title: Epileptiform abnormalities predict delayed cerebral ischemia in subarachnoid hemorrhage.
abstract: To identify whether abnormal neural activity, in the form of epileptiform discharges and rhythmic or periodic activity, which we term here ictal-interictal continuum abnormalities (IICAs), are associated with delayed cerebral ischemia (DCI).
  
  
  
  Retrospective analysis of continuous electroencephalography (cEEG) reports and medical records from 124 patients with moderate to severe grade subarachnoid hemorrhage (SAH). We identified daily occurrence of seizures and IICAs. Using survival analysis methods, we estimated the cumulative probability of IICA onset time for patients with and without delayed cerebral ischemia (DCI).
  
  
  
  Our data suggest the presence of IICAs indeed increases the risk of developing DCI, especially when they begin several days after the onset of SAH. We found that all IICA types except generalized rhythmic delta activity occur more commonly in patients who develop DCI. In particular, IICAs that begin later in hospitalization correlate with increased risk of DCI.
  
  
  
  IICAs represent a new marker for identifying early patients at increased risk for DCI. Moreover, IICAs might contribute mechanistically to DCI and therefore represent a new potential target for intervention to prevent secondary cerebral injury following SAH.
  
  
  
  These findings imply that IICAs may be a novel marker for predicting those at higher risk for DCI development.
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Kim
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: E S
authors.initials: ES
authors.lastname: Rosenthal
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Biswal
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zafar
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Shenoy
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: O'Connor
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Bechek
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: J
authors.initials: J
authors.lastname: Valdery Moura
authors.affiliation: Beth Israel Deaconess Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Shafi
authors.affiliation: Massachusetts General Hospital, Department of Neurosurgery, Harvard Medical School Boston, MA, USA.
authors.forename: A B
authors.initials: AB
authors.lastname: Patel
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Cash
authors.affiliation: Massachusetts General Hospital, Department of Neurology, Harvard Medical School Boston, MA, USA. Electronic address: mwestover@mgh.harvard.edu.
authors.forename: M B
authors.initials: MB
authors.lastname: Westover
mesh_terms: D002545:Brain Ischemia / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D058256:Brain Waves; D004827:Epilepsy / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D010507:Periodicity; D013345:Subarachnoid Hemorrhage / Q000150:complications* / Q000175:diagnosis
keywords: Continuous EEG monitoring; Cortical spreading depolarization; Delayed cerebral ischemia; Epileptiform discharges; Ictal-interictal continuum; Subarachnoid hemorrhage