Longer-term verbal and visual memory patterns in patients with temporal lobe and genetic generalized epilepsies

To compare forgetting patterns between patients with temporal lobe (TLE) and generalized (GGE) epilepsies and to assess whether recall is associated with epileptic activity.

Thirty-three patients with TLE (13 left, 17 right, and 3 nonlateralized TLE), 42 patients with GGE, and 57 healthy controls (HCs) were asked to recall words, verbal story material, and the Rey-Osterrieth complex figure at two delays. Accelerated long-term forgetting (ALF) was defined by group performance comparable to HCs at 30 min and worse recall than HCs after 4 weeks. ALF was assessed by comparing raw test scores in a two-way repeated measures analysis of variance (ANOVA) adjusted for the learning capacity.

Compared to HCs, patients with R-TLE remembered fewer items of the word list after 30 min as well as after 4 weeks. Patients with L-TLE and GGE had comparable learning-adjusted performance to HCs at the 30 min delay but scored less after 4 weeks (group by delay interaction F(3, 124) = 3.2, P = 0.026, ${\eta }_p^2$  = 0.07). The epilepsy group (patients with TLE and GGE combined) performed as well as HCs at 30 min but worse after 4 weeks irrespective of experienced seizures during the 4-week delay or interictal bilateral (TLE) or generalized (GGE) activity before the study. We noted no statistically significant differences between patient and HC verbal story (group by delay interaction F(3, 124) = 0.7, P = 0.570, ${\eta }_p^2$  = 0.02) or complex figure (F(3, 124) = 0.8, P = 0.488, ${\eta }_p^2$  = 0.02) recall.

Our data support verbal and visual memory impairment in both TLE and GGE with different performances between these groups in the task of word recall. We suggest the presence of ALF in patients with GGE and left TLE after adjusting for learning capacity. We could not confirm the influence of epileptic activity on long-term forgetting patterns. Future studies are required to better define domain-specific differences in memory impairment in TLE and GGE.