Relevance of hippocampal integrity for memory outcome after surgical treatment of mesial temporal lobe epilepsy

Abstract

Surgical treatment of unilateral mesial temporal lobe epilepsy (mTLE) particularly bears the risk of episodic memory decline. The present study investigates the role of the ipsilateral hippocampal integrity for postoperative change in material-specific memory performance. In 104 patients who had undergone epilepsy surgery for unilateral mTLE, we analyzed pre- to postoperative changes of verbal and figural memory as a function of segmental neuronal cell densities of the resected hippocampus (cornu ammonis, CA1-4; internal and external limb of the dentate gyrus, DG). Results were controlled for side of surgery and hemispheric dominance. Surgery caused significant memory decline, especially with regard to verbal memory after left temporal resections. Seizure freedom (65 % Engel Ia) did not affect memory outcome. Higher neuronal cell densities of the resected left hippocampus were associated with greater declines in verbal memory parameters (r = -0.27 to r = -0.39, p < 0.05), especially when excluding patients with atypical hemispheric dominance (r = -0.34 to r = -0.60, p < 0.05; significant correlations across all hippocampal subfields). There were no systematic correlations between neuronal cell densities of the resected right hippocampus and memory changes. The results emphasize the role of the structural and functional integrity of the hippocampus within the left dominant hemisphere for the degree of verbal memory decline after temporal lobe surgery. Presurgical verbal memory performance may be taken as a marker of ipsilateral left hippocampal integrity and may contribute to individual risk-benefit evaluations before epilepsy surgery. Finally, more precise neuropsychological markers of right hippocampal integrity are needed.

Characterising subtypes of hippocampal sclerosis and reorganization: correlation with pre and postoperative memory deficit

“…Further decline in memory following temporal lobe surgery is reported to occur in up to 25%, with older patients being particularly vulnerable . A better‐preserved hippocampus has been shown to be predictive of greater postoperative decline in verbal memory function and more significant postoperative memory declines have been reported with ILAE type 2 HS or better preserved CA1 . In terms of quantitative confirmation of regional neuronal preservation in the present study, we identified a statistical association between MAP2 labeling only in the subiculum and naming decline at 1 year.…”

Histopathologic subtype of hippocampal sclerosis and episodic memory performance before and after temporal lobectomy for epilepsy

“…Initial research has suggested that TLE patients with type 2 pathology have intact preoperative memory ability that is comparable to that of patients with nonlesional TLE and significantly better than performance of individuals with types 1 or 3 . Furthermore, some data suggest that type 2 pathology is overrepresented among patients with left TLE and intact word list learning scores; however, cases of type 2 with episodic memory deficiencies have also been documented . Further, there is evidence to suggest that overall degree of neuronal loss may be a more important factor in episodic memory performance than the pattern of cell loss or the hippocampal subregions within which neuronal loss occurs .…”

“…1 HS has long been associated with episodic memory impairments in patients with TLE as well as better prognosis for memory outcome following temporal lobectomy. 4,5 Although many studies over the years have examined the relationship between hippocampal cell loss/ density and memory ability, [6][7][8][9][10][11][12] little is known about episodic memory ability/outcomes as they pertain to the HS pathology subtypes outlined in the ILAE Consensus guidelines. 1 Initial research has suggested that TLE patients with type 2 pathology have intact preoperative memory ability that is comparable to that of patients with nonlesional TLE and significantly better than performance of individuals with types 1 or 3.…”

“…13 Furthermore, some data suggest that type 2 pathology is overrepresented among patients with left TLE and intact word list learning scores 14 ; however, cases of type 2 with episodic memory deficiencies have also been documented. 11,15 Further, there is evidence to suggest that overall degree of neuronal loss may be a more important factor in episodic memory performance than the pattern of cell loss or the hippocampal subregions within which neuronal loss occurs. 10,15 The limited data available regarding HS ILAE subtype and memory outcome following epilepsy surgery have been conflicting.…”

Evaluación de la memoria en la epilepsia del lóbulo temporal para predecir sus cambios tras la cirugía. Una revisión sistemática

“…Sin embargo, la intervención implica un riesgo de deterioro de la memoria, con efectos diferenciales en la memoria verbal y no verbal, en pacientes con ELTm izquierda o derecha respectivamente, siendo la memoria verbal la más vulnerable [3][4][5][6][7] . Por ello, previo a la cirugía, es necesario realizar una completa evaluación del paciente, que incluye una historia clínica detallada, y al menos, EEG, pruebas de neuroimagen (resonancia magnética [RM]) y una correcta evaluación cognitiva.…”