Hyperbaric oxygen as prophylaxis or treatment for radiation myelitis.

This animal study was designed to investigate HBO as a treatment or prophylaxis for radiation myelitis. All animals received identical spinal cord radiation doses of 69 Gy in 10 daily fractions. Group I received no HBO; group II began HBO at the onset of signs of myelitis; group III received HBO with prophylactic intent beginning 6 wk after irradiation; and group IV received both modalities on the same day, but radiation always preceded HBO by at least 4 h. HBO consisted of 90 min oxygen at 2.4 atm abs for 20 daily treatments. Animals were objectively assessed for the loss of certain neurologic reflexes indicative of four levels of myelitis. Although all animals progressed to severe myelitis, group III animals had group-averaged levels of myelitis consistently less than control. The differences were statistically significant for several weeks. Group IV animals progressed to severe myelitis much more rapidly than any other group. Additional study is justified by this trial. Key questions to be answered include the optimal timing of HBO to produce a beneficial rather than detrimental effect.