Imaging in viral infections of the central nervous system: can images speak for an acutely ill brain?

Viral infections involving the central nervous system (CNS) may result from a wide variety of agents and have clinically overlapping manifestations. The diagnosis is often made based on a combination of the clinical exam, local epidemiology, imaging, and biochemical findings. Despite the advances in medicine and imaging, the diagnosis often remains elusive. Imaging, however, still plays a vital role in suggesting the diagnosis in typical cases, excluding potential mimics, and in evaluating changes with therapy. Herein, the authors present a review of various common and rare viral encephalitides with emphasis on the imaging literature.