title: Termination of seizure clusters is related to the duration of focal seizures.
abstract: Clustered seizures are characterized by shorter than usual interseizure intervals and pose increased morbidity risk. This study examines the characteristics of seizures that cluster, with special attention to the final seizure in a cluster.
  
  
  
  This is a retrospective analysis of long-term inpatient monitoring data from the EPILEPSIAE project. Patients underwent presurgical evaluation from 2002 to 2009. Seizure clusters were defined by the occurrence of at least two consecutive seizures with interseizure intervals of <4 h. Other definitions of seizure clustering were examined in a sensitivity analysis. Seizures were classified into three contextually defined groups: isolated seizures (not meeting clustering criteria), terminal seizure (last seizure in a cluster), and intracluster seizures (any other seizures within a cluster). Seizure characteristics were compared among the three groups in terms of duration, type (focal seizures remaining restricted to one hemisphere vs. evolving bilaterally), seizure origin, and localization concordance among pairs of consecutive seizures.
  
  
  
  Among 92 subjects, 77 (83%) had at least one seizure cluster. The intracluster seizures were significantly shorter than the last seizure in a cluster (p = 0.011), whereas the last seizure in a cluster resembled the isolated seizures in terms of duration. Although focal only (unilateral), seizures were shorter than seizures that evolved bilaterally and there was no correlation between the seizure type and the seizure position in relation to a cluster (p = 0.762). Frontal and temporal lobe seizures were more likely to cluster compared with other localizations (p = 0.009). Seizure pairs that are part of a cluster were more likely to have a concordant origin than were isolated seizures. Results were similar for the 2 h definition of clustering, but not for the 8 h definition of clustering.
  
  
  
  We demonstrated that intracluster seizures are short relative to isolated seizures and terminal seizures. Frontal and temporal lobe seizures are more likely to cluster.
authors.affiliation: Department of Neurology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York, U.S.A.|Comprehensive Epilepsy Management Center, Montefiore Medical Center, Bronx, New York, U.S.A.
authors.forename: Victor
authors.initials: V
authors.lastname: Ferastraoaru
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schulze-Bonhage
authors.affiliation: Department of Neurology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York, U.S.A.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Lipton
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Dümpelmann
authors.affiliation: Department of Neurology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York, U.S.A.|Comprehensive Epilepsy Management Center, Montefiore Medical Center, Bronx, New York, U.S.A.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Legatt
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, Freiburg, Germany.|Department of Neuropediatrics and Muscle Disorders, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Julie
authors.initials: J
authors.lastname: Blumberg
authors.affiliation: Department of Neurology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York, U.S.A.|Comprehensive Epilepsy Management Center, Montefiore Medical Center, Bronx, New York, U.S.A.
authors.forename: Sheryl R
authors.initials: SR
authors.lastname: Haut
mesh_terms: D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D016000:Cluster Analysis; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012640:Seizures / Q000473:pathology / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: Clustering effect; Repetitive seizures; Seizure cluster; Seizure duration; Seizure localization