Case 7: Discussion

CASE 7: Discussion

CNS Infections

General

There are a number of different infections than can affect the central nervous system. Different types of infections have different CNS manifestations and therefore exhibit different patterns on imaging.

Encephalitis

  • General term that means diffuse or multifocal parenchymal inflammation
  • Wide variety of infectious agents cause encephalitis: viral is the most common
  • Imaging patterns vary with agent. The most common is HSV.

Herpes Simplex Encephalitis

  • Predilection for the limbic system:
    • Temporal lobes (medial and lateral)
    • Insular Cortex, internal capsule (spared basal nuclei)
    • Cingulate gyri (spreads from the hippocampus)
    • Subfrontal region
    • Cranial nerves (especially CN V)
    • May start unilateral, but typically spreads contralateral

Meningitis

  • Diagnosis: History, physical, CSF analysis
  • Role of Imaging: Monitor complications
    • Ventriculitis
    • Abscess
    • Vascular thrombsis (arterial or venous)
  • Most common imaging finding: Normal CT/MRI
  • May (but often don't see)
    • Increased meningeal enhancement
    • Subarachnoid exudate
    • Communicating hydrocephalus

Herpes encephalitis: photograph of a coronally sectioned gross specimen shows multiple petechial hemorrhages (arrowheads) and some granular atrophy of the insular cortex and the undersurface of the medial temporal lobe.

Smirniotopoulos J G et al. Radiographics 2007;27:525-551.

Cerebral Abscess

  • Evolves from focal inflammation of the brain parenchyma (cerebritis)
  • Pyogenic abscesses characteristically are peripherally enhancing collections that demonstrate diffusion restriction within the central portion of the abscess cavity.