Hippocampal sclerosis is the most common structural brain abnormality that is treated with epilepsy surgery in adults. Seizures with mesial temporal lobe features occur, with epigastric or experiential aura followed by loss of awareness. Anterior temporal spikes or sharp waves may be seen on interictal EEG. Neuroimaging shows unilateral hippocampal atrophy with T2-hyperintense signal.
This etiology is associated with seizures that have onset from the first decade of life to early adulthood. Both sexes are affected. Birth history is usually normal. Typically seizures start after a latent period following an antecedent event e.g. febrile seizures (seen in 25%, especially if prolonged) or head trauma. However in more than half of cases, there is no known antecedent. Neurological examination and head size are normal. Patients typically have neuropsychological deficits that depend on the side of hippocampal sclerosis.