Abstracts

Rationale: Anion gap metabolic acidosis (AGMA) following generalized tonic colonic seizures (GTC) has been observed in prior case studies. Recent work has also shown that evaluating AGMA within a larger framework (the Denver Seizure Score (DSS)) could help distinguish syncope from GTC. In this study we investigate whether AGMA can be used to differentiate between GTC, complex partial seizures (CP), and nonepileptic seizures (NES) with generalized shaking semiology. Methods: Retrospective chart review was conducted to identify patients older than 18 who visited the University of Massachusetts Medical School in 2015 for evaluation of seizures within 24 hours after seizure onset. Patients with active medical problems that could also cause acidosis and would confound the analysis of the study were excluded. Results: Nine hundred fifty nine records were screened and 156 patients were recruited based on criteria above. Of these, 89 patients were in the GTC group. Five patients were tested with basic metabolic panel (BMP) within 0.5 hr of seizure onset, showing average carbon dioxide (CO2) level of 21+/-4.8 mmol/L, average anion gap (AG) of 12.5+/-5.3, and average DSS of 8.8. Thirteen patients were tested in 0.5 to 1hr, showing average CO2 level of 19.9+/-5.2 mmol/L, average AG of 15.5+/-5.6, and average DSS of 11. Twenty-five patients were tested in1-2 hours of onset, showing average CO2 level of 23.1+/-4.9 mmol/L, average AG of 10.2+/-4.7, and average DSS of -2.8. Twenty patients were tested within 6-24hr, showing average CO2 level of 25+/-7.5mmol/L, average AG of 7.5+/-2.4, and average DSS of -9.5. Sixty three patients were in the CP group. One patient was tested in 0.5 hr of onset, showing CO2 level of 27, AG of 8, and DSS of -11. 6 patients were tested in 0.5-1 hr, showing average CO2 level of 23.8+/-4.1 mmol/L, average AG of 8.7 +/-3.3, and average DSS of -6.5. Eighteen patients were tested in 1-2 hr, showing average CO2 level of 24.8+/-2.8 mmol/L, average AG of 8.4+/-4.5, and average DSS of -7.9. 15 patients were tested in 6-24hr, showing average CO2 level of 25.1+/-4.0 mmol/L, average AG of 8.1+/-2.2, and average DSS of -8.9. Four patients were in the NES group. Two patients were tested with BMP within 2-3 hr of seizure onset, showing average CO2 level of 16+/-15.6 mmol/L, average AG of 4.5+/-0.7, and average DSS of -7. 2 patients were tested in 6-24hr, showing average CO2 level of 25+/-1.1 mmol/L, average AG of 3+/-1.4, and average DSS of -19. Conclusions: Consistent AGMA is observed soon after GTC seizures, with CO2 level reaching the nadir between 0.5-1hrs. Fifty two percent of patients return back to normal level by 2 hours after seizure onset. This phenomenon is not seen in NES or CP groups. DSS could be a potentially useful tool to differentiate NES or CP seizures from GTC seizures, when the patient is evaluated within 2 hours of the seizure onset. Funding: N/A