A Demyelinating or Malacic Myelopathy 



and Myodegeneration— 



Delayed Effect of Localized X-irradiation 



In Experimental Rats and Monkeys 



J. R. M. Innes and a. Carsten 



Brookhaven National Laboratory 

 Upton, Long Island, New York 



Introduction 



For many years the central nervous system was considered hislily resistant 

 to radiation damaiie — and statements to this effect occasionally still appear. 

 It is manifest that there must be some ciualification by reference to the part 

 of the system exposed, the conditions and dosimetry of irradiation, and the 

 species and age of the animals used. The earlier experimental irradiation 

 work on the normal nervous system was reviewed by Warren (1943) and 

 Hicks f 1952 1. We are concerned here with oiu initial experimental irradi- 

 ation studies on the spinal cord of rats and with some observations on 

 experimental monkeys. 



In man the hazard attached to x-irradiation ot the brain or spinal cord, 

 whether by deliberate design for radiotherapy or unaxoidably when extra- 

 neural sites must be exposed, is well established. Late or delayed irradiation 

 effects on the nerxous system are different from acute massixe radionecrosis 

 which follows extremely high doses. The problems associated with the two 

 types of damage are multiple and complex, and the literature was reviewed 

 by Zeman ( 1955) and by Zollinger 1960) . Many original papers on human 

 cases have been perused, e.g., Lyman ct al. (1933), Stevenson and Eckhart 

 (1945), Pennybacker and Russell (1948). Greenfield and Stark (1948), 

 Boden (1948), Friedman i 1954 1, Itabashi et al. (1957), and Dynes and 

 Smedal ( I960). It is not necessary to deal with these contributions individ- 

 uallv. but we can reiterate the patholologic problems to be faced. The 

 number of reported cases in the literature is an inde.x neither to the inci- 

 dence of delayed irradiation lesions in the spinal cord, nor to the importance 

 of the hazard, as is evident from discussions with neurologists, neuropathol- 



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