The impact of epilepsy surgery on cognition and behavior.

Famous historical cases and current clinical experience clearly indicate that the success of epilepsy surgery cannot be judged with the basic algorithm "fewer seizures = better outcome." Many factors combine and entwine with the experience of medically intractable seizures to create associated patterns of behavior and cognition. Obtaining freedom from seizures does not automatically undo the historical tangle of these salient factors, many of which remain or are exacerbated after surgery. This review examines the preoperative, perioperative, and postoperative factors that influence postoperative cognition and behavior in adult patients with temporal lobe epilepsy. Consistent findings from group studies have long masked the considerable individual variations in cognitive and behavioral outcomes following surgery. Although more recent multivariate studies provide useful clinical data for prospective surgical candidates, comprehensive long-term follow-up studies are rare. We have certainly become more proficient at measuring both cognitive and behavioral outcomes following surgery, although the ecological validity of many follow-up measures, particularly in the cognitive domain, remains low. A reliance on test scores can mask significant differences in strategy, which can also be used as a sign of lateralized dysfunction. A shift away from the "can do versus can't do" approach to the assessment of cognitive strategies may hold the key to more meaningful pre- and postoperative cognitive assessments from the patient's perspective. Emergent functional imaging paradigms show much promise in this regard. A renewed focus on cognitive strategies may also be useful in planning postoperative rehabilitation programs. New directions for outcome research in epilepsy surgery are suggested with an emphasis on a patient-centered approach.