Memory outcomes in mesial temporal lobe epilepsy surgery.

INTRODUCTION: Decline in verbal memory after dominant mesial temporal lobe surgery is a concern. Outcomes primarily reported by group data analysis do not address issues of practice effects and measurement errors and also do not provide information about individual meaningful change after surgery. Reliable Change Indices (RCI's) are regarded to be robust statistical methods for reporting individual change and have not been hitherto derived in patient populations in India.

AIM: Report memory outcomes for patients after surgery using group data as well as RCI score analyses using RCI scores derived in a control patient population.

METHOD: Retrospective data analysis of 106 selected patients who underwent Anterior Temporal Lobectomy (ATL) surgery. RCI scores derived from a control group of 44 non-operated patients. Outcomes based on score shifts on the various measures of two verbal and visual memory tests.

RESULTS: Group mean score analysis revealed no significant shifts in verbal or visual memory scores after left ATL, but significant improvements in verbal memory after right ATL. RCI score analysis revealed decline and improvements in a small percentage of patients for both left and right ATL groups. Percentage of patients showing decline was much less than reported in western literature although percentage improved was comparable.

DISCUSSION: Differences in decline percentage may be due to RCI scores and clinical characteristics of our sample (impaired pre-operative functioning, majority seizure free post surgery, moderate hippocampal sclerosis, early onset, long duration of seizures).

CONCLUSION: Group analyses mask individual change. Therefore, to report memory outcomes and counsel patients about relative risk-benefits of surgery, RCI scores derived from our patient populations should be used.