Abstracts

Rationale: Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. Quantitative morphometric magnetic resonance imaging (MRI) studies in patients with TLE have identified regional atrophy in temporal and extratemporal structures which are functionally and structurally connected. The clinical significance of this regional atrophy is unknown. The goal of this study is to identify patterns of regional cerebral atrophy in patients with TLE, and assess clinical significance.Methods: 34 patients with non-lesional TLE (NL-TLE) and 39 with mesial temporal sclerosis (MTS) were studied using 3 Tesla MRI. 37 patients had neuropsychology testing including intelligence, attention, processing speed, executive functions, language, visuoconstruction, verbal/visual memory, and motor speed tests. 22 age-matched controls were also scanned. Volumetric analysis was performed using Freesurfer software. Spearman's correlation coefficient was used to assess the relationship between atrophy and cognitive measures. False Discovery Rate (FDR) was used to correct for multiple comparisons.Results: Widespread atrophy of subcortical structures was demonstrated in hippocampus, thalamus, cerebellum, and brainstem. Neocortical atrophy was involved in both hemispheres in NL-TLE and MTS groups and the atrophy pattern was similar in both groups. In NL-TLE group (n=18), language was correlated with atrophy in anterior corpus collosum (r= 0.67). Immediate memory deficit was correlated with atrophy in left hippocampus, left pars opercularis, left superior parietal lobule, right pars orbitalis, and bilateral pars triangularis (r = 0.64 - 0.80). Impaired delayed memory was correlated with the atrophy of left hippocampus, left pars opercularis, right parsorbitalis, and right pars triangularis (r = 0.63 - 0.73). All correlations were statistically significant after FDR correction (FDR < 0.1). In LMTS (MTS with left temporal lobe seizure onset, n=8), immediate memory deficit was trendly correlated with the atrophy in left hippocampus and right putamen ( r= 0.81 0.88), Delayed memory performance was associated with the atrophy in left hippocampus, left amydala, left transverse temporal lobule ( r= 0.73- 0.83); In RMTS (MTS with right temporal lobe seizure onset, n=8), delayed memory deficit was correlated with the atrophy in left amydala ( r = 0.85), but no significant correlation between immediate memory measure and regional atrophy. All correlation had p < 0.01. Conclusions: Bilateral hippocampal and extra-temporal atrophy is common in TLE. Extra-temporal atrophy is associated with cognitive deficits, but the pattern is different in NL-TLE and MTS group. These findings provide insights into the brain networks involved in TLE with and without MTS.