Acute necrotizing encephalopathy in a child during the 2009 influenza A(H1N1) pandemia: MR imaging in diagnosis and follow-up

Abstract

The recently emerged novel influenza A(H1N1) virus continues to spread globally. The clinical disease generally appears mild, but unfavorable outcomes have been reported. We describe a case of a 3-year-old Italian girl infected with influenza A(H1N1) virus presenting with neurologic deterioration. CT findings were negative, but MR imaging findings were consistent with ANE. To our knowledge, this is the first case reported in Europe and the second in worldwide pediatric radiology literature.

Fig 1.

Axial noncontrast CT image obtained on admission shows normal attenuation in the thalami.

Fig 2.

MR imaging in the acute stage. A, Axial T2-weighted image shows symmetric increased signal intensity in the thalami and supratentorial frontal white matter. B, Sagittal T2-weighted image demonstrates hyperintensity in the cerebellum and the brain stem, including the midbrain and dorsal pons. Note tonsillar herniation and hydrocephalus before shunt surgery. C, Sagittal T1-weighted MR image shows hypointensity in the thalami and cerebellar hemisphere. D, T2-weighted gradient-echo image reveals decreased signal intensity in the central portion of the thalami, indicating hemorrhagic necrosis. E and F, Axial DWI and an apparent diffusion coefficient color-coded map reveal restricted diffusion, with a concentric pattern, symmetrically involving the thalami.

Fig 3.

MR image obtained 10 days after admission. Sagittal T1-weighted MR image shows hyperintensity in the thalami and cerebellum, consistent with subacute hemorrhagic changes.

Fig 4.

MR imaging in the chronic stage, performed 40 days after admission demonstrates severe sequelae. A and B, Axial and coronal T2-weighted images reveal sharply marginated bilateral cavitation in the cerebellum and shrunken thalami. C–E, 3D views on a frontotemporal reconstruction depict fractional anisotropy in the pyramidal tracts (C) cerebellar hemispheres (D), and frontal white matter (E), showing destruction of the normal anisotropy.

Fig 4.

MR imaging in the chronic stage, performed 40 days after admission demonstrates severe sequelae. A and B, Axial and coronal T2-weighted images reveal sharply marginated bilateral cavitation in the cerebellum and shrunken thalami. C–E, 3D views on a frontotemporal reconstruction depict fractional anisotropy in the pyramidal tracts (C) cerebellar hemispheres (D), and frontal white matter (E), showing destruction of the normal anisotropy.