title: Identification of abnormal neuronal metabolism outside the seizure focus in temporal lobe epilepsy.
abstract: OBJECTIVE
  The aim of this study was to identify metabolically abnormal extrahippocampal brain regions in patients with temporal lobe epilepsy with (TLE-MTS) and without (TLE-no) magnetic resonance imaging (MRI) evidence for mesial-temporal sclerosis (MTS) and to assess their value for focus lateralization by using multislice 1H magnetic resonance spectroscopic imaging (MRSI).
  
  
  METHODS
  MRSI in combination with tissue segmentation was performed on 14 TLE-MTS and seven TLE-no and 12 age-matched controls. In controls, N-acetylaspartate/(creatine + choline) [NAA/(Cr+Cho)] of all voxels of a given lobe was expressed as a function of white matter content to determine the 95% prediction interval for any additional voxel of a given tissue composition. Voxels with NAA/(Cr+Cho) below the lower limit of the 95% prediction interval were defined as "pathological" in patients and controls. Z-scores were used to identify regions with a higher percentage of pathological voxels than those in controls.
  
  
  RESULTS
  Reduced NAA/(Cr+Cho) was found in ipsilateral temporal and parietal lobes and bilaterally in insula and frontal lobes. Temporal abnormalities identified the epileptogenic focus in 70% in TLE-MTS and 83% of TLE-no. Extratemporal abnormalities identified the epileptogenic focus in 78% of TLE-MTS but in only 17% of TLE-no.
  
  
  CONCLUSIONS
  TLE is associated with extrahippocampal reductions of NAA/(Cr+Cho) in several lobes consistent with those brain areas involved in seizure spread. Temporal and extratemporal NAA/(Cr+Cho) reductions might be helpful for focus lateralization.
authors.affiliation: Department of Veterans Affairs Medical Center, Magnetic Resonance Spectroscopy Unit, California Pacific Medical Center, Pacific Epilespy Program, University of California, San Francisco, 94115, USA.
authors.forename: Suzanne G
authors.initials: SG
authors.lastname: Mueller
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Laxer
authors.forename: Nathan
authors.initials: N
authors.lastname: Cashdollar
authors.forename: Derek L
authors.initials: DL
authors.lastname: Flenniken
authors.forename: Gerald B
authors.initials: GB
authors.lastname: Matson
authors.forename: Michael W
authors.initials: MW
authors.lastname: Weiner
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000378:metabolism / Q000473:pathology; D004833:Epilepsy, Temporal Lobe / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000378:metabolism* / Q000473:pathology*; D012640:Seizures / Q000378:metabolism / Q000473:pathology; D018709:Statistics, Nonparametric