Background Gliosis only (GO) and hippocampal sclerosis (HS) are distinct histopathological entities in mesial temporal lobe epilepsy. This study explores whether this distinction also exists on a functional level when evaluating pre- and postoperative memory.
Methods Using a retrospective matched case–control study design, we analysed verbal and visual memory performance in 49 patients with GO and 49 patients with HS before and one year after elective surgery.
Results Clinical differences were evident with a later age at seizure onset (18±12 vs 12±9 years) and fewer postoperative seizure-free patients in the GO group (63% vs 82%). Preoperatively, group and individual-level data demonstrated that memory impairments were less frequent, less severe and relatively non-specific in patients with GO compared with HS. Postoperatively, verbal memory declined in both groups, particularly after left-sided resections, with more significant losses in patients with GO. Factoring in floor effects, GO was also associated with more significant visual memory loss, particularly after left resections.
Conclusions Compared with HS, GO is characterised by (1) a later onset of epilepsy, (2) less pronounced and more non-specific memory impairments before surgery, (3) a less successful surgical outcome and (4) a more significant memory decline after surgery. Overall, our results regarding cognition provide further evidence that GO and HS are distinct clinical entities. Functional integrity of the hippocampus appears higher in GO, as indicated by a better preoperative memory performance and worse memory outcome after surgery. The different risk–benefit ratios should be considered during presurgical patient counselling.
- EPILEPSY, SURGERY
- LIMBIC SYSTEM
Data availability statement
No data are available.
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Contributors JT, J-AW, CH, AG and DD generated the hypotheses and study design. All authors provided data and discussed the analysis plan. Results were discussed by all authors. All authors provided input to the manuscript. All authors were responsible for the critical revision of the article. All authors had access to the final study results and were responsible for the final approval of the manuscript. The corresponding author attested that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. JT accepts full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests CEE has served as a paid consultant for Desitin, Pfizer and UCB Pharma, outside of the submitted work; CH reports personal fees from Precisis, Eisai, UCB and GW, outside the submitted work; J-AW reports personal fees from Eisai, outside the submitted work; JT reports grants from EpiCARE & Arbeitsgemeinschaft für Prächirurgische Epilepsiediagnostik und operative Epilepsietherapie AG, outside the submitted work; DD, AG, AJB, EH and JE declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Provenance and peer review Not commissioned; externally peer reviewed.