ACUTE CNS SYNDROME OF BURROS 505 



Disturbance of consciousness was manifested throughout the central 

 nervous system syndrome. An initial period of depression was followed by 

 irritability, delirium, and mania. Irritability was manifested by excitement, 

 biting, and kicking in response to minor provocation and general resentment 

 of any external stimuli; delirium, by aimless wandering and continuous 

 tail switching, as if molested by flies: and mania, by violent and purposeless 

 movements. If an animal progressed to a state of mania. e\entually coma 

 and death ensued. 



There was also pronounced motor irritation, characterized by clonic 

 spasms (trembling, muscle tremors, and bobbing of head) and forced move- 

 ments [circling, pressing forward (Fig. IB), and grinding of teeth or 

 chewing motion], usually with excessive salivation. 



Derangement of sensation was indicated by hyperesthesia and distiubance 

 of sight and equilibrium. 



Paralysis of lower lip and tongue was common. Incoordination, although 

 somewhat difficult to recognize in the presence of distmbed equilibrium, 

 was definitely observed in many animals. 



Other observations were lacrimation in all animals, swelling of the neck 

 in some, and anorexia, which began with the onset of depression. 



The onset and duration of neurologic symptoms varied with dose and 

 dose rate. In the Nevada group, 19 deaths occurred within 24 hours. The 

 first death (625 rep) occurred 5 hours after exposure. In the head-irradiated 

 burros the first death i 1,200 r) occurred at 15 hours; in the Godiva burros, 

 at 71 hours after exposure. The severity of neurologic manifestation in re- 

 spect to dose appeared to \ary with the individual. Some animals in the 

 low dose groups exhibited violent response, even though there was a pro- 

 longed postirradiation period of apparently normal beha\ior. 



P.\THOLOGV 



The most frecjuent yross lesion in the head-irradiated burros was diffuse 

 hemorrhage into the subarachnoid space on the posterior dorsal and/or 

 ventral aspect of the medulla and cerebellum (Fig. 2). Occasionally the 

 meninges were congested and contained small hemorrhages. A similar pat- 

 tern of lesions was noted in the Godi\a burros. The Ne\acla burros exhibited 

 few gross lesions. 



Perivascular cuffing (Fig. 3) was the most frequent lesion seen in all 

 three groups. It was characterized by clusters of neutrophils around the 

 parenchymal and pial vessels, as well as moderate to pronounced infiltration 

 at other sites (Fig. 4). In the head-irradiated animals, these clusters con- 

 tained many eosinophils. 



Hemorrhages were seen frequently in all groups, primarily around the 



