Experimental cerebral edema

ALTHOUGH THE EXISTENCE, pathologic findings, and clinical classification of cerebral edema had been described long before the beginning of this century, the concept and classification were summarized and clarified by Anton1 in 1904. In his book, he described cerebral edema as a general or localized swelling of brain substance which shows increased accumulation of serous fluid in the perivascular space and tissue space. In contrast, the concept of brain swelling was introduced in 1905 by Reichardt,2 who described it as an increase of brain volume and weight with firm, dry brain substance. In 1929, Spatzl tried to differentiate cerebral edema from brain swelling. According to his definition, brain swelling consisted of a dry brain with increased consistency and flattened gyri. and cerebral edema repres2nted an increase of free tissue fluid in the brain. The former was frequently observed in the brain tissue surrounding brain tumors. This subject was extensively discussed in the 1940s. Although Scheinker4 observed histologic differences between cerebral edema and cerebral swelling, Greenfield5 and Perret and Kernohane thought that swelling was chronic and mild and that edema was an acute and severe stage of the same process. Recently, Ziilch7 expressed the opinion that they were different pathologically and morphologically. Biochemical aspects of cerebral edema were investigated by Alexander and Looneys and by Stewart-Wallace.9 The latter demonstrated an increase of fluid, sodium, and chloride in edematous white matter adjacent to brain tumors and suggested that these changes represented serum infiltrate in the extracellular space. Later, an increase of water-soluble protein in edematous tissue was It had been well accepted from light-microscopic or physiochemical investigation that an increase of extracellular space accounted for the increase in the volume of edematous cerebral tissue, but electron microscopy demonstrated a virtual absence of extracellular space in normal cerebral tissuel"J4 and in edematous cerebral cortex.15-1T However, more recent studies with the electron microscope have shown an increased extracellular space18.19 in edematous white matter. The existence of extracellular space in cerebral tissue was reconfirmed physiologically, particularly with the use of radioisotopes.20-22 On the other hand, alterations in the cellular components of edematous cerebral tissue have been investigated primarily by means of the light microscope. Anton1 initially mentioned changes in neuroglia, and Spat23 demonstrated swelling of astrocytes (with the Cajal gold stain) in the white matter near a brain tumor. Penfield and Cone2s described acute swelling of oligodendroglia in inflammatory disease or around an abscess but did not find marked change in oligodendrocytes in experimental cerebral edema, With regard to the cerebral edema around a brain tumor, Greenfield5 found more astrocytic reaction than changes in oligodendrocytes, but Perret and Kernohane and Reid24 described more prominent changes in oligodendrocytes.