title: Seizure focus affects regional language networks assessed by fMRI.
abstract: OBJECTIVE
  To investigate the degree of language dominance in patients with left and right hemisphere seizure foci compared to normal volunteers using a fMRI reading comprehension task.
  
  
  METHODS
  Fifty patients with complex partial epilepsy, aged 8 to 56 years and 33 normal volunteers, aged 7 to 34 had fMRI (1.5 T) and neuropsychological testing. Participants silently named an object described by a sentence compared to a visual control. Data were analyzed with region of interest (ROI) analysis based on t maps for inferior frontal gyrus (IFG), midfrontal gyrus (MFG), and Wernicke area (WA). Regional asymmetry indices (AIs) were calculated [(L - R)/(L + R)]; AI > 0.20 was deemed left dominant and AI < 0.20 as atypical language.
  
  
  RESULTS
  Left hemisphere focus patients had a higher likelihood of atypical language than right hemisphere focus patients (21% vs 0%, chi2 < 0.002). Left hemisphere focus patients, excluding those with atypical language, had lower regional AI in IFG, MFG, and WA than controls. Right hemisphere focus patients were all left language dominant and had a lower AI than controls in WA and MFG, but not for IFG. AI in MFG and WA were similar between left hemisphere focus/left language patients and right hemisphere focus patients. Patients activated more voxels than healthy volunteers. Lower AIs were attributable to greater activation in right homologous regions. Less activation in the right-side WA correlated with better verbal memory performance in right focus/left hemisphere-dominant patients, whereas less strongly lateralized activation in IFG correlated better with Verbal IQ in left focus/left hemisphere-dominant patients.
  
  
  CONCLUSIONS
  Patients had lower asymmetry indices than healthy controls, reflecting increased recruitment of homologous right hemisphere areas for language processing. Greater right hemisphere activation may reflect greater cognitive effort in patient populations, the effect of epilepsy, or its treatment. Regional activation patterns reflect adaptive efforts at recruiting more widespread language processing networks that are differentially affected based on hemisphere of seizure focus.
authors.affiliation: Department of Neurosciences, Children's National Medical Center, George Washington University School of Medicine, Washington, DC, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Berl
authors.forename: L M
authors.initials: LM
authors.lastname: Balsamo
authors.forename: B
authors.initials: B
authors.lastname: Xu
authors.forename: E N
authors.initials: EN
authors.lastname: Moore
authors.forename: S L
authors.initials: SL
authors.lastname: Weinstein
authors.forename: J A
authors.initials: JA
authors.lastname: Conry
authors.forename: P L
authors.initials: PL
authors.lastname: Pearl
authors.forename: B C
authors.initials: BC
authors.lastname: Sachs
authors.forename: C B
authors.initials: CB
authors.lastname: Grandin
authors.forename: C
authors.initials: C
authors.lastname: Frattali
authors.forename: F J
authors.initials: FJ
authors.lastname: Ritter
authors.forename: S
authors.initials: S
authors.lastname: Sato
authors.forename: W H
authors.initials: WH
authors.lastname: Theodore
authors.forename: W D
authors.initials: WD
authors.lastname: Gaillard
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D004827:Epilepsy / Q000150:complications* / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007802:Language; D007806:Language Disorders / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology*; D007807:Language Tests; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology; D009473:Neuronal Plasticity / Q000502:physiology; D011237:Predictive Value of Tests; D014705:Verbal Behavior / Q000502:physiology