Determining meaningful neuropsychological changes following epilepsy surgery for Chinese-speaking patients in Taiwan

This study aimed to develop reliable change index (RCI) and standardized regression-based (SRB) change scores for Chinese versions of the neuropsychological tests to provide an empirical standard for evaluating meaningful cognitive changes after epilepsy surgery for patients with temporal lobe epilepsy (TLE).

Thirty-one non-operated patients with TLE were assessed twice (6-month interval) by using the Wechsler Adult Intelligence Scale-III (WAIS-III) and the subtests of the Wechsler Memory Scale-III (WMS-III) to compute RCI with the correction of practice effect and SRB equations. The predictor variables for the SRB models included the demographic variables (age, gender, education), clinical variables (age of seizure onset, seizure duration), and baseline performance. These standards were then applied to sixty patients who underwent selective amygdalohippocampectomy (SAH).

Test-retest reliability was acceptable while the individual subtest variability was noted (r = 0.51 to 0.94). Baseline performance was the primary predictor in each SRB equation, accounting for 31.4% to 88.4% of the variance. Among the SAH cohort, 80.0%-100.0% remained cognitively stable across different tests. However, the patients in left SAH group exhibited a significant decline in verbal memory (20.0-23.3%), working memory and executive control (6.7-30.0%). Conversely, more than 10% of the right SAH group showed deterioration in visual memory and processing speed.

This study developed and demonstrated the clinical applicability of disease-specific, population-specific RCI and SRB indices for Traditional Chinese-speaking patients with TLE. These indices provide a standardized framework for accounting for practice effects, regression to the mean, and test-retest variability when interpreting meaningful cognitive changes following epilepsy surgery.