Table 9

Neuroimaging patterns in herpes simplex encephalitis

ImagingPatterns
Herpes simplex encephalitis
 CTUsually normal, but can characteristically show reduced attenuation in the temporal lobes after the first week of the disease
 MRI
  • ▸ T2, FLAIR and DWI hyperintensities in the medial temporal lobes, the orbital surface of the frontal lobes, the insular cortex, the angular gyrus, and in the insulas early in the course

  • ▸ Abnormal areas may show enhancement with gadolinium

  • ▸ Midline shift may be present with large cerebral oedema

 SPECTIncreased tracer accumulation which reflects hyperperfusion possibly earlier than pathological signals appear on MRI
  • DWI, diffusion-weighted imaging; FLAIR, fluid-attenuated inversion recovery; SPECT, single-photon emission CT.