186 ORVILLE T. BAILEY 



Summary 



A review of the literature related to the effects of gamma and roentgen 

 radiation of the central nervous system is presented and compared with 

 personal material, with a few comments on the effects of beta radiation. 



The reaction of the central nervous system hours or a few days after radia- 

 tion is an acute inflammatory one. dominated by \asculitis, meningitis, and 

 choroid plexitis. Regressive changes, apparently mostly reversible, are present 

 in the granide cells of the cerebellum. 



Young animals are more susceptible to radiation damage than adults, but 

 histologic effects can be produced at any age with sufficient dosage. 



Different and more extensive degenerative processes become evident as the 

 time interval between radiation and sacrifice is lengthened. This interval can 

 be reduced by increasing the dose of radiation, increasing the intensity of 

 radiation, and possibly by other factors. 



In late stage of radiation reaction, there is extensive damage to neurons, 

 with selectixity for the white matter and particidar sensitivity of the brain 

 stem and hypothalamus. Degeneratixe changes in blood vessels, sometimes 

 with complete occlusion, can be demonstrated at this stage. 



The effects on neurons are considered by most, but not all, workers to be 

 direct effects and not mediated through \ascular insufficiency. 



All types of glia show degenerative changes after radiation, and there is a 

 prolonged inhibition of glial response in repair. Proliferation of collagenous 

 tissue is important in the first stages of repair. C'ompound granular corpuscle 

 formation is resumed before astrocytic proliferation begins. Some months 

 after radiation, astrocytosis becomes exuberant. 



Despite many contradictions in results and interpretation, a basic pattern 

 of degeneration and repair in response to gamma and roentgen radiation is 

 becoming apparent by light microscopy. The most striking single featme is 

 the progressive increase in evidence of damage as time after radiation is 

 lengthened. It is impossible to predict end results from any characteristics of 

 the acute response. Investigations by all techniques will be recjuired to 

 explain the processes going on in the interval, and studies of this type may- 

 well have biologic implications beyond the field of radiation pathology. 



References 



.\lquRr and Faure-Beaulicu, M. 1909. L'action du radium sur les tissus du nevraxe. 



Nouv. iconog.Salpet.22, 109-113. 

 Alvord E. C, and Brace, K. C. 1957. X-ray induced pyknosis of cerebellar granule 



cells in guinea pigs and its suppression by barbiturate anesthesia. /. Neuropathol. 



Exptl. Neurol. 16, 3-17. 



