title: Does brain swelling increase estimated specific gravity?
abstract: OBJECTIVE
  At the acute phase of traumatic brain injury (TBI), brain swelling contributes substantially to the development of secondary neurological lesions. Elucidating the pathophysiology of brain swelling is crucial to improve TBI management. In a previous study, specific gravity (SG) of the noncontused hemisphere, as estimated by computed tomography (CT), was higher in patients with high Marshall CT scores and severe brain swelling. The aim of this study was to investigate the relationship between estimated specific gravity (eSG) and clinical variable suggestive of brain swelling.
  
  
  METHODS
  Retrospective study of data from a prospectively established database.
  
  
  METHODS
  Neurology ICU in a teaching hospital in Paris, France.
  
  
  METHODS
  We studied 20 patients with severe traumatic brain injury (TBI), 20 patients with high-grade subarachnoid hemorrhage (SAH) presenting similar brain-swelling criteria, 20 patients with low-grade SAH, and 20 healthy controls.
  
  
  METHODS
  None.
  
  
  RESULTS
  Estimated brain specific gravity was acquired from CT images obtained at ICU admission. eSG was estimated in the overall intracerebral content and in a region-of-interest composed of white matter and the diencephalon. eSG in the region of interest was significantly higher in the TBI patients than in the high-grade SAH patients (1.0350 +/- 0.0041 vs. 1.0310 +/- 0.0019 g/ml, P < 0.05). eSG was similar in the high-grade SAH, low-grade SAH, and control groups.
  
  
  CONCLUSIONS
  Our findings do not support a causal link between brain swelling and eSG elevation. The eSG increase in severe TBI patients is not due to brain swelling.
authors.affiliation: Department of Anesthesiology and Critical Care, Pitié-Salpêtrière Teaching Hospital, Assistance Publique-Hôpitaux de Paris, Pierre and Marie Curie Paris 6 University, Paris, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Degos
authors.forename: Ana-Rosa
authors.initials: AR
authors.lastname: Pereira
authors.forename: Thomas
authors.initials: T
authors.lastname: Lescot
authors.forename: Paola
authors.initials: P
authors.lastname: Sanchez-Peña
authors.forename: Mounir
authors.initials: M
authors.lastname: Daoudi
authors.forename: Abderrezak
authors.initials: A
authors.lastname: Zouaoui
authors.forename: Pierre
authors.initials: P
authors.lastname: Coriat
authors.forename: Louis
authors.initials: L
authors.lastname: Puybasset
mesh_terms: D000328:Adult; D000368:Aged; D001929:Brain Edema / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013046:Specific Gravity; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult