title: Proton MR spectroscopy and MRI-volumetry in mild traumatic brain injury.
abstract: OBJECTIVE
  More than 85% of brain traumas are classified as "mild"; MR imaging findings are minimal if any and do not correspond to clinical symptoms. Our goal, therefore, was to quantify the global decline of the neuronal marker N-acetylaspartate (NAA), as well as gray (GM) and white matter (WM) atrophy after mild traumatic brain injury (mTBI).
  
  
  METHODS
  Twenty patients (11 male, 9 female; age range, 19-57 years; median, 35 years) with mTBI (Glasgow Coma Scale score 13-15 with loss of consciousness for at least 30 seconds) and 19 age- and sex-matched control subjects were studied. Seven patients were studied within 9 days of TBI; the other 13 ranged from 1.2 months to 31.5 years (average and median of 4.6 and 1.7 years, respectively) after injury. Whole-brain NAA (WBNAA) concentration was obtained in all subjects with nonlocalizing proton MR spectroscopy. Brain volume and GM and WM fractions were segmented from T1-weighted MR imaging and normalized to the total intracranial volume, suitable for intersubject comparisons. The data were analyzed with least squares regression.
  
  
  RESULTS
  Patients with mTBI exhibited, on average, a 12% WBNAA deficit that increased with age, compared with the control subjects (p<.05). Adjusted for age effects, patients also suffered both global atrophy (-1.09%/year; P=.029) and GM atrophy (-0.89%/year; P=.042). Patients with and without visible MR imaging pathology, typically punctate foci of suspected shearing injury, were indistinguishable in both atrophy and WBNAA.
  
  
  CONCLUSIONS
  WBNAA detected neuronal/axonal injury beyond the minimal focal MR-visible lesions in mTBI. Combined with GM atrophy, the findings may provide further, noninvasive insight into the nature and progression of mTBI.
authors.affiliation: Department of Radiology, New York University School of Medicine, New York, NY 10016, USA. oded.gonen@med.nyu.edu
authors.forename: B A
authors.initials: BA
authors.lastname: Cohen
authors.forename: M
authors.initials: M
authors.lastname: Inglese
authors.forename: H
authors.initials: H
authors.lastname: Rusinek
authors.forename: J S
authors.initials: JS
authors.lastname: Babb
authors.forename: R I
authors.initials: RI
authors.lastname: Grossman
authors.forename: O
authors.initials: O
authors.lastname: Gonen
mesh_terms: D000328:Adult; D000367:Age Factors; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001284:Atrophy; D001369:Axons / Q000473:pathology; D001921:Brain / Q000378:metabolism* / Q000473:pathology*; D001930:Brain Injuries / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000473:pathology; D011522:Protons
chemical_list: D011522:Protons; D001224:Aspartic Acid; C000179:N-acetylaspartate