Definition of Partial (focal) seizure:

A partial seizure is an episode of abnormal electrical activity in one specific part of the brain.

Causes, incidence, and risk factors:

All seizures are caused by abnormal electrical disturbances in the brain. Partial (focal) seizures occur when this electrical activity remains confined to a limited area of the brain; they may sometimes progress to generalized seizures, which affect the whole brain.

Partial seizures can be further characterized as simple (not affecting awareness and memory) or complex (affecting awareness and memory of events before, during, and immediately after the seizure, and affecting behavior).

The abnormal electrical activity results from localized areas of abnormal brain tissue. These areas may have been present since birth or earlier (congenital), or they may develop following head trauma, infections, stroke, and certain other conditions. In many patients, no obvious cause can be determined. Partial seizures are more likely to be caused by a definable lesion in adults than in children.

A partial (focal) seizure may occur at any age, as a single episode or as a repeated, chronic seizure disorder (epilepsy). They are seen less frequently in children than in adults, but still account for about 45% of pediatric seizure disorders.

Risk factors include any injury to the brain. This includes trauma, stroke, brain tumors, infections (such as meningitis), or prior brain surgery.