title: Responses of the Human Brain to Mild Dehydration and Rehydration Explored In Vivo by 1H-MR Imaging and Spectroscopy.
abstract: OBJECTIVE
  As yet, there are no in vivo data on tissue water changes and associated morphometric changes involved in the osmo-adaptation of normal brains. Our aim was to evaluate osmoadaptive responses of the healthy human brain to osmotic challenges of de- and rehydration by serial measurements of brain volume, tissue fluid, and metabolites.
  
  
  METHODS
  Serial T1-weighted and (1)H-MR spectroscopy data were acquired in 15 healthy individuals at normohydration, on 12 hours of dehydration, and during 1 hour of oral rehydration. Osmotic challenges were monitored by serum measures, including osmolality and hematocrit. MR imaging data were analyzed by using FreeSurfer and LCModel.
  
  
  RESULTS
  On dehydration, serum osmolality increased by 0.67% and brain tissue fluid decreased by 1.63%, on average. MR imaging morphometry demonstrated corresponding decreases of cortical thickness and volumes of the whole brain, cortex, white matter, and hypothalamus/thalamus. These changes reversed during rehydration. Continuous fluid ingestion of 1 L of water for 1 hour within the scanner lowered serum osmolality by 0.96% and increased brain tissue fluid by 0.43%, on average. Concomitantly, cortical thickness and volumes of the whole brain, cortex, white matter, and hypothalamus/thalamus increased. Changes in brain tissue fluid were related to volume changes of the whole brain, the white matter, and hypothalamus/thalamus. Only volume changes of the hypothalamus/thalamus significantly correlated with serum osmolality.
  
  
  CONCLUSIONS
  This is the first study simultaneously evaluating changes in brain tissue fluid, metabolites, volume, and cortical thickness. Our results reflect cellular volume regulatory mechanisms at a macroscopic level and emphasize that it is essential to control for hydration levels in studies on brain morphometry and metabolism in order to avoid confounding the findings.
authors.affiliation: From the Department of Neuroradiology (A.B., M.B., A.J.B.), University of Heidelberg, Heidelberg, Germany armin.biller@med.uni-heidelberg.de.
authors.forename: A
authors.initials: A
authors.lastname: Biller
authors.affiliation: Department of Radiology (M.R.), Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts Martinos Center for Biomedical Imaging (M.R.), Charlestown, Massachusetts Massachusetts Institute of Technology Computer Science and AI Lab (M.R.), Cambridge, Massachusetts.
authors.forename: M
authors.initials: M
authors.lastname: Reuter
authors.affiliation: Department of Psychiatry and Behavioral Sciences (B.P.), Stanford University, Stanford, California Department of Clinical Neurology (B.P., A.J.B.), FMRIB Centre, University of Oxford, Oxford, UK.
authors.forename: B
authors.initials: B
authors.lastname: Patenaude
authors.affiliation: Department of Neuroradiology (G.A.H., A.J.B.), University of Würzburg, Würzburg, Germany.
authors.forename: G A
authors.initials: GA
authors.lastname: Homola
authors.affiliation: Research Center for Magnetic-Resonance-Bavaria (F.B.), Würzburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Breuer
authors.affiliation: From the Department of Neuroradiology (A.B., M.B., A.J.B.), University of Heidelberg, Heidelberg, Germany.
authors.forename: M
authors.identifier: http://orcid.org/0000-0002-9094-6769
authors.initials: M
authors.lastname: Bendszus
authors.affiliation: From the Department of Neuroradiology (A.B., M.B., A.J.B.), University of Heidelberg, Heidelberg, Germany Department of Clinical Neurology (B.P., A.J.B.), FMRIB Centre, University of Oxford, Oxford, UK Department of Neuroradiology (G.A.H., A.J.B.), University of Würzburg, Würzburg, Germany.
authors.forename: A J
authors.initials: AJ
authors.lastname: Bartsch
mesh_terms: D001826:Body Fluids / Q000378:metabolism; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D003681:Dehydration / Q000378:metabolism / Q000473:pathology*; D005440:Fluid Therapy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D066244:Proton Magnetic Resonance Spectroscopy; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water