FIG 1.

Supratentorial brain/skull ratios. A: Representation of the supratentorial axial ratio, defined as the axial cross-sectional brain area (lavender) measured at closest approximation of the thalamus, divided by the axial interior skull area, measured on the same slice (blue). B: Representation of the supratentorial coronal ratio, defined as the coronal cross-sectional brain area (lavender) measured at the anterior margin of the third ventricle, on the slice with the most complete view of the basilar artery, divided by the coronal interior skull area on the same slice (blue). The overall supratentorial brain/skull ratio is equal to the mean of the axial and coronal ratios. These images are visual representations created using Microsoft drawing tools, designed to illustrate how quantification was performed. Actual quantification was performed with semiautomated imaging analysis software.