Subcortical U-fibers layer preservation in brain edema.

The mechanism involved in the relative preservation of the subcortical U-fibers in the arcuate zone was studied in a post infarct edema after sagittal superior sinus occlusion. Superior sagittal sinus (SSS) of 36 mongrel cats were occluded by polymer injection. Immediately before the occlusion Evans-blue (EB) was administered intravenously. The cats were killed 1, 2, 3, 6, 12, 24, 72 and 120 hours after sinus occlusion. In 20 cats in which cortical veins were occluded, in addition to the SSS, EB was extravasated. In 9 of these cats, which had moderate edema, EB-staining was present only in the cortex. In 11 cats with severe edema, massive EB extravasation was observed also in the white matter. The U-fiber layer was free of EB, suggesting that the extension of edema was blocked by this zone. Our findings demonstrated that the U-fibers act not only as a resistance against extension of edema from white to gray matter, but also in a reverse direction. The characteristics of the spread of brain edema is not yet completely understood; both anatomical and biochemical peculiarities from its basis. Different morphological patterns in the astrocytic reaction as well as the U-fibers sector vascularization are important. To evaluate the role of each one of these factors in the preservation of subcortical U-fiber layer in brain edema further investigations should be done.