Hippocampus Sparing Resections within the Temporal Lobe in Adolescents with Epilepsy: Impact on Cognition and Remaining Hippocampal Volume

Background/Purpose: Resections within the language dominant temporal lobe including hippocampectomy bear the risk of postoperative verbal memory decline. Thus, there has been a tendency toward tailored resections, sparing the hippocampus if clinically indicated.

Methods: Retrospectively, the impact of epilepsy surgery within the language dominant left temporal lobe on memory performance (learning, delayed free recall, recognition) as well as on postoperative hippocampal volume were investigated in a subgroup of 20 adolescent patients with left-sided temporal lobe epilepsy (age 16–22 years, MW ± SD = 18 ± 3 years, age at epilepsy onset 14 ± 5 years). Memory performance of 10 patients with hippocampus sparing resections (HC-S) were compared with that of 10 patients with hippocampus resections (HC-R) matched for IQ, age, and age at epilepsy onset (non-parametric comparisons). Postoperative memory change was correlated with alterations in hippocampal volume (VBM-analysis) after surgery (Spearman).

Results: Both groups showed similar preoperative memory performance (p > 0.3) and revealed no significant postoperative difference neither between nor within groups. Examination of individual cases indicated significant decline (more than 1 SD) in the HC-R group more frequently: Learning HC-S 10%, HC-R 40%; Delayed free recall HC-S 30%, HC-R 50%; Recognition HC-S 10%, HC-R 20%. After hippocampus sparing resection a significant ipsilateral hippocampal volume loss was observed (2.3 ± 0.4 cm³ preop. 1.6 ± 0.5 cm³ postop., p < 0.05). Left hippocampal volume reduction was associated with postoperative decline of verbal free recall (r = 0.8, p < 0.05).

Conclusion: After hippocampal sparing resections ipsilateral hippocampal volume loss as well as an association between volume loss and verbal memory decrease can be observed.