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

Abstract

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% of all individuals: 54% of affected subjects and 48% of asymptomatic subjects. T1 hippocampal signal changes were found in 34% of all individuals: 42.5% of affected subjects and 15% of asymptomatic subjects. Analysis of the hippocampal head (first three slices) revealed T2 abnormalities in 73% of all individuals (74% of affected subjects and 72% of asymptomatic subjects) and T1 abnormalities in 59% (67% of affected subjects and 41% 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% 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.

Gene expression profile suggests different mechanisms underlying sporadic and familial mesial temporal lobe epilepsy

“…38 Nonetheless, structural abnormalities outside the mesial portion of the temporal lobe were similar in both forms of MTLE. 44 These findings, combined with previous results, 32,33 suggest that genetic factors may predispose some individuals to develop hippocampal abnormalities that may be further intensified by recurrent seizures; 30 however, to date, no studies addressing the molecular mechanisms possibly involved in familial MTLE have been performed, including gene expression analysis.…”

“…35,46 Family history of epilepsy was considered positive when the patient had at least two first-or second-degree relatives with MTLE, as defined by diagnostic criteria proposed previously and accepted by the literature in the field of epilepsy and by the International League Against epilepsy. 2,3,7,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]45 None of the patients included in the present study had any generalized or complex partial seizures documented 48 h before or during epilepsy surgery. This project was approved by the Research Ethics Committee of the University of Campinas (ethics approval # CAAE: 12112913.3.0000.5404), and all patients signed a consent form to donate part of the surgical tissue to research.…”

A Locus Identified on Chromosome18P11.31 is Associated with Hippocampal Abnormalities in a Family with Mesial Temporal Lobe Epilepsy

“…In the present study we used MRI signs of HAb to classify individuals as affected, independently of the presence of seizures (individual I-2, F-10; Kobayashi et al, 2002, 2003; Coan et al, 2004). …”

“…HA with or without hyperintense T2 signal on MRI was observed in most patients, including those with a single focal seizure, seizure remission (Kobayashi et al, 2003) as well as in 34% of asymptomatic first-degree relatives of patients with familial MTLE (Kobayashi et al, 2002). These reports suggest that hippocampal abnormalities (HAb) identified by MRI in familial MTLE have a genetic predisposition and it is not necessarily associated to seizures in all patients (Kobayashi et al, 2001; Coan et al, 2004). …”

Narrative review of epilepsy: getting the most out of your neuroimaging

“…Although the dentate gyrus, the CA1, CA4 and to a lesser degree CA3 sections of the hippocampus are primarily involved, regional involvement may be difficult to characterize on clinical MRI exams and does not impact the clinical management of the patients. On MRI, coronal T2-w and FLAIR images are the most sensitive for detecting abnormal signal, while T1 3D can better define the loss of hippocampal gyration (34). Some authors (35) have reported that MR qualitative imaging have a sensitivity ranging from 80% to 90% in the evaluation of mesiotemporal sclerosis while using quantitative assessment the sensitivity rises to 90% to 95%.…”