Abstracts

Rationale: Mesial temporal sclerosis (MTS) is the most common pathological abnormality associated with temporal lobe epilepsy (TLE). Several Magnetic Resonance Image (MRI) investigations of patients with TLE/MTS demonstrated a diverse range of structural abnormalities extending beyond the ipsilateral hippocampus. Voxel-based morphometry (VBM) may identify gray and white matter abnormalities. The aim of this study was to investigate brain morphology and its relation with natural history and clinical features in patients with refractory TLE/MTS using VBM. Methods: One hundred patients with unilateral TLE/MTS (59 left, 41 right) underwent a comprehensive pre-surgical evaluation including a 1.5T MRI and prolonged video-EEG monitoring. All patients had clear MRI findings and epileptogenic zone consistent with unilateral MTS. Thirty normal controls formed the comparison group. Predefined aspects were analyzed: initial precipitating injury (IPI) mainly simple or complex febrile seizures (FS) and status epilepticus (SE), age at onset of habitual seizures, duration of epilepsy and types of auras. Results: Compared to controls TLE patients had reduced gray matter volume (GMV) in bilateral frontal and parietal cortices, thalamus and cerebellum. Significant ipsilateral GMV reductions in hippocampus, neocortical temporal regions and insula were observed when left TLE and right TLE groups were compared. Left TLE patients presented more widespread reductions extending to left uncus, precentral gyrus, thalamus, inferior parietal lobule, cuneus, fusiform gyrus and bilateral posterior cingulum. For both, FS and SE, reductions were observed in several regions outside temporal lobe, as occipital cortex, insula, cingulum and putamen. Patients with left TLE showed more widespread damage, through temporal and extratemporal regions. In right TLE group reductions were more evident in medial temporal lobe structures. Auras were classified in medial, lateral and multiple or extratemporal. In medial auras, significant ipsilateral reductions in hippocampus and amygdala were observed. Evident reductions were observed in bilateral hippocampus, amygdala and insula in patients with lateral auras, which were more widespread in left TLE. The group with multiple or extratemporal auras presented the greatest reductions. In left TLE group, GMV reductions were apparent in left hippocampus, bilateral parietal and occipital lobes, ipsilateral temporal gyri, amygdala, insula and caudate. Conclusions: In TLE/MTS structural abnormalities extend beyond hippocampus and extratemporal damage is more pronounced in left hemisphere. Different types of IPI and auras seem to be implicated on the degree of extratemporal involvement.