[Post-radiotherapy brain lesions]

Abstract

Recurrent symptoms or signs during or after therapeutic brain irradiation may be due to the progression of the irradiated tumour, necrosis of normal brain tissue, necrosis of tumour, or all three of these. We have studied 12 patients with pathologically proven radiation-induced damage of normal brain tissue. All patients were exposed to a therapeutic range of radiation for an intra or extracranial tumour. Seven patients were exposed to 280 to 300 rads per day, three times weekly to a total dose of 4500 to 6000 rads (fractionated). Five patients received 750 to 850 rads per day, on days 1, 3, 21 and 23 (split-course). The diagnosis of radiation-induced brain lesions is difficult. CT scan is the most informative diagnostic procedure. The various patterns of radiation-induced brain lesions on CT are nonspecific. However where there is sufficient clinical data suggesting radiation-induced brain lesions, and a good correlation between CT abnormalities and the maximum delivered dose, on dose distribution maps of the brain exposed to a high cumulative radiation dose, the diagnosis may be accepted. The time interval between the end of radiation therapy and the occurrence of radiation-induced lesions was shorter in the patient group exposed to a split-course therapy (median time: 9.6 months) as opposed to the patient group exposed to a fractionated radiation (median time: 45 months). Pathologically the lesions corresponded to either a demyelinated area within the white matter with minimal vasculopathy or an area of coagulation necrosis with varying degrees of necrosis, delamination or hyalinosis of small blood vessels.(ABSTRACT TRUNCATED AT 250 WORDS)