Accelerated long-term forgetting after amygdalohippocampectomy in temporal lobe epilepsy

•ALF does not result from a single pathological process.•The improvement of post-op consolidation is evidence for a correlation between epileptic activity and ALF.•There is a direct correlation between left hippocampal/temporal tissue loss and initial low memory performance in L-TLE irrespective of epileptic activity.•There is ALF in the TLE group during the early stage.•There is no ALF in the R-TLE group.•A separate assessment of early and late performance in TLE patients appears to be important. Temporal lobe epilepsy (TLE) has been associated with the phenomenon of accelerated long-term forgetting (ALF). In this study, we aimed to demonstrate the effect of surgery on the ALF phenomena thus contributing to potential explanation of the causal mechanism. We evaluated 51 patients with TLE related to hippocampal sclerosis who had amygdalohippocampectomy and had remained seizure-free after surgery. A control group consisted of 24 healthy individuals. All were given a verbal learning test assessing recall after 30 min, 1 week and 6 weeks. In our study, the Left-TLE (L-TLE) group showed a statistically significant reduction in the performance at all assessment intervals from 30 min to 1 week compared to the Right-TLE and control groups regarding verbal learning memory test (VLMT) as well as for logical memory. The forgetting rates in the VLMT from 30 min to 1 week were not statistically significantly different between all 3 groups. The logical memory test results equally showed no statistically significant difference in the forgetting rates for the 3 groups between 30 min and 1 week. These results may support ongoing debates assuming the initial low performance in the memory of L-TLE patients to be directly related with left hippocampal-temporal tissue loss irrespective of epileptic activity. The discovery of the ALF phenomenon explains that standard memory tests are unable to detect memory loss in some patients who are experiencing a significant level of problems with forgetfulness in their daily lives.