Conclusions
Fractionation does not adequately spare normal white matter from late radiation side effects.
Purpose
To determine the late effects of fractionated versus single-dose cranial radiation on murine white matter.
Results
Weight gain was temporarily reduced after irradiation; greater loss was seen after single versus fractionated doses. Oligodendrocyte progenitor cells were reduced early and late after both single and fractionated irradiation. Both protocols also increased myelin g-ratio, reduced the number of nodes of Ranvier, and promoted a shift in the proportion of small, unmyelinated versus large, myelinated axon fibers. Conclusions: Fractionation does not adequately spare normal white matter from late radiation side effects.