title: Long-term epilepsy surgery outcomes in patients with MRI-negative temporal lobe epilepsy.
abstract: OBJECTIVE
  The outcome of surgery in patients with temporal lobe epilepsy (TLE) and normal high-resolution magnetic resonance imaging (MRI) has been significantly worse than in patients with unilateral hippocampal damage upon MRI. The purpose of this study was to determine the long-term outcomes of consecutive true MRI-negative TLE patients who all underwent standardized preoperative evaluation with intracranial electroencephalography (EEG) electrodes.
  
  
  METHODS
  In this study we present all adult MRI-negative TLE surgery candidates evaluated between January 1990 and December 2006 at Kuopio Epilepsy Center in Kuopio University Hospital, which provides a national center for epilepsy surgery in Finland. During this period altogether 146 TLE surgery candidates were evaluated with intracranial electrodes, of whom 64 patients with normal high-resolution MRI were included in this study.
  
  
  RESULTS
  Among the 38 patients who finally underwent surgery, at the latest follow-up (mean 5.8 years), 15 (40%) were free of disabling seizures (Engel class I) and 6 (16%) were seizure-free (Engel class IA). Twenty-one (55%) of 38 patients had poor outcomes (Engel class III-IV). Outcomes did not change compared to 12-month follow-up. Histopathologic examination failed to reveal any focal pathology in 68% of our MR-negative cases. Only patients with noncongruent positron emission tomography (PET) results had worse outcomes (p = 0.044).
  
  
  CONCLUSIONS
  Our results suggest that epilepsy surgery outcomes in MRI-negative TLE patients are comparable with extratemporal epilepsy surgery in general. Seizure outcomes in the long-term also remain stable. Modern imaging techniques could further improve the postsurgical seizure-free rate. However, these patients usually require chronic intracranial EEG evaluation to define epileptogenic areas.
authors.affiliation: Department of Neurosurgery, Kuopio University Hospital, Kuopio, Finland. Arto.Immonen@kuh.fi
authors.forename: Arto
authors.initials: A
authors.lastname: Immonen
authors.forename: Leena
authors.initials: L
authors.lastname: Jutila
authors.forename: Anu
authors.initials: A
authors.lastname: Muraja-Murro
authors.forename: Esa
authors.initials: E
authors.lastname: Mervaala
authors.forename: Marja
authors.initials: M
authors.lastname: Äikiä
authors.forename: Salla
authors.initials: S
authors.lastname: Lamusuo
authors.forename: Jyrki
authors.initials: J
authors.lastname: Kuikka
authors.forename: Esko
authors.initials: E
authors.lastname: Vanninen
authors.forename: Irina
authors.initials: I
authors.lastname: Alafuzoff
authors.forename: Aki
authors.initials: A
authors.lastname: Ikonen
authors.forename: Ritva
authors.initials: R
authors.lastname: Vanninen
authors.forename: Matti
authors.initials: M
authors.lastname: Vapalahti
authors.forename: Reetta
authors.initials: R
authors.lastname: Kälviäinen
mesh_terms: D000293:Adolescent; D000328:Adult; D038481:Anterior Temporal Lobectomy; D003072:Cognition Disorders / Q000175:diagnosis / Q000503:physiopathology; D004292:Dominance, Cerebral / Q000502:physiology; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005387:Finland; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D049268:Positron-Emission Tomography; D012815:Signal Processing, Computer-Assisted; D013702:Temporal Lobe / Q000503:physiopathology; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome; D014888:Wechsler Scales; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18