Abstracts

The majority of patients with PNES fail relatively easy tests of recognition memory (the Word Memory Test, or WMT) at twice the rate of patients with documented epilepsy, suggesting a greater prevalence of poor effort that invalidates neuropsychological test results (Williamson et al., 2003). Unfortunately, exploration of the effects of this [ldquo]poor effort[rdquo] on other neuropsychological tests has been limited. This project addresses this by assessing the effect of WMT failure across a range of neurocognitive measures. We hypothesized that:
(a) Patients who fail the WMT will perform significantly worse on a range of neurocognitive tests than patients who pass the WMT.
(b) If the lack of discriminability between epilepsy patients and PNES patients on neurocognitive testing is driven by effort rather than by common neuropathological substrates that affect cognition, then PNES patients who put forth valid effort should outperform epilepsy patients who put forth valid effort 97 patients who have comprehensive diagnostic workups including video telemetry were diagnosed as having exclusively epileptic seizures (n=68) or exclusively psychogenic nonepileptic seizures (n=29). Level of cognitive performance was indexed by the Dodrill Discrimination Index (DDI), which depicts the percentage of 16 tests on which patients performed below normal limits. Diagnostic groups were compared overall and as stratified by WMT performance. The DDI of epilepsy patients did not differ from that of PNES patients (p = .213). However, the groups varied significantly when viewed in light of WMT performance (p [lt] .001). The PNES patients who put forth valid effort significantly outperformed all other groups, including the patients with epilepsy who put forth valid effort (p [lt] .01). The groups that put forth valid effort outperformed the groups that did not. Finally, the epilepsy and PNES patients that failed the WMT did not differ from each other (p = .904). 1. Patients who fail the WMT perform much more poorly than those patients who pass the WMT across a range of neurocognitive measures. Some epilepsy patients who perform in this range have had seizures within the 48 hours preceding the testing, and others have documented, lifelong evidence of significant cognitive impairment. In contrast, there is no known brain-behavior relationship that could account for this level of performance in patients with PNES, most of whom live independently.
2. The common wisdom is wrong. Level of performance in neurocognitive testing differentiate patients with epilepsy from patients with PNES - if one compares PNES patients who are putting forth valid effort.