[Subacute brain atrophy induced by radiation therapy of malignant brain tumors].

In order to analyze brain atrophy after radiation therapy to the brain tumors, we calculated a CSF-cranial volume ratio on CT scan as an index of brain atrophy, and estimated dementia-score by Hasegawa's method in 91 post-irradiated patients with malignant brain tumors. Radiation-induced brain atrophy was observed in 51 out of 91 patients (56%) and dementia in 23 out of 47 patients (49%). These two conditions were closely related, and observed significantly more often in aged and whole-brain-irradiated patients. As radiation-induced brain atrophy accompanied by dementia appeared 2-3 months after the completion of radiation therapy, it should be regarded as a subacute brain injury caused by radiation therapy.