Non-congenital viral infections of the central nervous system: from the immunocompetent to the immunocompromised child

Infection and inflammation: radiological insights into patterns of pediatric immune-mediated CNS injury

The central nervous system (CNS) undergoes constant immune surveillance enabled via regionally specialized mechanisms. These include selectively permissive barriers and modifications to interlinked innate and adaptive immune systems that detect and remove an inciting trigger. The end-points of brain injury and edema from these triggers are varied but often follow recognizable patterns due to shared underlying immune drivers. Imaging provides insights to understanding these patterns that often arise from unique interplays of infection, inflammation and genetics. We review the current updates in our understanding of these intersections and through examples of cases from our practice, highlight that infection and inflammation follow diverse yet convergent mechanisms that can challenge the CNS in children.

Epidemiology and Disease Burden of Hospitalized Children With Viral Central Nervous System Infections in China, 2016 to 2020

BACKGROUND

Viral central nervous system (CNS) infections seriously threaten the life and health of children, with a high mortality and severe sequelae in China and globally. Surveillance of viral CNS infections in children is important, especially in hospitalized children, to facilitate disease evaluation.

METHODS

In this study, we collected the data on the discharged Face Sheet of Medical Records from database from 2016 to 2020 and analyzed the epidemiologic characteristics and disease burden of hospitalized children (≤18 years old) with viral CNS infections in China. We classified the discharge diagnosis of viral CNS infection as viral encephalitis (VE), viral meningitis (VM), viral meningoencephalitis (VME), viral encephalomyelitis (VEM), and viral meningomyelitis (VMM).

RESULTS

A total of 42,641 cases of viral CNS infections were included in the database, consisting of 39,279 cases with VE (92.47%), 2011 cases with VM (4.73%), 1189 cases with VME (2.80%), 118 cases with VEM (0.28%), and 44 cases with VMM (0.10%). The number of hospitalized patients with viral CNS infections accounted for 0.74% (42,641 of 5,790,910) of all hospitalized cases. The onset of viral CNS infections presented seasonal characteristic, with peaks in June to July and December to January. Seizures are the most frequent complication of this disorder. Median length of stay and inpatient expenditures for patients with viral CNS infections were 9 days and 1144.36 USD. Causative viruses were identified in 4.33% (1848 of 42,641) of patients.

CONCLUSIONS

This study will help understand the clinical epidemiology and disease burden of hospitalized children with viral CNS infections in China.

Magnetic resonance imaging patterns of paediatric brain infections: a pictorial review based on the Western Australian experience

Paediatric brain infections are relatively uncommon, but it is important for radiologists to recognise the disease and provide accurate differential diagnoses. Magnetic resonance imaging (MRI) plays an important role in determining the most likely causative pathogen—either in the setting of an unwell child with acute infectious encephalitis, or in the evaluation of a child for sequela of prior infection. Image analysis can, however, be difficult since a particular pathogen can cause variable MRI findings across different geographic environments, and conversely, a particular appearance on MRI may be caused by a variety of pathogens. This educational review aims to identify some of the key MRI patterns seen in paediatric brain infections and present example cases encountered in Western Australia. Based on (i) the predominant type of signal abnormality (restricted diffusion versus T2 hyperintensity) and (ii) the distribution of signal abnormality throughout the brain, this review presents a framework of six key MRI patterns seen in paediatric brain infections, with an emphasis on acute infectious encephalitis. There is general utility to these MRI patterns—each suggestive of a group of likely diagnostic possibilities which can be calibrated according to institution and local environment. The pattern-based framework of this review can be easily transitioned into daily radiological practice, and we hope it facilitates the formation of accurate differential diagnoses in paediatric brain infections.