EC Paediatrics

Acute necrotizing encephalitis (ANE) is a rare and severe neurological complication predominantly affecting children, typically following viral infections, most commonly Influenza A. It is characterized by bilateral and symmetric brain lesions, mainly involving the thalami, with possible hemorrhagic transformation. We report the case of a previously healthy 5-year-old girl admitted to the intensive care unit for acute febrile altered consciousness occurring two days after a flu-like illness. Nasopharyngeal PCR was posi- tive for Influenza A virus. Brain computed tomography (CT) revealed bilateral symmetric hypodense thalamic lesions with brainstem involvement. Magnetic resonance imaging (MRI) confirmed the diagnosis by demonstrating bilateral thalamic and subcortical signal abnormalities with diffusion restriction and hemorrhagic components on susceptibility-weighted imaging. This case highlights the crucial role of imaging, particularly MRI, in the early diagnosis of this rare but potentially fatal condition.

Keywords: Acute Necrotizing Encephalitis; Influenza A; Pediatric Neuroradiology; Thalamus; MRI; Post-Viral Encephalopathy

1. Mizuguchi M. “Acute necrotizing encephalopathy of childhood”. Brain and Development 19 (1997): 81-92.
2. Wong AM., et al. “Acute necrotizing encephalopathy of childhood”. American Journal of Neuroradiology 27 (2006): 1919-1923.
3. Mizuguchi M., et al. “Acute necrotising encephalopathy of childhood: a new syndrome presenting with multifocal, symmetric brain lesions”. Journal of Neurology, Neurosurgery and Psychiatry 5 (1995): 555-561.
4. Neilson DE. “The interplay of infection and genetics in acute necrotizing encephalopathy”. Current Opinion in Pediatrics 6 (2010): 751-757.
5. Neilson DE., et al. Nature Genetics 41 (2009): 445-447.
6. Bassuk AG., et al. American Journal of Neuroradiology 24 (2003): 1766-1768.
7. Albayram S., et al. “Diffusion-Weighted MR Imaging Findings of Acute Necrotizing Encephalopathy”. American Journal of Neuroradiology 25 (2004): 792-797.
8. Kim JH., et al. “Acute necrotizing encephalopathy in Korean infants and children: imaging findings and diverse clinical outcome”. Korean Journal of Radiology 3 (2004): 171-177.
9. Yoshikawa H., et al. Pediatric Neurology 21 (1999): 585-589.
10. Okumura A., et al. “Outcome of acute necrotizing encephalopathy in relation to treatment with corticosteroids and gammaglobulin”. Brain and Development 3 (2009): 221-227.
11. Neilson DE. “Acute necrotizing encephalopathy: an expanding spectrum”. Pediatric Neurology 109 (2020): 14-22.
12. Okumura A, Mizuguchi M., et al. “Clinical features and outcomes of RANBP2-associated ANE”. Brain and Development 37 (2015): 847-854.
13. Sugaya N., et al. “MRI patterns and prognostic factors in pediatric ANE”. Journal of Child Neurology 34 (2019): 123-130.
14. Wong AM., et al. “Hemorrhagic thalamic involvement predicts poor outcome in ANE”. American Journal of Neuroradiology 27 (2006): 1919-1923.
15. Yamamoto Y., et al. “Radiological progression despite immunotherapy in ANE”. Pediatric Radiology 47 (2017): 1543-1550.
16. Wu X., et al. “Immunomodulatory strategies in ANE: review of case series”. Frontiers in Pediatrics 9 (2021): 652345.
17. Wu Y., et al. “MRI evolution in severe post-influenza ANE”. European Journal of Paediatric Neurology 22 (2018): 1119-1125.
18. Okumura A. “Therapeutic challenges in severe ANE: corticosteroids, IVIG, and plasma exchange”. Brain and Development 41 (2019): 781-790.