Long-term evaluation of radiation-induced brain damage by serial magnetic resonance imaging

The long-term changes during late delayed radiation-induced brain damage were investigated by serial magnetic resonance (MR) imaging of eight patients over a mean follow-up period of 45 months after irradiation. The radiation damage appeared as an enhanced lesion on T1-weighted MR images with gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) at 3 to 30 months after radiotherapy (mean 12.8 months). In all patients, an abnormal high signal intensity area on T2-weighted imaging preceded the enhanced lesion. The volume and number of enhanced lesions continued to increase for 3 to 23 months (mean 10.3 months). The high signal intensity area on T2-weighted imaging simultaneously expanded. The lesions were subsequently stabilized, and in four long-term survivors, the Gd-DTPA-enhanced lesions then decreased in size, the intervals from onset to regression were 12, 13, 17, and 35 months (mean 19.3 months), respectively. However, two patients showed a relapse of the enhanced lesion with latent periods of 8 and 9 months, respectively. Finally, the radiation-damaged brain became atrophic including the high signal intensity area on T2-weighted images. Late delayed radiation-induced brain damage continues to progress for over a year and then regresses, but thereafter a relapse may occur.