Radiation-Induced Multiphasic Demyelination

Radiation-induced brain injury encompasses a wide range of neurotoxic effects varying in severity and ranging from transient edema to progressive white-matter necrosis. Classification is based on the timing of onset of symptoms after radiotherapy: 1) acute injury that occurs within days to weeks, 2) early delayed injury develops within weeks to months, and 3) late delayed injury that manifests after 6 months or longer (1). One of the proposed mechanisms of the early delayed injury is acute demyelination, which has been reported in 6 patients without history of demyelinating disease. In these cases, demyelination developed within 1-4 months after radiotherapy (2-5). We describe a case of demyelination in a patient following a course of radiotherapy targeted at the residuum of a pituitary macroadenoma.