Abstracts

Rationale: The hippocampus plays a crucial role in learning and memory. Episodic memory has been associated with the mesial temporal lobe (MTL, Squire & Zola-Morgan, 1991). Hippocampal sclerosis (HS) is the most common pathological finding in MTL epilepsy (MTLE), and neuronal cell loss has been related with memory impairment (Baxendale et al. 1998, Rausch & Babb 1993, Coras et al. 2014). The aim of the study was to relate hippocampal subfields neuronal cell densities and pre-operative neuropsychological scores regarding visual and verbal episodic memories and language tests.Methods: We evaluated 58 right-handed patients with MTLE and HS submitted to surgery. The hippocampi were collected and prepared for histopathological examination. HS pattern was determined and neuronal cell density was measured. Two language tests (Verbal Fluency and Naming), two verbal (RAVLT and Logical Memory) and two nonverbal memory tests (Visual Reproduction – VR and Complex Rey Figure – CRF), immediate and delayed recall, were applied. Statistic method: ANOVA (p=0.05) and Spearman's test.Results: Patients were divided into two groups, left (n=28) and right HS (n=30). There were no statistical differences between groups regarding IQ and/or educational level. There were differences in CRF (immediate p=0.01; delayed recall p=0.03), patients with right HS had a worse performance. Left HS group showed no correlation between neuropsychological tests and hippocampal subfields. Right HS group showed positive correlation between CRF, both immediate (p=0.007) and recall (p=0.013), with CA2 neuronal density; immediate VR also positively correlated with CA3 (p=0.036) and delayed VR with CA4 cell density (p=0.025).Conclusions: Despite the fact that literature describes only correlation between verbal memory tests and hippocampal subfields in left HS groups (Baxendale et al. 1998, Rausch & Babb 1993, Coras et al. 2014), in agreement with other results from our group (Neves et al. 2012), there was correlation between right hippocampal subfields neuronal densities in CA2, CA3 and CA4 and visual memory tests, both immediate and delayed recall. This work was funded by FAPESP, CAPES, and CNPq. References: Squire LR, Zola-Morgan S. The medial temporal lobe memory system. Science 1991;253(5026):1380-6. Baxendale SA, Van Paesschen W, Thompson PJ, et al. Hippocampal cell loss and gliosis: relationship to preoperative and postoperative memory function. Neuropsychiatry Neuropsychol Behav Neurol 1998;11(1):12-21. Rausch R, Babb TL. Hippocampal neuron loss and memory scores before and after temporal lobe surgery for epilepsy. Arch Neurol 1993;50(8):812-7. Coras R, Pauli E, Li J, et al. Differential influence of hippocampal subfields to memory formation: insights from patients with temporal lobe epilepsy. Brain 2014;137(Pt 7):1945-57. Neves RS, de Souza Silva Tudesco I, Jardim AP, et al. Granule cell dispersion is associated with memory impairment in right mesial temporal lobe epilepsy. Seizure 2012;21(9):685-90.