Views and Reviews Neuroimaging of Pediatric Intracranial Infection—Part 2: TORCH, Viral, Fungal, and Parasitic Infections Joshua P. Nickerson, MD, Beat Richner, MD, Ky Santy, MD, Maarten H. Lequin, MD, Andrea Poretti, MD, Christopher G. Filippi, MD, Thierry A.G.M. Huisman, MD From the Divisions of Neuroradiology (JPN) and Pediatric Radiology (AP, TAGMH), Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, Baltimore, MD; Divisions of Pediatrics (BR) and Pediatric Imaging (KS), Jayavarman VII Kantha Bopha Hospitals, Siem Reap, Cambodia; Division of Pediatric Radiology, Sophia Children’s Hospital, Erasmus University Rotterdam, the Netherlands (MHL); Division of Pediatric Neurology, University Children’s Hospital, Zurich, Switzerland (AP); and Department of Neuroradiology, The University of Vermont/Fletcher Allen Healthcare, Burlington, VT (CGF). Keywords: Pediatric intracranial infec- tions, children, ultrasound, magnetic res- onance imaging, susceptibility-weighted imaging, diffusion-weighted imaging, dif- fusion tensor imaging, magnetic reso- nance spectroscopy. Acceptance: Received August 20, 2011, and in revised form October 27, 2011. Accepted for publication December 15, 2011. Correspondence: Thierry A.G.M. Huisman, MD, EQNR, FICIS, Division of Pediatric Radiology, Russell H. Morgan Department of Radiology and Radiologi- cal Science, Johns Hopkins Hospital, 600 North Wolfe Street, Nelson Basement B-173, Baltimore, MD 21287-0842. E-mail: thuisma1@jhmi.edu. J Neuroimaging 2012;XX:1–13. DOI: 10.1111/j.1552-6569.2011.00699.x ABSTRACT In the second half of this 2-part review, the neuroimaging features of the most common viral, fungal, and parasitic infections of the pediatric central nervous system are discussed. Brief discussions of epidemiology and pathophysiology will be followed by a review of the imaging findings and potential differential considerations. Introduction As discussed in the first part of this review on pediatric central nervous system (CNS) infections, the pediatric radiologist or neuroradiologist who routinely reads pediatric studies must be familiar with the variable appearance of pediatric CNS infec- tions. Having discussed the various imaging modalities avail- able and the manifestations of bacterial infections (part 1), at- tention is turned to the viral infections and their sequelae, as well as fungal and parasitic infections. Before individual infectious agents are presented, a brief dis- cussion of imaging patterns and manifestations of broad disease classifications is warranted. Certain classes of pathogens have a predilection for particular anatomic regions, and the imag- ing findings subsequently may be predictive of the infectious agent. For example, herpes simplex virus (HSV) is well known to preferentially affect the temporal and frontal lobes, fungal infections often involve the central gray matter, Haemophilus in- fluenzae is seen to predominantly affect the subcortical regions, and cytomegalovirus (CMV) typically spares the subcortical U-fibers while affecting the remainder of the cerebral white matter. These preferential tissue involvements are helpful when faced with an imaging study in which many of the findings may be nonspecific. Frequently, the imaging patterns associated with the infectious agents are a result of the method through which that agent gains access to the CNS. Aside from the obvious differences between direct invasion from adjacent structures and delivery via the bloodstream, the antigens presented by different agents may result in their preferential deposition in various brain regions. Tissue damage is in many cases due not only to the endotoxins associated with the pathogen but to the associated inflammatory response of the host immune system. Congenital Viral Infections Prenatal, intrauterine viral infections of the CNS are unique because the fetal immune system is immature and the brain is rapidly developing. Interference with the various devel- opmental processes, for example, myelination, migration, or cortical organization may result in various presentations on Copyright ◦ C 2012 by the American Society of Neuroimaging 1