Abstracts

Recent investigations have demonstrated that the majority of patients with psychogenic nonepileptic seizures (PNES) perform in the invalid range on tests designed to detect valid effort on neurocognitive testing (Williamson et al., 2003, 2004). However, a small percentage of patients with video-telemetry confirmed epilepsy also fail symptom validity testing (SVT), including some without evidence of somatoform disorder or apparent motivation to perform in a suboptimal manner. There are inconsistent findings about the extent to which recent epileptiform activity influences neurocognitive performance (Aldenkamp [amp] Arends, 2004). Clinically, we noted that patients with epilepsy who experienced seizures within the past 24 hours seemed more likely to fail symptom validity testing. We investigated this matter in a more systematic fashion to determine the extent to which recent seizure activity may compromise the validity of neurocognitive findings. Sixty-three patients referred for continuous video-EEG monitoring for evaluation of uncontrolled seizures at the University of Washington were administered the Word Memory Test as part of a comprehensive epilepsy neuropsychological evaluation. Only patients classified on the basis of their ictal EEG recordings and behavioral presentation as experiencing epileptic seizures were included in the study. In order to screen out patients with known cognitive deficits severe enough to decrease the likelihood of normal performance on SVT, patients unable to live independently were excluded. Of the patients who failed SVT, 75% had suffered a seizure within the preceding 24-hour period. ROC analysis suggests that simply knowing that a patient had suffered a seizure within the preceding 24 hours significantly improves one[apos]s ability to predict whether they will fail SVT (p = .03). These findings appear to be particularly true for patients diagnosed with complex partial seizures: 3/8 patients with complex-partial seizures with a right-sided focus who had suffered a recent seizure failed (vs. 0/8 who had not seized), whereas 5/8 patients with a recent left-sided focal seizure failed (vs. 0/8 who had not seized). Based upon these preliminary data, it appears that suffering a seizure within 24 hours of neurocognitive testing may place a sizeable proportion of patients with epilepsy at risk for failing SVT, particularly if a patient suffers from complex partial seizures. Given the demonstrated relationship between failed SVT and improbably poor scores on neurocognitive testing in epilepsy and other populations, this may have important implications for clinical decision-making based upon such test results.