Pediatric Herpes Simplex Virus-1 Encephalitis

• Etiology: Necrotizing hemorrhagic encephalitis that is localized in limbic system
• Imaging:
  — Lesions typically in temporal lobe and are medial before lateral in location with extra-temporal regions in 40% of children
  — Asymmetric brain damage – unilateral or bilateral
  — Gray matter usually before white matter
  — Extension to insula and orbital surface of frontal lobes and cingulate gyrus and thalamic lesions: children with parietal or opercular lesions (probably related to the existence of numerous thalmo-cortical connections)
• Imaging CT:
  — Often normal in first 2-3 days
  — Later see diffuse mild edema and swelling
• Imaging MRI:
  — Shows gyral edema
  — May be hemorrhagic
  — T1WI post enhancement: With or without enhancement in early stage
  — T2WI: Temporal lobe hyperintense
  — FLAIR: Temporal lobe hyperintense
• DDX:
• Complications:
• Treatment:
• Clinical: In older child or adult

Radiology Cases of Herpes Simplex Virus-1 Encephalitis