than are the associated semiologies, and, apart from distinguishing between hippocampus and neocortex, this review will not delve into regional differences.
