Abstracts

Rationale: Evaluation of shaking spells are frequently encountered questions by neurologists. Differentiation between PNES and GTCS is important for appropriate triaging in the emergency department (ED), however it can be difficult, especially if not witnessed.  Transient acidosis and transient leukocytosis have both been noted following convulsive seizures. Whether they could be helpful to differentiate between PNES and GTCS in the emergency setting has not been investigated yet. Hence in the current study, we investigated whether Anion gap (AG), bicarbonate, and leukocytosis could differentiate between psychogenic non-epileptic seizures (PNES) and generalized convulsive epileptic seizures (GTCS) in the emergency setting. Methods: In total, 1354 patients who were admitted to ED due to generalized shaking spells in a tertiary care medical center from 1/2014- 6/2016 were screened. Patients were excluded from the study if they had other documented active medical problems which could cause acidosis and confound the analysis, such as sepsis, alcohol or medicine toxicity; or did not have lab studies within 24 hours after their spell. 27 PNES and 27 GTCS patients were identified based on clinical description and subsequent EEG. Pearson correlation study, multivariable logistic regression analysis and receiver operating characteristic curves were used to determine whether there was an association between AG, bicarbonate, or WBC count drawn within 24 hours of the concerning event. Results: The value of AG, bicarbonate and leukocytosis are correlated with diagnosis of the PNES vs. GTCS (p ‹ 0.05). Transient leukocytosis seen after these events became more prominent over time with the mean value peak from 4-6 hours. After six hours, the mean value of the WBC gradually came back to normal range.  In the first 6 hours, with the cutoff of abnormal WBC value at 10.4, this value has 100% specificity with sensitivity of 55.6%. For AG and bicarbonate, the sensitivity and specificity dropped markedly for all measures if drawn more than 2 hours after the event, and AG was more sensitive than bicarbonate for GTCS. With the cutoff of AG greater than 10, it has sensitivity of 81.8% and specificity of 100% in the first two hours after the event. Overall the value of the area under ROC curve of AG (0.815) is higher than both WBC (0.688) and bicarbonate (0.686) in the first 24 hours after the event. Conclusions: AG has a higher sensitivity and negative predictive value than leukocytosis and bicarbonate, however the leukocytosis peak is later than the AG. It is possible that these values may both be useful tools to help distinguishing between these conditions depending on the timing of the event and subsequent presentation to the ED. Further study will be needed to validate these on a prospective basis. Funding: None