Predicting Verbal Memory Outcomes after Anterior Temporal Lobectomy

There is considerable concern regarding verbal memory decline (estimated rate of 44% measured by test scores), after dominant temporal lobe surgery (Sherman et al, 2011). It is important to delineate factors that predict postsurgical memory decline as epilepsy surgery is an elective procedure, and patients need to understand relative risks and benefits of the procedure.

Aim: To study the factors predicting postoperative verbal memory outcome.

Method Retrospective data analysis of 233 adult patients who underwent anterior temporal lobectomy (115 left, 118 right) and had a 1-year postsurgical follow-up evaluation. Multiple regression analysis was performed with the dependent variable being postsurgery verbal memory test score, and multiple independent variables being demographic, seizures, surgery side, mood issues, subjective memory complaints, intelligence quotient (IQ), and preoperative verbal memory test scores. Reliable Change Index scores were used to identify patients who experienced a significant decline in verbal memory functioning.

Results: Eleven percent (n = 26) patients demonstrated a significant postoperative decline in verbal memory as per RCI score calculations. Fifty-six percent (R2 = 0.56, p < 0.001) of the variance in the data was explained by the predictor variables; with side of resection (p < 0.001), preoperative memory scores (p < 0.001), and preoperative IQ (p < 0.01) as the most significant factors.

Conclusion: Preoperative verbal memory score, IQ, and the side of surgery appear to be risk factors for developing a verbal memory decline postsurgery. Evaluating patients on standardized neuropsychological tests pre-surgery is critical to identify patients at risk and to guide the preoperative counseling and plan the postoperative memory rehabilitation.