Age of seizure onset as a major determinant of memory changes following surgery for hippocampal sclerosis

ObjectiveTo study the relation of epileptological and surgical variables with post-operative memory performance, following surgery for refractory mesial temporal lobe epilepsy (MTLE) due to hippocampal sclerosis (HS).\n\nMethodsLogical memory (LM) and visual memory (VM) scores for immediate and late recall of 201 patients operated for MTLE/HS from 1996 to 2016 were reviewed. All patients were evaluated prior to surgery and reevaluated up until 5 years after the procedure. Scores were standardized to a control group of 54 healthy individuals matched for age and education. Patients were divided in two groups according to the hemisphere affected and scores for immediate and late recall were compared. Reliable Change Index (RCI) with a 90% confidence interval was performed to verify individual memory changes for each late LM (lLM) and late VM (lVM) score. A multiple linear regression was performed with the RCI using late recall scores of lLM and lVM and clinical variables.\n\nResults112 (56%) patients had left HS (lHS). The lHS group showed decreased immediate LM (iLM) scores before and after surgery (p<0.05), compared with rHS. The rHS group showed increased iLM scores post-operatively (p<0.05). RCI of the rHS group showed that 6 (7%) individuals had improved, 78 (87%) stabilized and 5 (6%) decresead in lLM scores, and for lVM 7 (8%) improved, 80 (89%) stabilized and 2 (3%) worsened (RCI> 1.645). RCI of the lHS group showed that 3 (3%) individuals had increased scores, 104 (93%) stabilized and 5 (4%) worsened for lLM, and for lVM 3 (3%) obtained improved scores, 103 (92%) stabilized and 6 (5%) decreased (RCI> 1.645). lHS and later age of onset of the first epileptic seizure were predictors of lLM loss (p<0.05).\n\nConclusionLeft MTLE/HS and later age of seizure onset were predictive factors for worsening of lLM. No RCI predictors of post-op lVM performance were identified. We found a decreased baseline functioning of LM in the lHS group and improvement of LM in some patients who had resection of the right MTL. Patients of the rHS group had a higher percentage of reliable post-op improvement for both VM and LM scores.