Neuropathology of delayed encephalopathy in cats induced by heavy-ion irradiation.
OBJECTIVE
The pathogenesis of delayed encephalopathy induced by heavy-ion irradiation was investigated experimentally in cats. The left cerebral hemispheres were irradiated with 15-40 Gy of heavy ions (carbon), and histologically and morphometrically examined 12 months later.


RESULTS
In the irradiated cerebral white matter the following occurred as the dose increased: astrocytic swelling, then the dilatation of small blood vessels with a fibrous thickening of the wall, and then loosening of the white matter with cavity formation and diffuse albumin deposition. Pathological features of these cavities suggested that they are induced by long-standing edema. Although the dilated vessels were arteries, veins, and capillaries, arteriovenous shunt and damage of the smooth muscle cells of the arterial media were absent. Changes of the cerebral cortex were scarce. Morphometrically, the irradiated cerebral white matter was swollen, and the capillary density tended to be reduced in the deep cortex and subcortical white matter, but this effect was not dose dependent.


CONCLUSIONS
Heavy-ion irradiation induces delayed encephalopathy in cats, preferentially involving the white matter. The cardinal pathogenesis was long-standing edema of the white matter due to vascular hyperpermeability, and the vascular dilatation seemed to be caused by a reduction in the vascular bed and/or hemoconcentration due to hyperpermeability.
Okeda
Riki
R
Department of Neuropathology, Medical Research Institute, Tokyo Medical & Dental University, Tokyo, Japan.
Okada
Shinobu
S
Kawano
Akihiro
A
Matsushita
Satoru
S
Kuroiwa
Toshihiko
T
D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000473:pathology / Q000528:radiation effects*; D001927:Brain Diseases / Q000209:etiology*; D002196:Capillaries / Q000473:pathology; D002415:Cats; D002540:Cerebral Cortex / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D020450:Heavy Ions; D007477:Ions; D008297:Male; D051381:Rats; D013997:Time Factors; D014965:X-Rays
D007477:Ions