Determining reliable cognitive change after epilepsy surgery: development of reliable change indices and standardized regression-based change norms for the WMS-III and WAIS-III.
OBJECTIVE
Reliable change indices (RCIs) and standardized regression-based (SRB) change scores norms were established for the recently revised Wechsler Adult Intelligence Scale-III (WAIS-III) and Wechsler Memory Scale-III (WMS-III) in patients with complex partial seizures. Establishment of such standardized change scores can be useful in determining the effects of epilepsy surgery on cognitive functioning independent of test-retest artifacts including practice effects.


METHODS
Forty-two nonoperated-on adult patients with complex partial seizures (primarily of temporal lobe onset) were administered the WMS-III and WAIS-III on two occasions (mean 7-month interval). All patients were receiving stable antiepileptic drug (AED) treatment at both testings. RCI and SRB change scores were calculated. Confidence interval cutoff scores (90% and 80%) and standardized regression equations were calculated for each of the WAIS-III and WMS-III Primary Indices and individual subtests. Age, gender, education, test-retest interval, preoperative test performance, seizure onset, and seizure duration were predictor variables for the SRB equations.


RESULTS
Test-retest reliabilities for the WAIS-III and WMS-III Primary Indices were within acceptable ranges, although considerable individual subtest variability was found. Preoperative performance was the single largest contributor to each of the predictive regression equations. Age, gender, education, seizure onset, and seizure duration contributed modest variance to several of the regression equations.


CONCLUSIONS
We calculated both RCI and SRB change score indices for the recently revised Wechsler instruments. These formulas help control for test-retest methodologic artifacts and provide a standardized method with which to examine both individual and group level cognitive change after epilepsy surgery.
Martin
Roy
R
Department of Neurology and UAB Epilepsy Center, University of Alabama at Birmingham, Birmingham, Alabama 35294-0021, USA. martin@uab.edu
Sawrie
Stephen
S
Gilliam
Frank
F
Mackey
Melissa
M
Faught
Edward
E
Knowlton
Robert
R
Kuzniekcy
Ruben
R
D000328:Adult; D001925:Brain Damage, Chronic / Q000175:diagnosis*; D003072:Cognition Disorders / Q000175:diagnosis*; D017029:Epilepsy, Complex Partial / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis*; D011594:Psychometrics; D012016:Reference Values; D015203:Reproducibility of Results; D014888:Wechsler Scales / Q000706:statistics & numerical data*