Diffusion-weighted MR imaging findings of acute necrotizing encephalopathy

Abstract

Multiple, symmetrical brain lesions affecting the bilateral thalami and cerebral white matter, which often show a concentric structure on CT and MR images, characterize acute necrotizing encephalopathy (ANE) of childhood. We describe the imaging findings of a 2-year-old child with ANE obtained with diffusion-weighted MR imaging. We discuss the significance of these findings, as well as the pathophysiology of ANE lesions, with reference to the appearance of the disease as revealed by diffusion-weighted MR imaging.

Fig 1.

Conventional MR image findings in acute-stage ANE in 2-year-old-girl. A, Axial T2-weighted images show symmetric bilateral hyperintensities located deep in the cerebral-cerebellar white matter, bilateral thalami, and pontine tegmenta. B, Contrast-enhanced T1-weighted images reveal bilateral symmetric ringlike enhancement around the central hypointense portion of thalamic and central deep cerebral white matter lesions. Homogeneous enhancements in the pontine tegmenta and cerebellar white matter are also seen. C, T2-weighted gradient-echo MR image of the brain shows multiple, small hemorrhagic foci located on the central portion of thalamic lesions.

Fig 2.

Diffusion findings in acute-stage ANE in a 2-year-old girl. A, Diffusion-weighted MR images (b = 1000) show bilateral symmetric diffuse hyperintense lesions in the cerebellar-cerebral white matter, thalami, and pontine tegmenta. B, The ADC map shows three different patterns of the thalamus and cerebral white matter. The center of the lesions shows higher ADC values than those of normal parenchyma, the peripheral portion of central lesions shows very low ADC values, and outside the thalamus and cerebral white matter are high ADC values, findings compatible with vasogenic edema. Note that the splenium of corpus callosum, pontine tegmanta, optic radiatia, and cerebellar white matter have low ADC values in the central portion and high ADC values in the peripheral portion. C, Mean ADC values and pattern on the right thalamus (A, center of thalamic lesions; B, periphery of the central thalamic lesions; C, outside portions of the thalamic lesions).

Fig 3.

On follow-up MR examination, 25 days after onset of symptoms, T2-weighted (A) and fluid-attenuated inversion recovery (B) MR images of brain show neuronal tissue destruction on the central portion of cerebral white matter, bilateral optic radiation, deep cerebellar white matter, and pontine tegmanta. Necroses are also seen on the central portion of thalamus and deep cerebral white matter. T1-weighted MR image (C) shows subacute hemorrhagic changes in the central necrotic portion of thalamus.