MORPHOLOGICAL EFFECT OF X-RAYS TO THE CNS 231 



of the x-ray dose and abbre\iation of the sur\i\al time. In fully developed 

 necroses, all cellular elements were broken down, and erythrodiapedesis 

 from more or less numerous \essels occurred not only within, but also out 

 of the necrotic zone. Initial stages demonstrated a spong\' transformation of 

 the nervous tissue with only minor changes of the cellular constituents, such 

 as plasma and nuclear shrinkage. Here, erythrodiapedesis was still lacking. 

 A disorder of the hematoencephalic barrier in this initially spongy territory 

 could not be demonstrated by intra\ital trypan blue staining, while a blue 

 coloration of a large area including the surrounding region of spongy loosen- 

 ing became visible before a distinct disintegration of tissue, indicated by signs 

 of cell necrosis, were demonstrable. Solitary small diapedetic hemorrhages 

 and the immigration of single leucocytes seem to indicate a degree of perme- 

 ability disorder sufficient to allow an intraxital staining with trypan blue. 

 This beha\ior and the appearance of more or less small hemorrhages at the 

 borders of. and sometimes far from, the necrotic foci point to the significance 

 of an early disorder of the blood-brain barrier. Since ner\e cells have been 

 shown to be rather resistant within zones of edematous loosening of tissue, 

 and astrocytes even may become progressi\e, the whole process of necrosis 

 cannot be considered as solely secondary to the permeability disorder. From 

 the morphologic tacts, it seems justified to admit that in acute radionecrosis 

 from large x-ray doses ot hiizh intensity a direct effect on the nervous and 

 astrocytic tissue constituents may occur simultaneously with \ascular damage. 

 Processes of transformation, resorption, and organization de\elop slowlv and 

 are established regularly onlv at the borders of the necrotic zones. 



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