Abstracts

Rationale: Identification of clinically relevant subgroups among patients with psychogenic non-epileptic seizures (PNES) or epileptic seizures (ES) may be useful in assessing prognosis, and evaluating the effectiveness of emerging therapies. Effort or motivation on cognitive testing, as measured by performance validity tests (PVTs), may be one such classification criterion. In other patient populations poor performance on PVTs has been associated with unreliable test results and increased health care utilization, suggesting a distinct subgroup. Methods: The COVE (Characteristics of Veterans with Epilepsy) study prospectively evaluated consecutive Veterans entering the EMUs of the Portland Oregon, San Francisco California, and Madison Wisconsin VA Epilepsy Centers of Excellence. Patients underwent continuous video-EEG monitoring. EMU seizure diagnoses followed standardized criteria. Research evaluations included 2 PVTs: (1) Test of Memory Malingering (TOMM), a widely used standalone PVT in the format of an easy visual recognition memory test; and (2) Repeatable Battery for Assessment of Neuropsychological Symptoms –Effort Index (RBANS-EI), an embedded validity measure within the RBANS cognitive battery. Psychiatric diagnoses were obtained using the Structured Clinical Interview for DSM IV. Severity of current PTSD and depression symptoms were measured using the PTSD checklist (PCL) and the Beck Depression Inventory (BDI-II). Quality of life was measured using the Quality of Life in Epilepsy inventory (QOLIE-31). Results: 81 patients met research criteria for the diagnosis of PNES, and 70 met criteria for ES. 17.3% of patients diagnosed with PNES had a TOMM score <=45 (on either trial 2 or the retention trial; threshold for invalid responding) vs. 10.8% of patients with ES (ns). 17.8% of patients with PNES has an RBANS-EI >=3 (invalid threshold) vs. 12.5% of patients with ES (ns). 9.7% of patients with PNES had invalid responding on both measures (vs. 4.8% of ES patients; ns). Invalid responding on the TOMM and on the RBANS-EI were correlated (r=0.47; p<0.001). Patients with invalid (vs. valid) TOMM scores had lower scores on 5 of 6 RBANS cognitive domains including the Total Scale (p<0.001). These patients also had lower (worse) QOLIE-31 scores, and higher (worse) scores on the PCL and BDI-II (all p<0.05). Differences between the PNES and ES groups were not significant. Age, gender, education, disability, seizure frequency, and psychiatric diagnoses were similar in patients with valid vs. invalid TOMM scores. Conclusions: Inadequate effort on PVTs was found in a minority of Veterans with verified PNES or ES (11-18% of patients). (2) Invalid PVTs were not significantly overrepresented in Veterans diagnosed with PNES vs. ES. (3) Patients with invalid PVTs had worse performance on cognitive tests, lower QOL scores, and greater PTSD and depression symptom complaints, as compared to patients with valid PVTs. The results suggest that patients with inadequate effort on PVTs often provide invalid data of limited value, and are not representative of the majority of Veterans with PNES or ES. PNES and ES treatment trials may benefit from segregating data obtained from patients with invalid PVTs. Funding: Funded by the Dept. of Veterans Affairs