Does Brain Swelling Increase Estimated Specific Gravity?
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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.
Retrospective study of data from a prospectively established database.
Neurology ICU in a teaching hospital in Paris, France.
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.
Measurements and 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.
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.
KeywordsTraumatic brain injury Specific gravity Computed tomography Subarachnoid hemorrhage Brain swelling Blood–brain barrier
This work was supported by two nonprofit organizations, the JEPU and the Fondation des Gueules Cassées. We thank the staff of the neuro-intensive care unit of the Pitié-Salpêtrière Teaching Hospital for their participation in this study and Jorge Gallego for his methodological assistance.
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