title: Neuroimaging characteristics of MRI-negative orbitofrontal epilepsy with focus on voxel-based morphometric MRI postprocessing.
abstract: OBJECTIVE
  The orbitofrontal (OF) region is one of the least explored regions of the cerebral cortex. There are few studies on patients with electrophysiologically and surgically confirmed OF epilepsy and a negative magnetic resonance imaging (MRI) study. We aimed to examine the neuroimaging characteristics of MRI-negative OF epilepsy with the focus on a voxel-based morphometric MRI postprocessing technique.
  
  
  METHODS
  We included six patients with OF epilepsy, who met the following criteria: surgical resection of the OF lobe with/without adjacent cortex, seizure-free for ≥12 months, invasive video-electroencephalography (EEG) monitoring showing ictal onset from the OF area, and preoperative MRI regarded as negative. Patients were investigated in terms of their image postprocessing and functional neuroimaging characteristics, electroclinical characteristics obtained from noninvasive and invasive evaluations, and surgical pathology. MRI postprocessing on T1 -weighted high-resolution scans was implemented with a morphometric analysis program (MAP) in MATLAB.
  
  
  RESULTS
  Single MAP+ abnormalities were found in four patients; three were in the OF region and one in the ipsilateral mesial frontal area. These abnormalities were included in the resection. One patient had bilateral MAP+ abnormalities in the OF region, with the ipsilateral one completely removed. The MAP+ foci were concordant with invasive electrophysiologic data in the majority of MAP+ patients (four of five). The localization value of 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) and ictal single-photon emission computed tomography (SPECT) is low in this cohort. Surgical pathology included focal cortical dysplasia, remote infarct, Rosenthal fiber formation and gliosis.
  
  
  CONCLUSIONS
  Our study highlights the importance of MRI postprocessing in the process of presurgical evaluation of patients with suspected orbitofrontal epilepsy and "normal" MRI. Using MAP, we were able to positively identify subtle focal abnormalities in the majority of the patients. MAP results need to be interpreted in the context of their electroclinical findings and can provide valuable targets in the process of planning invasive evaluation.
authors.affiliation: Cleveland Clinic Epilepsy Center.
authors.forename: Z Irene
authors.initials: ZI
authors.lastname: Wang
authors.affiliation: Epilepsy Center Neurology Clinic, Clinical Center of Serbia Dr Subotica 6, 11000 Belgrade, Serbia.
authors.forename: Aleksandar J
authors.initials: AJ
authors.lastname: Ristic
authors.affiliation: Department of Neurology, Westmead Hospital, Sydney, Australia.
authors.forename: Chong H
authors.initials: CH
authors.lastname: Wong
authors.affiliation: Diagnostic Radiology, Mellen Center, Cleveland Clinic.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Jones
authors.affiliation: Cleveland Clinic Epilepsy Center.
authors.forename: Imad M
authors.initials: IM
authors.lastname: Najm
authors.affiliation: Department of Neurology, Epilepsy Center, University of Greifswald, Greifswald, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Schneider
authors.affiliation: Epilepsy Center, Second Affiliated Hospital, Zhejiang University, Hangzhou, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Wang
authors.affiliation: Cleveland Clinic Epilepsy Center.
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Gonzalez-Martinez
authors.affiliation: Cleveland Clinic Epilepsy Center.
authors.forename: W
authors.initials: W
authors.lastname: Bingaman
authors.affiliation: Cleveland Clinic Epilepsy Center.
authors.forename: Andreas V
authors.initials: AV
authors.lastname: Alexopoulos
mesh_terms: D000293:Adolescent; D000328:Adult; D001426:Bacterial Proteins; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D002648:Child; D004569:Electroencephalography; D017034:Epilepsy, Frontal Lobe / Q000473:pathology* / Q000503:physiopathology; D005098:Exotoxins; D005260:Female; D059907:Functional Neuroimaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging / Q000379:methods; D049268:Positron-Emission Tomography; D055815:Young Adult
chemical_list: D001426:Bacterial Proteins; D005098:Exotoxins; C027951:erythrogenic toxin
keywords: Epilepsy; Focal cortical dysplasia; MRI; MRI postprocessing; MRI-negative epilepsy; Orbitofrontal epilepsy; Presurgical evaluation; Voxel-based morphometry