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AJNR Awards, New Junior Editors, and more. Read the latest AJNR updates

Case of the Month

Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO

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February 2021
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Next Case of the Month Coming March 9...

Acute Necrotizing Encephalopathy (ANE) Secondary to Dengue Infection

  • Background:
    • ANE is triggered mainly by viral infections, and CNS manifestations can be attributed to neurotropic effects, postinfectious sequelae, and secondary to the systemic (parainfectious) manifestation, which is the main pathophysiologic mechanism in the case of encephalitis and was the triggering factor in our case.
    • MRI angiography and venography (without occlusions or thrombosis) and serology were performed for diagnostic investigation for our patient, with emphasis on serologic research of the viral etiology of COVID-19 (negative), herpes (negative), and dengue (positive).
  • Clinical Presentation:
    • Systemic manifestations of dengue, such as myalgia, fever, frontal/retro-orbital headache, vomiting, and skin and neurologic rash, such as convulsive crises, lowering the level of consciousness
  • Key Diagnostic Features:
    • The imaging appearance is characterized by T2-hyperintense swelling in the basal ganglia, thalami, cerebellar hemispheres, and brain stem.
    • The presence of hyposignal in the SWI at the center of thalamic lesions, due to petechial hemorrhages, has been termed the “double donut sign.” This is a typical MRI finding in cases of dengue encephalitis and can be considered a diagnostic characteristic if the clinical criteria for dengue encephalitis are met, which are: fever, acute signs of neurologic involvement, presence of IgM antibodies in the blood or CSF, and exclusion of other causes of viral encephalitis or encephalopathy.
  • Differential Diagnoses
    • COVID-19–associated acute hemorrhagic necrotizing encephalopathy
    • Japanese encephalitis
    • Chikungunya encephalitis
    • Herpetic encephalitis
  • Treatment:
    • Mainly supportive

Suggested Reading

  1. Kumar AS, Mehta S, Singh P, et al. Dengue encephalitis: “double doughnut” sign. Neurol India 2017;65:670–71
  2. Shah N, Nair AV, Ahamed S, et al. Dengue doughnut: a diagnostic magnetic resonance imaging finding in dengue encephalitis. J Postgrad Med 2018;64:127
  3. Bhanuprakash E, Anukapoor, Laxmi S. "Double doughnut“ sign in dengue encephalitis - a unique MRI finding. International Journal of Science and Research 2019;8:1247–49

Current Issue

American Journal of Neuroradiology: 46 (6)
American Journal of Neuroradiology
Vol. 46, Issue 6
1 Jun 2025
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