Evaluation of MRI and auditory function in patients undergoing surgery for mesial temporal sclerosis and temporal lobe epilepsy

Objective: The aim of this study is to quantitatively investigate volumetric changes in auditory network structures using magnetic resonance imaging (MRI) in patients who underwent resective surgery for mesial temporal sclerosis (MTS), by comparing preoperative and postoperative findings, and to discuss their implications in terms of hearing and central auditory processing. Materials and Methods: This retrospective longitudinal study included adult patients diagnosed with mesial temporal sclerosis (MTS) who underwent anterior temporal lobectomy and amygdalohippocampectomy, and who had high-quality 3T brain MRI scans available from both preoperative and postoperative periods. MRI data were processed using the CAT12 toolbox running on SPM25, and volumetric measurements of 35 cortical and subcortical regions related to the surgical area and the auditory network were obtained for each patient. Preoperative and postoperative regional brain volumes of the same patients were compared. For the analysis of dependent measurements, the non-parametric Wilcoxon Signed-Rank test was used. Results: In the preoperative and postoperative volumetric comparison of the 15 included patients, a significant volume reduction was observed only in the CA2-3 subregion and the alveus within the contralateral hippocampal subfields analysis. Additionally, postoperative volume increases were detected in the contralateral planum polare and centromedian nucleus. On the ipsilateral side, increased volumes were observed in the angular gyrus and supramarginal gyrus, whereas significant reductions were found in the transvers temporal gyrus, medial geniculate nucleus, anterior and posterior insula (including total insular volume), lingual gyrus, mammillary body, planum temporale, and thalamus. Notably, both ipsilateral and contralateral reductions were identified in the fornix and striatum volumes. Conclusion: In our study, ipsilateral volume reductions were observed in the primary auditory structures -namely, the transvers temporal gyrus and medial geniculate nucleus- following mesial temporal lobe epilepsy (MTLE) surgery, while volume increases were found in the angular gyrus and supramarginal gyrus, regions involved in auditory-cognitive integration. This pattern suggests a neuroplastic response in higher-level semantic and phonological processing areas, compensating for reductions in basic auditory components. Volume changes in contralateral hippocampal CA2-3, alveus, planum polare, and centromedian nucleus indicate possible postoperative effects on the opposite hemisphere. Bilateral volume losses in connecting structures such as the fornix and striatum support the presence of widespread network involvement. These findings imply that MTLE surgery impacts not only the targeted mesial regions but also broader auditory and limbic networks. Therefore, incorporating advanced auditory processing assessments alongside pure tone audiometry is of clinical importance for a comprehensive functional evaluation.