title: Resected Brain Tissue, Seizure Onset Zone and Quantitative EEG Measures: Towards Prediction of Post-Surgical Seizure Control.
abstract: BACKGROUND
  Epilepsy surgery is a potentially curative treatment option for pharmacoresistent patients. If non-invasive methods alone do not allow to delineate the epileptogenic brain areas the surgical candidates undergo long-term monitoring with intracranial EEG. Visual EEG analysis is then used to identify the seizure onset zone for targeted resection as a standard procedure.
  
  
  METHODS
  Despite of its great potential to assess the epileptogenicty of brain tissue, quantitative EEG analysis has not yet found its way into routine clinical practice. To demonstrate that quantitative EEG may yield clinically highly relevant information we retrospectively investigated how post-operative seizure control is associated with four selected EEG measures evaluated in the resected brain tissue and the seizure onset zone. Importantly, the exact spatial location of the intracranial electrodes was determined by coregistration of pre-operative MRI and post-implantation CT and coregistration with post-resection MRI was used to delineate the extent of tissue resection. Using data-driven thresholding, quantitative EEG results were separated into normally contributing and salient channels.
  
  
  RESULTS
  In patients with favorable post-surgical seizure control a significantly larger fraction of salient channels in three of the four quantitative EEG measures was resected than in patients with unfavorable outcome in terms of seizure control (median over the whole peri-ictal recordings). The same statistics revealed no association with post-operative seizure control when EEG channels contributing to the seizure onset zone were studied.
  
  
  CONCLUSIONS
  We conclude that quantitative EEG measures provide clinically relevant and objective markers of target tissue, which may be used to optimize epilepsy surgery. The finding that differentiation between favorable and unfavorable outcome was better for the fraction of salient values in the resected brain tissue than in the seizure onset zone is consistent with growing evidence that spatially extended networks might be more relevant for seizure generation, evolution and termination than a single highly localized brain region (i.e. a "focus") where seizures start.
authors.affiliation: Support Center for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Rummel
authors.affiliation: Support Center for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern, Switzerland; Department of Neurology, Inselspital, Bern, Switzerland.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Abela
authors.affiliation: Universitat Pompeu Fabra, Department of Information and Communication Technologies, Barcelona, Spain.
authors.forename: Ralph G
authors.initials: RG
authors.lastname: Andrzejak
authors.affiliation: Bethesda Epilepsy Clinic, Tschugg, Switzerland; Support Center for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern, Switzerland.
authors.forename: Martinus
authors.initials: M
authors.lastname: Hauf
authors.affiliation: Department of Neurosurgery, Inselspital, Bern, Switzerland.
authors.forename: Claudio
authors.initials: C
authors.lastname: Pollo
authors.affiliation: Centro de Investigaciones en Ciencias, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico; Centro Internacional de Ciencias, Universidad Autónoma de México, Cuernavaca, Mexico.
authors.forename: Markus
authors.initials: M
authors.lastname: Müller
authors.affiliation: Support Center for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Weisstanner
authors.affiliation: Support Center for Advanced Neuroimaging (SCAN), University Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Wiest
authors.affiliation: Department of Neurology, Inselspital, Bern, Switzerland.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Schindler
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology* / Q000601:surgery*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012189:Retrospective Studies; D012640:Seizures / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy*; D014057:Tomography, X-Ray Computed; D055815:Young Adult