212 W. SCHOLZ, W. SCHLOTE AND W. HIRSCHBERGER 



Accordinoly, since 1956, we have studied the neuropathology of x-ray 

 lesions produced by irradiation of the spinal cord of rabbits.^ A 3 x 6 cm 

 field on the back, corresponding to the upper thoracic segments of the cord, 

 was irradiated. The technical conditions were: 180-200 kv, 18 mA, 0.95- 

 1.12. Cu half value layer, filter 0.5 Cu. 60 r per min, focus — skin distance 

 50 cm, and pendulum angle 70° on both sides. The average dose was 250 r 

 daily; total doses were 3,000 to 1 1,000 r given over 12 to 40 days. All animals 

 acquired paralysis of the hind legs and loss of sphincter function within 4 to 

 33 weeks after the beginning of irradiation. This investigation was published 

 in Psychiatria ct Nciirologia Japonica, 1959, and only the important features 

 will be mentioned here. The white matter of the spinal cord was much 

 more affected than the gray substance and showed more or less circum- 

 scribed areas of disintegration following the radial distribution of the spinal 

 vessels entering from the vasocorona along the whole periphery of the cord. 

 Regressive changes of the small vessels with slight perivascular astrocytic 

 reaction within the focal lesions suggest the transudation of a fluid histo- 

 logically not demonstrable, causing swelling and disintegration of the myelin 

 fibers. Only in a few cases did the gray substance participate in the changes. 

 Here, plasmatic extravasation, partly with erythrodiapedesis, could be ob- 

 served, followed by an astrocytic reaction and some regressive changes in 

 some nerve cells. Although a reaction of the neuroglia was observed, it 

 remained rather scanty, especially in the white matter. Regardless of the 

 fact that some lesions were 3 to 4 weeks old, sudanophilic material was not 

 observed. In both white and gray matter, plasmatic disintegration of the 

 walls of larger vessels was encoimtered occasionally, but plasmatic exudation 

 was seen only in the gray substance. Thus the morphologic feature patho- 

 genetically pointed to the primacy of processes of transudation, exudation, 

 and erythrodiapedesis, that is, to a breakdown of the barrier function of the 

 spinal vessels. This concept was further supported by intravital injection of 

 tiypan blue (Fig. 1). There are blue stained foci in the white matter 



Fig. 1. Delayed lesion of the spinal cord of a rabbit after fractionated x-irradiation, 

 intravitally stained with trypan blue. Beneath some foci of disintegration in the white 

 matter, the whole gray substance although demonstrating no disintegration, has taken 

 the blue color. 



' We received the material from the radiologist Dr. Breit, who was interested in 

 questions of tolerance dose, dose fractioning, and concentric application by a pendulum 

 x-ray machine. 



