A partial complex seizure is a brief and temporary alteration in brain function. It is caused by abnormal electrical activity in a specific, discrete area of the brain. The seizure is characterized by a change in alertness or awareness, behavioral or emotional symptoms, and temporary loss of memory. See also temporal lobe seizure.

Partial complex seizures may occur at any age, as a single episode or as a repeated, chronic condition (seizure disorder, epilepsy). They are uncommon in very young children.

During the normal functioning of the brain, information is transmitted from nerve cell to nerve cell by an electrochemical process. This process can be detected as electrical activity by an electroencephalograph (EEG). Abnormal patterns of electrical activity are associated with seizures.

Given sufficient circumstances, any person will have a seizure. Partial complex seizures are usually the result of abnormal electrical activity in the temporal lobes of the brain. The most common cause is when a specific area of the brain has been damaged by lack of oxygen, trauma, brain tumors, or discrete brain lesions of any sort.

In tissue studies, about 47% of children with partial complex seizures were found to have hippocampal sclerosis (hardening in the area of the brain called the hippocampus).