Abstracts

Rationale: Psychogenic non-epileptic events (PNEE) represent paroxysmal behaviors that are caused by heterogeneous psychopathological processes rather than epileptic neuronal discharges. Three major groups of PNEE based on ictal semiology are hypermotor, hypomotor and experiential groups. Several investigators have supported the use of induction techniques for provocation of habitual PNEE of relevance, reporting success rates in the range of 77 to 84%. We hypothesize that the success rate of induction varies with ictal semiology of the presenting event of interest. Secondly, we hypothesize that neuropsychological profiles and/or demographic factors may influence the success rate of induction. Methods: We enrolled veterans admitted to the epilepsy monitoring unit at the Michael E. DeBakey VA Medical Center from December 2008 until April 2010. Patients with epilepsy or mixed disorder of epilepsy and PNEE were excluded. According to the routine protocol at this center, provocative techniques such as photic stimulation, hyperventilation, and placebo injection are used for induction of events of interest in patients without a spontaneous event during the first 48 hours. The events of interest were categorized into three groups based on the semiologic features mentioned above. Most of the patients also completed 4 neuropsychological questionnaires: Dissociative Expressive Scale (DES), Structured Inventory of Malingered Symptomatology (SIMS), Test of Memory Malingering (TOMM), and brief COPE inventory. Results: Demographic data of the 51 patients who were included in the analysis and their final categorization based on semiology of their event of interest is shown in the table. 24 out of 26 (92.3%) patients in the hypermotor category had successful induction of their habitual event of interest, leading to definitive diagnoses of PNEE. On the other hand, only 13 out of 20 (65%) patients in the hypomotor category had successful induction (p=0.029) (figure). Due to the small number of patients in the experiential group (n=5), the inductive success rate in this group could not be confidently assessed. Demographic and neuropsychological data were compared between the successful induction and unsuccessful induction groups. The main significant difference was the higher percentage of patients who had a SIMS score of more than 14 in the successful induction group compared to the unsuccessful induction group (p=0.035). Conclusions: We observed that induction techniques were statistically more likely to provoke hypermotor PNEE as compared to hypomotor PNEE (p = 0.029). It can be possible that our hypomotor cases represented a wider spectrum of etiologies, including epileptic, physiologic non-epileptic, feigned, or other events not typically known to demonstrate suggestibility. Such etiologic diversity may in part explain the diminished induction success rate for hypomotor events. We observed a significant association of elevated SIMS score (> 14) among successfully induced cases, which may support the tendency toward over-reporting or exaggeration of symptoms among inducible patients.