A systematic survey of the measures used to identify postoperative changes in language function following epilepsy surgery.

Epilepsy surgery, particularly dominant temporal lobe resection, poses a significant risk of post-surgical language decline. There is considerable heterogeneity in the language assessment protocols employed across epilepsy surgery centers. This in turn is reflected in the observed variability in the incidence of language decline reported in the literature. We systematically surveyed cognitive outcome literature to critically appraise the nature and frequency of language assessment in order to establish the parameters of the existing evidence base. We found that confrontation naming was the most frequently used paradigm to assess language function (96%), followed by verbal fluency (47%) and language comprehension (13%). Over 75% of studies reported outcomes within the first two years of surgery, and close to 50% used reliable change index (RCI) to measure pre-post change in function, which is considered to be the gold standard. The evidence base is currently saturated with short-term post-surgical language outcomes assessed at single-word level. Future studies employing comprehensive language assessment, longer follow-up intervals, and designs comparing different metrics of pre-post change in function are needed. PLAIN LANGUAGE SUMMARY: Patients undergoing surgery for temporal lobe epilepsy often experience a post-surgical decline in language functions. The degree and frequency of language decline reported in research literature are influenced by the protocols used to assess language functions. Upon reviewing language outcome studies, we note a predominance of naming outcomes at short follow-up intervals. Future studies incorporating comprehensive language testing at longer follow-up intervals are needed to better counsel epilepsy patients of their lifelong risks of language decline, and allow them to make an informed decision.