title: Postictal immobility and generalized EEG suppression are associated with the severity of respiratory dysfunction.
abstract: OBJECTIVE
  The pathophysiology of sudden unexpected death in epilepsy (SUDEP) remains undetermined. Seizures are accompanied by respiratory dysfunction (RD). Postictal generalized electroencephalography (EEG) suppression (PGES) may follow generalized tonic-clonic seizures (GTCS). Following GTCS patients have impaired arousal and may be motionless. Patients with SUDEP are usually prone. Postictal immobility (PI) may contribute to SUDEP by not permitting repositioning of the head to allow unimpeded ventilation. To determine whether RD and/or ictal characteristics are associated with PI, we analyzed patients with GTCS in the epilepsy monitoring unit.
  
  
  METHODS
  We investigated for associations between PI duration and PGES, ictal/postictal oxygen saturation (SpO2 ), end-tidal CO2 (ETCO2 ), seizure localization, duration, and tonic and total convulsive phase duration. We investigated for linkage between PGES and these measures.
  
  
  RESULTS
  Seventy patients with 181 GTCS and available SpO2 and/or ETCO2 data were studied. Simple linear regression analysis by seizures showed that PI duration was associated with peak periictal ETCO2 (p = 0.03), duration of oxygen desaturation (p = 0.005) and with SpO2 nadir (p = 0.02). PI duration was not associated with tonic, convulsive phase or total seizure duration. Analysis by patients also showed significant association of PI with RD. Duration of PI was longer following seizures with PGES (p < 0.001). PGES was not associated with the tonic, convulsive phase or total seizure duration. SpO2 nadir was lower in seizures with PGES (p = 0.046), ETCO2 peak change (p = 0.003) was higher, and duration of ETCO2 elevation (p = 0.03) was longer. Multivariable regression analysis showed that PGES and severe RD were associated with PI duration.
  
  
  CONCLUSIONS
  The duration of PI and presence of PGES are associated with periictal RD. The duration of PI is also associated with the presence of PGES. Seizure duration or duration of the convulsive phase is not associated with PI or PGES. Interventions aimed at reversing impaired arousal and PI may reduce SUDEP risk.
authors.affiliation: Department of Neurology, University of California, Davis, California, U.S.A.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Kuo
authors.affiliation: Department of Statistics, University of California, Davis, California, U.S.A.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Division of Biostatistics, Department of Public Health Sciences, University of California, Davis, California, U.S.A.
authors.forename: Chin-Shang
authors.initials: CS
authors.lastname: Li
authors.affiliation: Department of Neurology, University of California, Davis, California, U.S.A.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Kennedy
authors.affiliation: Department of Neurology, University of California, Davis, California, U.S.A.
authors.forename: Masud
authors.initials: M
authors.lastname: Seyal
mesh_terms: D000328:Adult; D003645:Death, Sudden / Q000453:epidemiology; D004569:Electroencephalography / Q000379:methods*; D004830:Epilepsy, Tonic-Clonic / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012120:Respiration Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D012720:Severity of Illness Index; D055815:Young Adult
keywords: Convulsion; Postictal generalized EEG suppression; Postictal immobility; Respiratory dysfunction; Seizure; Sudden unexpected death in epilepsy