BOLDly Going Where Few Researchers Have Gone Before—Leveraging Language-Related Hippocampal Activations to Predict Postoperative Memory Decline

Hippocampal Activations Obtained During Language fMRI Tasks: A Complementary Tool for Predicting Postoperative Memory Prognosis Salleles E, Samson S, Denos M, Mere M, Lehericy S, Herlin B, Dupont S. Epilepsy Res . 2024;205:107405. doi: 10.1016/j.eplepsyres . 2024.107405. PMID: 39002388. In medial temporal lobe epilepsy (MTLE), the benefits of surgery must be balanced against the risk of postoperative memory decline. Prediction of postoperative outcomes based on functional magnetic resonance imaging (fMRI) tasks is increasingly common but remains uncertain. The aim of this retrospective study was to determine whether hippocampal activations elicited by fMRI language tasks could enhance or refine memory fMRI in MTLE patient candidates to surgery. Forty-six patients were included: 30 right and 16 left MTLE, mostly with hippocampal sclerosis. Preoperative assessment included neuropsychological tests and fMRI with language (syntactic verbal fluency) and memory tasks (encoding, delayed, and immediate recognition of images of objects). Thirty patients underwent surgery and had neuropsychological evaluations 1 year after surgery. Worsening was defined as a degradation of more than 10% in postoperative forgetting scores compared to preoperative scores in verbal, nonverbal and global memory. Memory fMRI had the best sensitivity with hippocampal activations obtained in 95% of patients, versus 65% with language fMRI. Considering the patients who elicited a hippocampal activation, language fMRI led to 80%, 65% and 85% of correct predictions for respectively global, verbal and nonverbal memory (vs 71%, 64%, and 68% with memory fMRI). Memory and language fMRI predictions outperformed those made by neuropsychological tests. In summary, language fMRI was less sensitive than memory fMRI to elicit hippocampal activations but when it did, the proportion of correct memory predictions was better. Moreover, it proved to be an independent predictive factor regardless of the side of the epileptic focus. Given the ease of setting up a language task in fMRI, we recommend the systematic combination of memory and language tasks to predict the postoperative memory outcome of MTLE patients undergoing epilepsy surgery.