Demyelinization Induced in the Brains of Monkeys by Means of Fast Neutrons

Abstract

Demyelinization was regularly conspicuous in the white matter of the rostral portions of the brains of 6 monkeys sacrificed 14 to 22 months after exposure of the ocular regions to 850 r.e.p. of 14 mev. neutron radiation and it was not present in the brain of a monkey 2 months after radiation under identical conditions; or in those of 5 non-radiated animals serving as controls. In early lesions, the individual myelin sheaths were varicose and fragmented, while the neurons, axons, and glial cells remained normal in appearance. With the passage of time, the degeneration of myelin became more marked and in later stages was accompanied by a degeneration of the axis cylinders, a proliferation of astrocytes and microglia, and minor cytological changes in the oligodendroglia, the whole process occurring essentially without inflammation or notable changes in the cerebral or meningeal blood vessels. The findings show that neutron radiation has the property of destroying myelin in the living animal and inducing changes that are notably similar in their pathogenesis to those that characterize disseminated encephalomyelitis in human beings.

Delayed Vascular Injury after Single High-Dose Irradiation in the Rat Brain: Histologic, Immunohistochemical, and Angiographic Studies

“…All animals irradiated with 100 Gy showed cystic necrosis in the treated hemisphere after 9 months. Necrotic areas appeared exclusively in the white matter of the brain, which is known to be preferentially sensitive to radiation (41,42). Radiation necrosis was surrounded by areas of enlargement of the endothelial cells, blood vessel dilatation, thickening of the blood vessel wall, and hypertrophy of adjacent astrocytes.…”

Cerebral necrosis following neutron radiation of an extracranial tumor

“…These observations suggest that special attention should be given to treatment field design when neutrons are used, especially in view of the recent interest in neutron therapy for non-epidermoid tumors of the head and neck [1]. Several studies have emphasized some histological peculiarities of neutroninduced brain damage, including extreme diffusion of the lesions [9], preferential myelin destruction [10] and massive proliferation of fibrillary astrocytes [9,11]. However, the lesion observed in our patient did not differ from the classic form of delayed radiation necrosis.…”