Uncommon acute neuroimaging findings in severe neonatal herpes simplex virus 2 and consequences of delayed diagnosis.

Neonatal herpes simplex virus (HSV) infection of the central nervous system (CNS) is an emergency that can have devastating structural consequences and clinical outcomes. As it presents non-specifically in neonates, it is difficult to rapidly diagnose without neuroimaging. Although once thought to cause widespread parenchymal destruction, neonatal CNS HSV infection may present with more focal parenchymal injury on neuroimaging, not involving the medial temporal lobes as in adults. We report a case of a three-week-old girl with herpes simplex virus type 2 (HSV-2) encephalitis with exclusive bilateral corticospinal and frontal opercular involvement, which remained undiagnosed and untreated until three months of age. Neuroimaging upon presentation to the emergency room demonstrates a highly suggestive pattern of severe neonatal CNS HSV-2 infection which followed the natural history on subsequent imaging, highlighting the importance of emergency neuroimaging as well as having a high index of suspicion for making the diagnosis.