EMPIRICAL TECHNIQUES FOR DETERMINING THE RELIABILITY, MAGNITUDE, AND PATTERN OF NEUROPSYCHOLOGICAL CHANGE AFTER EPILEPSY SURGERY

Purpose: We assessed test-retest neuropsychological performance in pat ients with complex partial seizures to derive reliable change indices (RCIs) and regression-based norms for change, indices that may be help ful in assessing cognitive outcome after anterior temporal lobectomy. Methods: Forty patients with complex partial seizures (CPS) who did no t undergo epilepsy surgery were administered a comprehensive neuropsyc hological battery on two occasions. Their test-retest data were used t o compute both RCIs and regression-based norms for change for each neu ropsychological index, RCIs corrected for practice effects provide a c onfidence interval (CI) indicating the degree of performance change re quired to exceed the variability attributable to sources of error (e.g ., practice, test-retest reliability). Regression-based norms for chan ge also correct for several sources of measurement error and examine o bserved versus expected test-retest changes on a common metric, thereb y facilitating determination of the degree and relative magnitude of c hange across cognitive domains. Results: Mean changes in test-retest p erformance were generally modest, but were evident across several test measures. Our data indicate a considerable degree of individual varia bility in test-retest performance. Conclusions: RCIs and regression-ba sed norms are complementary indexes and can be particularly useful in examining the test-retest performance of individual patients who under go epilepsy surgery as well as in the more general investigation of co gnitive outcome after epilepsy surgery.