Neuroradiology #39

• Subtle hypodensity in the medial temporal lobe on the right side.

• Sparing of the basal nuclei on the right side.

• Immediately call the ordering physician to communicate that the imaging (and clinical) findings are suggestive of Herpes Simplex Encephalitis.

  • This will prompt the clinician to directly start with an antiretroviral agent (acyclovir) if not started already and to perform a lumbar puncture to confirm HSV in CSF.

• T2 hyperintense regions with swelling/oedema and involvement of both white matter and cortex centered around the right sylvian fissure with involvement of the right temporal, frontal and insular region. Subtle patchy and leptomeningeal enhancement in the right temporal lobe can be seen.

Herpes Simplex Encephalitis

• The clinical picture is already highly suggestive of this diagnosis with supporting imaging findings. The diagnosis was confirmed with positive PCR for HSV-1 in CSF.

• Typical imaging findings of herpes encephalitis are T2(/FLAIR) hyperintense swollen areas of cortex and white matter with bilateral but asymmetrical involvement of the fronto-temporo-insular regions. Characteristic is sparing of the lentiform nuclei, which distinguishes it from ischemia due to vessel occlusion. Diffusion restriction and hemorrhage can be present.

• This is a radiological emergency and the phone must be picked up directly to alert the clinician and to prevent significant mortality and morbidity.

Reference:

• Frazier. Herpes Simplex Encephalitis. RadioGraphicsVol. 37, No. 1
• https://radiopaedia.org/articles/herpes-simplex-encephalitis?lang=us