Recurrent cystic radiation necrosis of the brain.

Cystic radiation necrosis is a rare complication of radiotherapy for nasopharyngeal carcinoma. The magnetic resonance imaging (MRI) characteristics have not been described. Serial MRI images were done on a patient who developed multiple cysts in the brain as a result of irradiation for his nasopharyngeal carcinoma. The characteristic MRI features included a slightly higher T1-weighted signal than cerebrospinal fluid, surrounding white matter edema as indicated by the high T2-weighted signal, and absence of gadolinium enhancement on the cyst wall. The adjacent gray matter in the anterior temporal lobes and inferior frontal lobes, which were included in the radiation field, had gadolinium enhancement. Dosimetry data and isodose contour maps revealed that his frontal lobes and anterior temporal lobes received 7920 cGy and 5040-6480 cGy of radiation respectively. Despite placement of multiple cysto-peritoneal shunts for decompression, new cysts eventually developed and previously shunted cysts enlarged in size. The management of cystic radiation necrosis of the brain remains unsatisfactory.