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Brain edema is routinely measured using the wet-dry method. Volume, however, is the sum total of all cerebral tissues, including water. Therefore, volumetric change following injury may not be adequately quantified using percentage of edema. We thus tested the hypothesis that dried brains can be reconstituted with water and then re-measured to determine the actual volume. Subarachnoid hemorrhage (SAH) was induced by endovascular perforation in adult male Sprague-Dawley rats (n = 30). Animals were euthanized at 24 and 72 h after evaluation of neurobehavior for determination of brain water content. Dried brains were thereafter reconstituted with equal parts of water (lost from brain edema) and centrifuged to remove air bubbles. The total volume was quantified using hydrostatic (underwater) physics principles that 1 ml water (mass) = 1 cm(3) (volume). The amount of additional water needed to reach a preset level marked on 2-ml test tubes was added to that lost from brain edema, and from the brain itself, to determine the final volume. SAH significantly increased both brain water and volume while worsening neurological function in affected rats. Volumetric measurements demonstrated significant brain swelling after SAH, in addition to the brain edema approach. This modification of the "wet-dry" method permits brain volume determination using valuable post hoc dried brain tissue.

Nos remerciements s'adressent en premier lieu à François de La Varende pour l'autorisation régulière de conduire des fouilles à la Grotte du Bison. A-m. Tillier remercie Y. Delbos et P. Rouas (Faculté d'Odontologie, Université Bordeaux 2) pour les échanges fructueux qu'ils ont eus. Le manuscrit s'est enrichi suite à une relecture attentive des experts anonymes. Enfin la qualité de l'illustration doit beaucoup à l'amicale contribution de P. Courtaud (UMR 5199-équipe A3P) et G. Devilder (UMR 5133).