title: Medically intractable, localization-related epilepsy with normal MRI: presurgical evaluation and surgical outcome in 43 patients.
abstract: OBJECTIVE
  High-resolution magnetic resonance imaging (MRI) plays a crucial role in the presurgical evaluation of patients with medically refractory partial epilepsy. Although MRI detects a morphologic abnormality as the cause of the epilepsy in the majority of patients, some patients have a normal MRI. This study was undertaken to explore the hypothesis that in patients with normal MRI, invasive monitoring can lead to localization of the seizure-onset zone and successful epilepsy surgery.
  
  
  METHODS
  A series of 115 patients with partial epilepsy who had undergone intracranial electrode evaluation (subdural strip, subdural grid, and/or depth electrodes) between February 1992 and February 1999 was analyzed retrospectively. Of these, 43 patients (37%) had a normal MRI.
  
  
  RESULTS
  Invasive monitoring detected a focal seizure onset in 25 (58%) patients, multifocal seizure origin in 12 (28%) patients, and in six patients, no focal seizure origin was found. Of the 25 patients with a focal seizure origin, cortical resection was performed in 24, of whom 20 (83%) had a good surgical outcome with respect to seizure control. Six of the 12 patients with multifocal seizure origin underwent other forms of epilepsy surgery (palliative cortical resection in two, anterior callosotomy in two, and vagal nerve stimulator placement in two).
  
  
  CONCLUSIONS
  Successful epilepsy surgery is possible in patients with normal MRIs, but appropriate presurgical evaluations are necessary. In patients with evidence of multifocal seizure origin during noninvasive evaluation, invasive monitoring should generally be avoided.
authors.affiliation: Section of Neurology, Department of Pathology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Siegel
authors.forename: B C
authors.initials: BC
authors.lastname: Jobst
authors.forename: V M
authors.initials: VM
authors.lastname: Thadani
authors.forename: C H
authors.initials: CH
authors.lastname: Rhodes
authors.forename: P J
authors.initials: PJ
authors.lastname: Lewis
authors.forename: D W
authors.initials: DW
authors.lastname: Roberts
authors.forename: P D
authors.initials: PD
authors.lastname: Williamson
mesh_terms: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000473:pathology / Q000601:surgery*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000706:statistics & numerical data; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery*; D017034:Epilepsy, Frontal Lobe / Q000175:diagnosis / Q000601:surgery; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D012189:Retrospective Studies; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon / Q000706:statistics & numerical data; D016896:Treatment Outcome
chemical_list: D019690:Technetium Tc 99m Exametazime