[Case of methotrexate encephalopathy: findings on diffusion tensor image and correlation with clinical outcome].

Methotrexate (MTX) is a major cause of treatment-related acute neurotoxicity. We report on clinical and imaging findings of reversibly restricted diffusion in a patient with transient encephalopathy after high dose MTX therapy for osteosarcoma. During the chemotherapy, a 19-year-old man was introduced for the evaluation of consciousness disturbance. Neurological examination revealed confusion, inability of speak at the onset On next day, there were still difficulties in swallowing and phonation, and furthermore deep tendon reflexes were hyperactive in bilateral lower limbs with positive Babinski responses bilaterally. By the 6th day, findings at neurological examination were completely normal. Initial imaging on presentation was performed using MRI. Diffusion weighted MRI clearly indicated areas of restricted diffusion within both centrum semiovale. These abnormalities were confirmed by the diffusion tensor (DT) technique (ADC and FA map). The follow-up MRI examinations using same protocol showed resolution of the ADC and FA abnormalities but increasing T2-signal changes. Neither contrast enhancement nor atrophy was encountered. Early detection of MTX white matter injury by DT image has the potential to alert the oncologist and neurologist to this event and provide a technique by which treatment of neurotoxicity can be monitored.