Abnormalities of hippocampal signal intensity in patients with familial mesial temporal lobe epilepsy

RESUMO

Mesial temporal lobe epilepsy (MTLE) is associated with hippocampal atrophy and hippocampal signal abnormalities. In our series of familial MTLE (FMTLE), we found a high proportion of hippocampal abnormalities. To quantify signal abnormalities in patients with FMTLE we studied 152 individuals (46 of them asymptomatic) with FMTLE. We used NIH-Image© for volumetry and signal quantification in coronal T1 inversion recovery and T2 for all cross-sections of the hippocampus. Values diverging by 2 or more SD from the control mean were considered abnormal. T2 hippocampal signal abnormalities were found in 52 percent of all individuals: 54 percent of affected subjects and 48 percent of asymptomatic subjects. T1 hippocampal signal changes were found in 34 percent of all individuals: 42.5 percent of affected subjects and 15 percent of asymptomatic subjects. Analysis of the hippocampal head (first three slices) revealed T2 abnormalities in 73 percent of all individuals (74 percent of affected subjects and 72 percent of asymptomatic subjects) and T1 abnormalities in 59 percent (67 percent of affected subjects and 41 percent of asymptomatic subjects). Affected individuals had smaller volumes than controls (P < 0.0001). There was no difference in hippocampal volumes between asymptomatic subjects and controls, although 39 percent of asymptomatic patients had hippocampal atrophy. Patients with an abnormal hippocampal signal (133 individuals) had smaller ipsilateral volume, but no linear correlation could be determined. Hippocampal signal abnormalities in FMTLE were more frequently found in the hippocampal head in both affected and asymptomatic family members, including those with normal volumes. These results indicate that subtle abnormalities leading to an abnormal hippocampal signal in FMTLE are not necessarily related to seizures and may be determined by genetic factors.