- CT scan showing no brain injury or only a small contusion (an area of low attenuation less than 10 mm or a punctuate area of high attenuation with surrounding edema less than 5mm). CT evidence of high or mixed attenuation would be consistent with a hemorrhagic lesion and therefore not qualify to participate in the study. Evidence of skull fractures and cephalohematomas on CT would not exclude the patient from the study.