Cerebral demyelination following radiotherapy

Abstract Background Subacute demyelination is a known but very rare complication of cerebral radiotherapy (RT) treatment that can occur in tissues outside the radiation field, in contrast to radionecrosis. We describe three patients with this entity and review the literature. Case report Case 1: A 30-year-old white Spanish male who received fractionated RT (54 Gy) for a second recurrence of pituitary adenoma. Four weeks after completing treatment, he developed a cerebellar syndrome. Cranial magnetic resonance imaging (MRI) revealed lesions in both cerebellar peduncles. Cerebrospinal fluid (CSF) analysis showed 20 leukocytes/mm 3 with the presence of oligoclonal bands (OCB). The patient improved with corticosteroids. Three months later, he presented with a new clinical–radiological relapse and the diagnosis of multiple sclerosis (MS) was established. Case 2: A 74-year-old white Spanish female treated with RT (15 Gy) for a left carotid-cavernous fistula. She presented with a subacute cerebellar syndrome two weeks after completing RT. Cranial MRI showed lesions in the right cerebellar peduncle and mesencephalic-pontine tectum. CSF analysis revealed 10 leukocytes/mm 3 and absence of OCB. She exhibited clinical improvement with corticosteroids. Case 3: A 46-year-old white Spanish female who received fractionated RT (54 Gy). Eight weeks after completing RT, she presented with a cerebellar syndrome and diplopia. MRI revealed lesions in the pons and both cerebellar hemispheres. CSF analysis demonstrated the presence of OCB. She had received a second dose of the Sars-CoV-2 vaccine 10 days before symptom onset. She showed clinical and radiological improvement with corticosteroids. Conclusion Transient demyelination following conventional doses of radiotherapy may occur in individuals susceptible to white matter disorders or with concurrent risk factors, warranting particularly careful evaluation in patients with pre-existing demyelinating diseases prior to initiating radiotherapy.