title: Postictal ammonia as a biomarker for electrographic convulsive seizures: A prospective study.
abstract: Transient hyperammonemia (THA) was reported to follow generalized convulsions without sufficient evidence to confirm the epileptic nature of those events. We aimed to determine if postictal THA can differentiate between different types of events as confirmed electroencephalographically using video-electroencephalography (vEEG) monitoring.
  
  
  
  In our prospective cohort, we screened all consented adults (>18 years) admitted to the epilepsy monitoring unit. Ammonia was checked at baseline, within 60 min of the event (for all patients) and 24 h after event (whenever possible). Patients were grouped into generalized convulsive seizures (GCS), psychogenic nonepileptic seizures with convulsions (PNES-C), or focal seizures (FS) based on vEEG. Data were analyzed using descriptive statistics and parametric/nonparametric methods.
  
  
  
  Of 78 patients enrolled, 13 had GCS, 8 had FS, and 9 had PNES-C. The groups were different with regard to gender (p = 0.04) and baseline ammonia (p = 0.02), but not age. The change in ammonia postictally from baseline was significantly different among the three groups (p = 0.004). The area under the receiver operator characteristic (ROC) curve for postictal ammonia to distinguish GCS from other groups was 0.88 (95% confidence interval [CI] 0.69-0.96) suggesting ammonia to be a good test differentiating epileptic GCS from other events. An ammonia level of ≥80 μmol/L correctly classified 80% of our patients (sensitivity 53.9%, specificity 100%).
  
  
  
  Our results provide objective evidence for the association between THA and GCS seizures utilizing vEEG monitoring, and a basis for future studies to determine the role of postictal ammonia as an inexpensive diagnostic test to diagnose GCS.
authors.affiliation: Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, U.S.A.
authors.forename: Rawan
authors.initials: R
authors.lastname: Albadareen
authors.affiliation: Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, U.S.A.
authors.forename: Gary
authors.initials: G
authors.lastname: Gronseth
authors.affiliation: Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, U.S.A.
authors.forename: Patrick
authors.initials: P
authors.lastname: Landazuri
authors.affiliation: Department of Biostatistics, University of Kansas Medical Center, Kansas City, Kansas, U.S.A.
authors.forename: Jianghua
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, U.S.A.
authors.forename: Nancy
authors.initials: N
authors.lastname: Hammond
authors.affiliation: Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, U.S.A.
authors.forename: Utku
authors.initials: U
authors.lastname: Uysal
mesh_terms: D000328:Adult; D000641:Ammonia / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D015331:Cohort Studies; D004569:Electroencephalography; D005260:Female; D006801:Humans; D022124:Hyperammonemia / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012640:Seizures / Q000150:complications* / Q000378:metabolism*; D014741:Video Recording; D055815:Young Adult
chemical_list: D015415:Biomarkers; D000641:Ammonia
keywords: Ammonia; Convulsive seizures; Nonepileptic convulsions; Postictal hyperammonemia; Sensitivity and specificity