gms | German Medical Science

Objective: Hippocampal sclerosis (HS) is the most frequent histopathological finding after hippocampal resection in patients suffering from drug-resistant mesial temporal lobe epilepsy (MTLE). However, in a number of cases the histopathological specimen reveals astrogliosis (AG) instead of HS. There is a controversial discussion about the role of astrogliosis on disease pathophysiology and its impact on the clinical course. The aim of this study was to investigate whether the course of epilepsy and postsurgical seizure outcome are different in patients displaying HS as compared to those with AG.

Methods: The authors retrospectively reviewed 635 patients (females n=325, 51%), who underwent either a standard anterior temporal lobe resection (ATL) or selective amygdalahippocampectomy (SAH) for drug-resistant MTLE between 09/1989 and 04/2012. Only patients with HS or AG were included in the study and distributed into two different groups according to the histopathological findings. Comprehensive data concerning the course of epilepsy and seizure outcome were evaluated. Seizure outcome was evaluated according to the ILAE classification.

Results: HS was diagnosed in 562 (88%) patients whereas 73 (12%) samples showed AG. The mean follow-up period was 56 months after surgery. At last available follow up 67% of the patients in the HS group were seizure free (ILAE 1) compared to 45% of the patients in the AG group (p=0.0002, RR=1.7, CI=1.2-2.2). The onset of epilepsy was earlier in the HS group than in the AG group (12.3 vs. 16.1 years, p=0.0037). A subgroup (20 AG and 40 HS) of pre-operative MRI images was analyzed for hippocampal signal intensity (SI), showing high SI value in all cases. Visual analysis revealed either hyperintense (AG 85%; HS 10%) or markedly hyperintense (AG 15%; HS 90%) (p<0.001) lesions, although the objective SI measurement showed no difference between groups. Duration of epilepsy was no prognosticator for the overall seizure outcome (p=0.3) either for AG or HS. The multivariate regression analysis confirmed astrogliosis (p=0.0031) as independent predictor for worse seizure outcome, while duration of epilepsy, type of surgery and side of surgery did not influence the final seizure outcome.

Conclusion: The histopathological finding of hippocampal astrogliosis in MTLE shows an important impact on the clinical course of epilepsy. Although patients with AG develop epilepsy later in life, they have a significantly worse chance to become seizure free after epilepsy surgery. These results suggest that astrogliosis and hippocampus sclerosis represent two different diseases entities, a fact that should be critically taken into consideration when counselling patients with drug-resistant MTLE.