A comparison of total body and local spinal cord irradiation in experimental allergic encephalomyelitis.

Spinal cord distribution spaces of 3H-mannitol (M.W. 182) were measured to compare the effects of both total-body gamma irradiation and local (spinal cord) x-irradiation on the development of experimental allergic encephalomyelitis (EAE). Single doses of 700R, 500R, 300R, 200R and 100R total body gamma irradiation, administered 6-8 days after EAE induction, appeared to delay the onset, reduce the severity, and hasten recovery of the disease. The magnitude of this effect was approximately prportional to the administered radiation dose. A single 1000R x-irradiation dose, delivered to a 1 x 2cm area in the thoracolumbar region of the spinal cord 7 or 10 days after induction appeared to increase the severity of EAE. Mannitol distribution spaces were mildly elevated in the thoracic regions and significantly elevated in the lumbar spinal cords of cord-irradiated animals. A marked exacerbation of the disease was observed in cord-irradiated rats treated with 5000R, administered over a period of 5 days. Rats progressively lost weight during the normal course of EAE, and a simultaneous increase in wet weights of the spinal cords was seen. Slight changes in these two parameters were observed in cord-irradiated, but not in total-body irradiated animals.