Abstracts

RATIONALE: The association between febrile seizures, drug-resistant medial temporal lobe epilepsy (MTLE) and hippocampal sclerosis (HS) is well established. More recently, subtle malformations of the hippocampus have been described in patients with MTLE. Nevertheless, the clinical profile of patients with MTLE associated with hippocampal malformations (HM) is still discussed. The aim of our study was to compare the clinical profile of patients with MTLE associated with HM to that of patients with HS.
METHODS: Twenty-nine adult patients (age 41[plusminus]12 yrs, mean[plusminus]SD; 15 women/14 men) with MTLE and hippocampal abnormalities detected by MRI were included. MRI included coronal T1- and T2-weighted images, perpendicular to the long axis of the hippocampus. Images were independently reviewed by 2 neurologists and one neuroradiologist, blinded to the clinical data. Criteria for HM were : (1) a medial position of the hippocampus close to the midline, leaving empty the choroid fissure (2) an hippocampus that was abnormally round or pyramidal in shape and vertically oriented (3) a parahippocampal gyrus with an horizontal portion reduced and a collateral sulcus deeper than normal. Patients were divided into 3 groups : patients with isolated HM; patients with isolated HS and patients with HM associated with a small hippocampus. Clinical features, including familial history of epilepsy, history early events (in particular febrile seizures), age at onset, latent period, seizure types and severity of epilepsy assessed by the percentage of seizure-free patients were analyzed.
RESULTS: Five patients had isolated HM, 18 patients had isolated HS and 6 patients had HM associated with a small hippocampus. Familial history of epilepsy, mean age at seizure onset, duration of the latent period and seizure types were not statistically different in the 3 groups. By contrast, the prevalence of early events was significantly different in the 3 groups (72% in patients with HS, 33% in patients with HM associated with HS, 0% in patients with isolated HM; p[lt]0.05). The number of seizure-free patients was also statistically different (5% in patients with HS, 17% in patients with HM associated with a small hippocampus, 60% in patients with isolated HM; p=0.02).
CONCLUSIONS: Our study suggests that patients with isolated hippocampal malformations have less frequent prior history of early events and less severe epilepsy than patients with HS. These results suggest that the pathophysiology of MTLE associated with HM differs from that of MTLE associated with HS. Further studies are needed to investigate if patients with HM are as good candidates for surgery as patients with HS.