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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.
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