title: Focal cortical dysplasia type IIb: completeness of cortical, not subcortical, resection is necessary for seizure freedom.
abstract: OBJECTIVE
  Focal cortical dysplasia type IIb (FCD IIb) lesions are highly epileptogenic and frequently cause pharmacoresistant epilepsy. Complete surgical resection leads to seizure freedom in most cases. However, the term "complete" resection is controversial with regard to the necessity of performing resections of the subcortical zone, which is frequently seen in these lesions on magnetic resonance imaging (MRI).
  
  
  METHODS
  We retrospectively analyzed 50 epilepsy patients with histologically proven FCD IIb. The extent of surgical resection was determined by SPM5-based coregistration of the preoperative and postoperative MRI scans. Postoperative outcome was analyzed with regard to (1) the completeness of the resection of the cortical abnormality and (2) the completeness of the resection of the subcortical abnormality.
  
  
  RESULTS
  Complete resection of the cortical abnormality led to postoperative seizure freedom (Engel class Ia) in 34 of 37 patients (92%), whereas incomplete cortical resection achieved this in only one of 13 patients (8%, p < 0.001). Among the patients with complete cortical resection, 36 had FCDs with a subcortical hyperintensity according to MRI. In this group, complete resection of the subcortical abnormality did not result in a better postoperative outcome than incomplete resection (90% vs. 93% for Engel class Ia, n.s.).
  
  
  CONCLUSIONS
  Complete resection of the MRI-documented cortical abnormality in FCD IIb is crucial for a favorable postoperative outcome. However, resection of the subcortical hyperintense zone is not essential for seizure freedom. Therefore, sparing of the subcortical white matter may reduce the surgical risk of encroaching on relevant fiber tracts. In addition, these findings give an interesting insight into the epileptogenic propensity of different parts of these lesions.
authors: Department of Epileptology, University of Bonn, Bonn, Germany. jan.wagner@ukb.uni-bonn.de
authors: Jan
authors: J
authors: Wagner
authors: Horst
authors: H
authors: Urbach
authors: Pitt
authors: P
authors: Niehusmann
authors: Marec
authors: M
authors: von Lehe
authors: Christian E
authors: CE
authors: Elger
authors: Jörg
authors: J
authors: Wellmer
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology / Q000601:surgery*; D002540:Cerebral Cortex / Q000473:pathology / Q000601:surgery*; D018572:Disease-Free Survival; D004351:Drug Resistance; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis / Q000473:pathology / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D054220:Malformations of Cortical Development / Q000175:diagnosis / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods; D016896:Treatment Outcome