Methotrexate-induced acute encephalopathy in children: MRI findings and clinical features

Objective: To evaluate the MRI findings and clinical features of methotrexate induced acute encephalopathy in children. Methods: The clinical data and brain MRI obtained in 13 children with methotrexate induced acute encephalopathy were retrospectively reviewed. The MRI features were analyzed, including information on the location, the signal intensity and follow-up MRI study was performed. Results: Of the 13 patients, 2 patients suffered from seizure. Five patients had dysphasia, of which 4 patients had evidence of hemiparesis, 1 patient had right facial palsy. Five patients had unilateral weakness. And left hemiparesis was observed in 1 patient. DWI revealed well demarcated asymmetrical hyperintensity lesions within the centrum semiovale and/or periventricular white matter in 10 patients, corresponding to areas of hypointensity on ADC maps. One case showed hyperintensity areas in the bilateral supratentorial cortex and subcortical white matter on T₂-weighted images with subtle high intensity on DWI. In all 10 cases there were resolution of the diffusion abnormality, 8 cases displayed residual FLAIR signal abnormalities involving areas of previously seen diffusion restriction, 5 cases showed decreased range of the lesion, 1 case was progressive, and 2 cases were stable. One case with hyperintensity areas in the supratentorial cortex and subcortical white matter showed small residual hyperintensity on T₂-weighted images and resolution of the diffusion abnormality. Conclusions: MTX-induced acute encephalopathy often manifests as stoke-like symptoms. DWI is the imaging modality of choice for the detection of acute MTX neurotoxicity, and asymmetrical restricted diffusion in the deep white matter is the characteristic sign. Cytotoxic edema induced by MTX is transient and reversible. (authors)