Electroclinical markers to differentiate between focal and generalized epilepsies

Generalized-onset seizures originate at a point within the brain and rapidly engage bilaterally distributed networks, whilst focal-onset seizures originate within networks limited to one hemisphere which may be discretely localized or more widely distributed. Challenges in data capturing have resulted in a lack of consistency across incidence and prevalence studies for estimates of generalized versus focal epilepsies in population groups, with a preponderance of unclassified cases. Infants and young children can further challenge delineation due to variable expression at different stages of brain maturation and impaired ability to express sensory seizure semiology. Focal seizures are divided into those in which the affected person is aware and those with impaired awareness; these events can be motor or non-motor. Generalized seizures are also categorized as motor and non-motor, but loss of awareness occurs with most events. Delineation between generalized and focal epilepsies is important for ongoing management. EEG, neuroimaging and other investigations (genetics, immune markers, etc.) can support the outcome but distinction between focal and generalized epilepsy in isolation is rarely achieved using such techniques. Certain clinical settings such as age, underlying aetiologies, and co-morbidities may be more predisposed to specific types of epilepsy. The differentiation between generalized and focal seizures remains a clinical process based on meticulous clinical history and examination, and is of relevance for the selection of antiseizure medications and identification of patients who may be viable for epilepsy surgery.