Volumetric changes in amygdala and entorhinal cortex and their relation to memory impairment in patients with medial temporal lobe epilepsy with visually normal MR imaging findings

•A study on MTLE with visually normal MR imaging findings.•To explore volumetric changes in amygdala and entorhinal cortex and their relation to memory impairment.•The volumetric asymmetry of the amygdala contributes to either verbal or nonverbal memory impairment in MTLE patients.

SummaryObjectiveTo explore the relation between parahippocampal structures, such as the amygdala and the entorhinal cortex (EC), with verbal and nonverbal memory in patients with medial temporal lobe epilepsy (MTLE) with visually normal MR imaging findings by volumetric measurements using magnetic resonance imaging (MRI).MethodsThirty-six consecutive patients with MTLE presenting a non-sclerotic hippocampus though visual inspection were assessed by MRI to measure the volumes of the hippocampus, amygdale and EC, and by using the clinical memory scale (CMS), a test battery for verbal and nonverbal memory, where summation of all CMS subscale scores equals the memory quotient (MQ). The correlations between MRI volumetric data (Z scores or asymmetry indexes (AI; (L − R)/(L + R)), “L” and “R” refer to the left and right volumes of each structure, respectively), clinical variables and memory scale scores were analyzed using a principal component regression model.ResultsVolumetric MRI revealed significant differences between the volumes of the hippocampus, EC, and right amygdala, but no differences in the volume of the left amygdala between the controls and the patients group. The patients group performed significantly worse in MQ (p < 0.01), the associate memory test (p < 0.01), directed memory test (p < 0.05), and the nonsense graphical recognition test (p < 0.05) compared to the control group. The asymmetry of the amygdala negatively correlated to verbal paired associates' recall and nonsense graphical recognition. The direct memory was positively related to the volume of the EC.ConclusionThe volumetric asymmetry of the amygdala contributes to either verbal or nonverbal memory impairment in MTLE patients. Verbal memory may correlate with the volume of the EC.