title: The delta between postoperative seizure freedom and persistence: Automatically detected focal slow waves after epilepsy surgery.
abstract: In this study, we use a novel automated method for localization and quantitative comparison of magnetoencephalographic (MEG) delta activity in patients with and without recurrent seizures after epilepsy surgery as well as healthy controls.
  
  
  
  We identified the generators of delta activity by source location in frequency domain between 1 and 4 Hz in spontaneous MEG data. Comparison with healthy control subjects by z-transform emphasized relative changes of activation in patients. The individual results were compared to spike localizations and statistical group analysis was performed. Additionally, MEG results were compared to 1-4 Hz activity in invasive EEG (iEEG) in two patients, in whom this data was available.
  
  
  
  Patients with recurrent seizures exhibited significantly increased focal MEG delta activity both in comparison to healthy controls and seizure free patients. This slow activity showed a correlation to interictal epileptic activity and was not explained by consequences of the resection alone. In two patients with iEEG, iEEG analysis was concordant with the MEG findings.
  
  
  
  The quantity of delta activity could be used as a diagnostic marker for recurrent seizures. The close relation to epileptic spike localizations and the resection volume of patients with successful second surgery imply involvement in seizure recurrence. This initial evidence suggests a potential application in the planning of second epilepsy surgery.
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Margit
authors.initials: M
authors.lastname: Schönherr
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Stefan
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Hajo M
authors.initials: HM
authors.lastname: Hamer
authors.affiliation: Department of Neurosurgery, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Karl
authors.initials: K
authors.lastname: Rössler
authors.affiliation: Department of Neurosurgery, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Buchfelder
authors.affiliation: Department of Neurosurgery, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rampp
mesh_terms: D000293:Adolescent; D000328:Adult; D003700:Delta Rhythm / Q000502:physiology*; D000069280:Electrocorticography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D012008:Recurrence; D012640:Seizures / Q000503:physiopathology* / Q000601:surgery; D055815:Young Adult
keywords: Delta activity; Epilepsy; Persisting seizures; Surgery