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.