Hippocampal sclerosis

Hippocampal sclerosis (HS) represents the most common neuropathological finding in patients undergoing surgery for intractable temporal lobe epilepsy (TLE). Recent neuropathological and clinical observations indicate that HS is not always a uniform entity. In addition to classic HS, described by Sommer in 1880, there is increasing evidence of atypical HS patterns and widespread pathology involving the limbic structures in TLE patients. These variations could influence surgical outcome, as suggested by recent studies. A longstanding question, since the earliest descriptions of this pathology, is whether HS represents the cause or the consequence of chronic seizure activity. The expansion of neurosurgical epilepsy programs has offered the possibility of disposing of clinically well-characterized hippocampal tissue used to study the structural and functional reorganization occurring in the hippocampus and their contribution to the process of epileptogenesis. However, neuropathological postmortem studies have also contributed to the understanding of the pathological cascade that leads to TLE with HS. A major challenge for both neuropathologists and clinicians is to understand why some patients with HS fail to become, or remain, seizure free after epilepsy surgery. This will require the detection of appropriate patient populations, based on a better definition of distinct clinicopathological subtypes of TLE patients with HS.