title: Seizure occurrence and the circadian rhythm of cortisol: a systematic review.
abstract: OBJECTIVE
  Stress is the seizure precipitant most often reported by patients with epilepsy or their caregivers. The relation between stress and seizures is presumably mediated by stress hormones such as cortisol, affecting neuronal excitability. Endogenous cortisol is released in a circadian pattern. To gain insight into the relation between the circadian rhythm of cortisol and seizure occurrence, we systematically reviewed studies on the diurnal distribution of epileptic seizures in children and adults and linked the results to the circadian rhythm of cortisol.
  
  
  METHODS
  A structured literature search was conducted to identify relevant articles, combining the terms 'epilepsy' and 'circadian seizure distribution', plus synonyms. Articles were screened using predefined selection criteria. Data on 24-hour seizure occurrence were extracted, combined, and related to a standard circadian rhythm of cortisol.
  
  
  RESULTS
  Fifteen relevant articles were identified of which twelve could be used for data aggregation. Overall, seizure occurrence showed a sharp rise in the early morning, followed by a gradual decline, similar to cortisol rhythmicity. The occurrence of generalized seizures and focal seizures originating from the parietal lobe in particular followed the circadian rhythm of cortisol.
  
  
  CONCLUSIONS
  The diurnal occurrence of epileptic seizures shows similarities to the circadian rhythm of cortisol. These results support the hypothesis that circadian fluctuations in stress hormone level influence the occurrence of epileptic seizures.
authors.affiliation: Department of Pediatric Neurology, University Medical Center Utrecht, The Netherlands; Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, The Netherlands. Electronic address: J.S.vanCampen@gmail.com.
authors.forename: Jolien S
authors.initials: JS
authors.lastname: van Campen
authors.affiliation: Department of Pediatric Neurology, University Medical Center Utrecht, The Netherlands.
authors.forename: Floris A
authors.initials: FA
authors.lastname: Valentijn
authors.affiliation: Department of Pediatric Neurology, University Medical Center Utrecht, The Netherlands.
authors.forename: Floor E
authors.initials: FE
authors.lastname: Jansen
authors.affiliation: Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, The Netherlands.
authors.forename: Marian
authors.initials: M
authors.lastname: Joëls
authors.affiliation: Department of Pediatric Neurology, University Medical Center Utrecht, The Netherlands.
authors.forename: Kees P J
authors.initials: KP
authors.lastname: Braun
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D004827:Epilepsy; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D012640:Seizures / Q000453:epidemiology / Q000503:physiopathology*
chemical_list: D006854:Hydrocortisone
keywords: Chronobiology; Diurnal; Epilepsy; Hormones; Stress