title: Comparing noninvasive dense array and intracranial electroencephalography for localization of seizures.
abstract: OBJECTIVE
  To compare the localization of the seizure onset zone estimated from ictal recordings with high spatial resolution, 256-channel scalp dense array electroencephalographic video long-term monitoring (LTM) with the aid of source analysis with that obtained from subsequent intracranial ictal recordings.
  
  
  METHODS
  Ten patients with medically refractory epilepsy, all surgical candidates, underwent intracranial LTM after standard noninvasive evaluation failed to provide adequate localizing information regarding ictal origins. Before invasive studies, all patients underwent dense array electroencephalographic LTM in which habitual clinical seizures were recorded for each patient. Source analysis was applied to ictal onsets. Intracranial electrode placement followed conventional guidelines, although the neurosurgeon was aware of the dense array electroencephalographic results. Patients ranged in age from 10 to 49 years (mean age, 24 y); 7 were male. Identified risk factors included closed head injury in 1 patient and childhood meningitis in another. No focal neurological signs were found in any patient. Magnetic resonance imaging findings were normal in 6 patients; 1 patient had cerebellar hypoplasia, 1 had right frontoparietal dysplasia, 1 had bilateral nonspecific white matter abnormalities, and 1 had bilateral cavernous angiomas.
  
  
  RESULTS
  Ictal onsets, based on invasive recordings, were in the mesiotemporal lobe (3 patients), lateroparietal (2 patients), mesioparietal (1 patient), laterofrontal (1 patient), superolateral frontocentral (1 patient), frontopolar (1 patient), and posteroinferior temporo-occipital neocortex (1 patient). Dense array electroencephalography localized ictal onsets to the same region as intracranial monitoring in 8 of 10 cases; invasive studies disclosed an additional ictal focus in 2 of these patients. Surgical resections were based only on intracranial electroencephalographic findings.
  
  
  CONCLUSIONS
  Dense array electroencephalography has the potential to assist in the noninvasive localization of epileptic seizures and to guide the placement of invasive electrodes for localizing seizure onset.
authors.affiliation: Regional Epilepsy Center, Department of Neurology, University of Washington, Seattle, Washington 98104, USA. mdholmes@u.washington.edu
authors.forename: Mark D
authors.initials: MD
authors.lastname: Holmes
authors.forename: Don M
authors.initials: DM
authors.lastname: Tucker
authors.forename: Jason M
authors.initials: JM
authors.lastname: Quiring
authors.forename: Shahin
authors.initials: S
authors.lastname: Hakimian
authors.forename: John W
authors.initials: JW
authors.lastname: Miller
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Ojemann
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000295:instrumentation / Q000379:methods*; D002648:Child; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D012535:Scalp; D012640:Seizures / Q000175:diagnosis* / Q000503:physiopathology*; D014742:Videodisc Recording / Q000379:methods; D055815:Young Adult