Mammillary Body Atrophy in Temporal Lobe Epilepsy With Hippocampal Sclerosis

Abstract

Background and purpose: We aimed to determine 1) the frequency of mammillary body (MB) atrophy in patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS), 2) the clinical significance of MB atrophy, and 3) the association between MB atrophy and volume changes in other subcortical limbic structures.

Methods: We enrolled 69 patients with pathologically confirmed TLE with HS, who underwent a standard anterior temporal lobectomy, as well as 40 healthy controls. We used the FreeSurfer deep-learning tool of U-Net to obtain the volumes of the subcortical limbic structures, including the MB, hypothalamus, basal forebrain, septal nuclei, fornix, and nucleus accumbens. MB atrophy was considered to be present when the MB volume was decreased relative to the healthy controls.

Results: MB atrophy was present in 18 (26.1%) of the 69 patients with TLE and HS. Among the clinical characteristics, the mean age at seizure onset was higher (25.5 vs. 15.9 years, p=0.027) and the median duration of epilepsy was shorter (149 vs. 295 months, p=0.003) in patients with than without MB atrophy. The basal forebrain (0.0185% vs. 0.0221%, p=0.004) and septal nuclei (0.0062% vs. 0.0075%, p=0.003) in the ipsilateral hemisphere of HS were smaller in the patients with MB atrophy.

Conclusions: We observed ipsilateral MB atrophy in about one-quarter of patients with TLE and HS. The severity of subcortical limbic structure abnormalities was greater in patients without MB atrophy. These findings suggest that MB atrophy in TLE with HS is not rare, but it has little clinical significance.

Keywords: epilepsy; magnetic resonance imaging; mammillary body.

Fig. 1. Example of segmentation of subcortical limbic structures, including the mammillary body (MB). The segmentations are overlaid onto T1-weighted images in coronal, axial, and sagittal orientations, with a volume rendering also shown. AntCom, anterior commissure; HypoThal-noMB, hypothalamus; SeptalNuc, septal nucleus. Adapted from Kang et al. J Neurol 2022 Jul 9 (https://doi.org/10.1007/s00415-022-11263-z), with permission from Springer Nature.