CT Findings in Brain Edema

Abstract

Cranial CT is the first clinical examination allowing direct visualization of brain edema, because different absorption of X-rays in soft tissues can be distinguished with high resolution. The X-ray absorption depends on the concentration of elements with high atomic weight. Consequently, the brain water content should affect the tissue density, making brain edema visible because the concentration of X-ray absorbing elements can be expected to decline in this condition. Are as of lower density than normal tissue appear to reflect brain edema in the CT. Thus, the extent of brain edema can be exactly determined by cranial CT. Due to the varying extents of brain edema we suggest that the peri-focal brain edema should be graduated (KAZNER et al. , 1975). As an edema of degree I we qualify a perifocal edematous margin up to an average of 2 cm (see Fig. 1). Not only tumors but also all kinds of intracerebral hematomas in their early stages are surrounded by narrow dark zones of low absorption reflecting brain edema (see Fig. 2). During the course of time the low-absorption are a widens, which does not indicate an extention of the edema, but there sorption of the hematoma. If half a hemisphere is encroached by a cerebral edema, this is classi-fied as an edema of degree II (see Fig. 3). More extensive edemas are classified as degree III (see Figs. 4 and 5 a and b). We classified edemas in the posteriorfossa (see Figs. 6 and 7) according to this scheme.