title: A longitudinal study of surgical outcome and its determinants following posterior cortex epilepsy surgery.
abstract: OBJECTIVE
  To investigate the longitudinal seizure outcome and identify potential prognostic indicators following posterior cortex epilepsy (PCE) surgery.
  
  
  METHODS
  We reviewed patients who underwent a parietal, occipital, or parietooccipital resections between 1994 and 2006, using survival analysis and multivariate regression with Cox proportional hazard modeling. A favorable outcome was defined as Engel Class I at last follow-up.
  
  
  RESULTS
  Fifty-seven patients were identified with a mean follow-up of 3.3 years (range 1-12 years). The estimated chance of seizure freedom (SF) was 73.1% at 6 postoperative months, 68.5% at 1 year, 65.8% at between 2 and 5 years, and 54.8% at 6 years and beyond. Most recurrences (75%) occurred within the first 6 postoperative months. Parietal resections had a worse outcome than occipital or parietooccipital resections (52% SF vs. 89% and 93%, respectively, at 5 years). Independent predictors of recurrence included an epilepsy etiology other than tumor or dysplasia [risk ratio (RR) 2.29], limiting resection to a lesionectomy (RR 2.10), having ipsilateral temporal spiking on preoperative scalp electroencephalography (EEG) (RR 2.06), or any ipsilateral spiking on postoperative EEG (RR 2.70) (Log likelihood-ratio test p < 0.0001). Only 40-50% of patients with a poor outcome predictor were SF at 5 postoperative years as opposed to about 80% otherwise. In surgical failures, recurrent seizure frequency was related directly to baseline seizure frequency and to the presence of ipsilateral spiking on postoperative EEG.
  
  
  CONCLUSIONS
  These data highlight favorable long-term outcomes following PCE surgery. Limited surgical resection and diffuse baseline epileptogenicity may be important predictors of seizure recurrence.
authors.affiliation: Department of Neurology, Epilepsy Center, Cleveland Clinic, Cleveland, Ohio 44195, USA. jehil@ccf.org
authors.forename: Lara E
authors.initials: LE
authors.lastname: Jehi
authors.forename: Rebecca
authors.initials: R
authors.lastname: O'Dwyer
authors.forename: Imad
authors.initials: I
authors.lastname: Najm
authors.forename: Andreas
authors.initials: A
authors.lastname: Alexopoulos
authors.forename: William
authors.initials: W
authors.lastname: Bingaman
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology / Q000601:surgery*; D004569:Electroencephalography / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D019635:Neurosurgical Procedures; D011300:Preoperative Care; D011379:Prognosis; D016016:Proportional Hazards Models; D012008:Recurrence; D016019:Survival Analysis; D016896:Treatment Outcome