Conventional and diffusion-weighted MRI findings of methotrexate related sub-acute neurotoxicity

We describe longitudinal diffusion-weighted MRI findings of sub-acute leukoencephalopathy following methotrexate therapy in a 24-year-old man diagnosed with pre-B-cell acute lymphoblastic leukemia (ALL), presenting with right-sided paralysis and aphasia after second consolidation with intrathecal triple-drug therapy given intrathecally. This case demonstrates the value of DWI in evaluation and diagnosis of sub-acute toxic leukoencephalopathy in patients being treated with methotrexate. The longitudinal follow up DWI findings suggest reversible metabolic derangement rather than ischemia as the cause of these findings.