Treatment-related MR features of the brain

Various brain MR abnormalities may develop during or after surgery, radiochemotherapy, and medical treatment. Postoperatively, characteristic or nonspecific imaging changes may reflect such conditions as hemorrhage, edema, infarction, or abnormal contrast enhancement. Radiation therapy may induce white matter abnormality or radiation necrosis, which is often difficult to differentiate from tumor recurrence or dissemination. Drug-induced abnormalities include leukoencephalopathy related to the intrathecal injection of methotrexate, T1 shortening of the basal ganglia and pituitary gland due to long-term hyperalimentation therapy, reversible subcortical white matter involvement caused by immunosuppressive agents such as cyclosporine and tacrolimus, sinus thrombosis related to the use of oral contraceptives and tamoxifen, and lesion of the splenium related to antiepileptic drugs. It is important to be familiar with these MR features for making the differential diagnosis, evaluating the results of the treatment, and avoiding unnecessary additional imaging studies.