Hippocampal sclerosis is characterized pathologically by loss of pyramidal neurons, granule cell dispersion and gliosis in the hippocampus. It can be associated with changes in nearby structures, known as mesial temporal sclerosis. It a common cause of temporal lobe seizures that do not respond to medication. It is an acquired structural abnormality, and is known to occur as a consequence of seizures, especially prolonged febrile seizures. It can co-occur with other structural brain abnormalities, including malformations of cortical development and vascular malformations (e.g. Sturge-Weber syndrome), known as 'dual pathology'.
The clinical presentation of hippocampal sclerosis is with seizures with mesial temporal features, and there may be cognitive deficits that relate to the hippocampus affected (verbal memory impairment in dominant hippocampal sclerosis, visual memory impairment in non dominant hippocampal sclerosis). Presentation may relate to the associated structural or genetic co-occurring condition, if present. For example, around 25% of patients with hippocampal sclerosis may have a history of febrile seizures, especially prolonged febrile seizures. In these individuals, the self-limited syndrome of febrile seizures is followed by a latent period, and then seizures with mesial temporal features appear.