Volume 52, Issue 6, Pages 606-614 (June 2015) Acute Pediatric Encephalitis Neuroimaging: Single-Institution Series as Part of the California Encephalitis Project  Julie Bykowski, MD, Peter Kruk, MD, Jeffrey J. Gold, MD, PhD, Carol A. Glaser, DVM, MD, Heather Sheriff, BA, John R. Crawford, MD, MS  Pediatric Neurology  Volume 52, Issue 6, Pages 606-614 (June 2015) DOI: 10.1016/j.pediatrneurol.2015.02.024 Copyright © 2015 Elsevier Inc. Terms and Conditions

Figure 1 Examples of increasing complexity of imaging findings for rank analysis. Predetermined ranking of imaging complexity included: (1) normal (not shown), (2) meningeal enhancement (A, post-contrast T1-weighted imaging, arrowheads) and/or focal T2-hyperintense lesion, (3) multifocal T2-hyperintense lesions (B, fluid-attenuated inversion recovery, arrows), (4) confluent T2-hyperintense lesions (C, fluid-attenuated inversion recovery, arrows), or (5) T2-hyperintense lesions plus diffusion restriction (D, apparent diffusion coefficient, arrows), hemorrhage, or hydrocephalus. Pediatric Neurology 2015 52, 606-614DOI: (10.1016/j.pediatrneurol.2015.02.024) Copyright © 2015 Elsevier Inc. Terms and Conditions

Figure 2 Atypical imaging with confirmed pathogen. Herpes simplex virus-1 was confirmed in these two patients. Images (A-D) are from a 16-month-old African American girl with fever and protracted vomiting. Magnetic resonance imaging shows T2 prolongation (A, fluid-attenuated inversion recovery, arrows) and diffusion restriction (B, apparent diffusion coefficient) in the right greater than left frontal lobes with corresponding meningeal and parenchymal enhancement (C, postcontrast T1-weighted image). Temporal lobes were not involved. Length of hospitalization was 7 days, and she completed 3-week course of acyclovir. A 2-month follow-up fluid-attenuated inversion recovery (D) confirms necrosis in the area of prior cortical infarct (arrowhead) with confluent T2 prolongation in both the frontal and parietal lobes (arrows). Images E-H are from a 1-year-old Asian boy with both limbic and extratemporal involvement including the right frontal lobe and insula (arrow) and thalami (arrowheads) evident on fluid-attenuated inversion recovery (E) and apparent diffusion coefficient maps (F), with cortical contrast enhancement (G). Length of hospitalization was 21 days. A 1-month follow-up fluid-attenuated inversion recovery (H) confirms necrosis in the area of prior infarct (arrows). Pediatric Neurology 2015 52, 606-614DOI: (10.1016/j.pediatrneurol.2015.02.024) Copyright © 2015 Elsevier Inc. Terms and Conditions

Figure 3 “Possible” status was attributed to pathogens identified in non-central nervous system samples. T2 hyperintense edema (A, fluid-attenuated inversion recovery, arrows), diffusion restriction (B, apparent diffusion coefficient, arrows) and hemorrhagic susceptibility (C, T2*/gradient echo sequence, arrows) is seen in the thalami of this 8 year old in whom parainfluenza 3 was identified on respiratory screening after 5 days of fever, cough, and vomiting progressing to altered mental status. Images (D-F) are from a 4 year old with fever and intermittent ataxia in whom Rhinovirus was identified on screening panel. Note that although T2 prolongation in the left midbrain (D, fluid-attenuated inversion recovery, arrowhead) also shows diffusion restriction (E, diffusion-weight imaging; F, apparent diffusion coefficient, arrowheads), the area of T2 prolongation in the right temporal lobe (C, arrow) remains hyperintense on apparent diffusion coefficient (F, arrow). Mycobacterium pneumoniae was identified in a 14 year old with an upper respiratory infection and fever proceeding to respiratory failure and altered mental status. Magnetic resonance imaging at presentation showed focal T2 hyperintensity (G, fluid-attenuated inversion recovery), diffusion restriction (H, diffusion-weight imaging), and enhancement (I, postcontrast T1-weighted imaging) in the inferior medulla (arrows). Pediatric Neurology 2015 52, 606-614DOI: (10.1016/j.pediatrneurol.2015.02.024) Copyright © 2015 Elsevier Inc. Terms and Conditions

Figure 4 Unknown pathogen. No etiology was identified for these three patients. Multifocal T2 prolongation was evident on fluid-attenuated inversion recovery in this 9 year old presenting with seizure, with involvement of the left cerebral peduncle (A, arrow), left caudate (B, arrow), right thalamus and posterior limb of the internal capsule (B, arrowheads), and additional patchy areas of T2 prolongation and mass effect in the subcortical and deep white matter (A-C). Brain biopsy and metabolic evaluation were also negative. Images (D-F) show cerebellar edema on fluid-attenuated inversion recovery (D, arrows) with corresponding hyperintensity rather than diffusion restriction on apparent diffusion coefficient maps (E, arrows) in this 12 year old who also required shunting for the associated hydrocephalus (F, postcontrast T1-weighted imaging, arrowheads). Children with unknown etiology also had complex imaging presentations, as in this 7 month old with confluent T2 prolongation (G, fluid-attenuated inversion recovery) involving the basal ganglia, thalami, corpus callosum, and deep white matter, with associated diffusion restriction (H, apparent diffusion coefficient, arrows) and thalamic hemorrhage (I, T2*/gradient echo sequence, arrows). Pediatric Neurology 2015 52, 606-614DOI: (10.1016/j.pediatrneurol.2015.02.024) Copyright © 2015 Elsevier Inc. Terms and Conditions