Abstracts

Rationale: Accurate differential diagnosis of ES vs. NES has important implications for treatment. Traditionally, the gold standard for epilepsy diagnosis is the VEEG and ictal semiology. Because NES is presumed to have a psychogenic component, assessment of psychological factors is also an important contributor to the diagnostic process. The Personality Assessment Inventory (PAI) is an inventory designed to evaluate emotional and psychological status. The PAI includes scales to measure health concerns and symptoms of somatization and conversion disorders. Wagner et al. (2005) proposed an NES indicator derived from the PAI Somatization subscales as a noninvasive screening tool to aid in differential diagnosis of ES/NES. Methods: A retrospective chart review of 172 consecutive admissions to the Yale Epilepsy Surgery Program monitoring unit was conducted. The sample consisted of 58 males and 105 females and the majority of patients (77%) were Caucasian. Nine patients were excluded (4 dual ES/NES diagnosis; 5 for invalid PAI). Based on 24-hour VEEG, an epileptologist classified these cases into two groups; 132 patients were diagnosed with ES and 31 with NES. Mean age of the sample was 38.2 years (SD = 12.6). Patients completing the PAI were also administered tests for intelligence (WAIS-III or WASI). The NES indicator score was calculated by subtracting the Health Concerns T-score from the Conversion T-score where positive scores yielded a classification of NES.Results: When relying on the NES indicator alone, close to one-third of each group was misclassified. Specifically, a descriptive analysis suggested 32% of the NES diagnosed patients were classified as ES and 26% of ES diagnosed patients were classified as NES. The NES group scores were significantly higher (meaning more abnormal) in several of the PAI domains including Somatization (M=76.94; SD=15.00) and Conversion (M=79.00; SD=19.16) subscales. The two groups also differed significantly on FSIQ scores. The ES group performed in the average range and NES in the low average range (Table 1). Conclusions: Using a larger NES sample in our cross-validation study, the results indicated a significant difference in PAI scales between ES and NES groups; however, the NES indicator alone allowed for one-third of misclassification among both groups. There were also several additional significant PAI findings for NES (Table 1), but no clear pattern to distinguish NES from ES. Further, our NES population had lower FSIQ scores, which could be an indication that there are fundamental differences between our NES group and Wagner’s et al. (2005) NES groups. We did not replicate Wagner’s et al. findings that the NES indicator is a reliable instrument to distinguish NES from ES; however, the NES indicator is a good basis for future research to consider. Further studies are needed that includes larger NES populations (including both inpatients and outpatient) and cross validation among patients in other epilepsy programs. This could refine the NES indicator and validate it as an effective diagnostic adjunct for NES.