Case - Herpes Virus Encephalitis (Stroke Mimic)
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Herpes Virus Encephalitis is another stroke mimic.
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The patient's usually present with seizures,
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behavioral changes, fever,
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it usually involves the bilateral limbic system,
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the temporal lobe, the insula,
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and the cingulate gyrus.
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Remember, herpes is necrotizing encephalitis,
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so it has restricted diffusion
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due to cytotoxic edema.
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And because it's necrotizing,
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usually, the patients end up with encephalomalacia change,
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findings don't reverse.
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These are images of a 36-year-old female with
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mental status changes,
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and on the diffusion-weighted images,
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you can see restricted diffusion in the left
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greater than right temporal lobes,
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the anterior frontal lobes,
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the cingulate gyrus region,
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and the left greater than right insula.
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These are images of a 67-year-old male who
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had bizarre behavior, fever, and seizure.
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On the diffusion-weighted images,
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you can see restricted diffusion in the mesial temporal lobe,
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as well as the more lateral temporal lobe,
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so not arterial distribution.
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This would be anterior choroidal artery and PCA.
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This would be MCA and there's also
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involvement of the insula,
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extending up a little bit into the frontal operculum.
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Don't clearly see anything on the left side,
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maybe mesial temporal lobe and insula,
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but that's a little nebulous,
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and we're going to look
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on the post-gado images.
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And let's look at the FLAIR images first and you can
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see there's FLAIR hyperintensity
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in the same region,
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and there's a little bit of swelling and...
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don't clearly see anything on the other side.
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Let's look at the post-gado images and...
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don't see any parenchymal enhancement.
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There may be a little bit of
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venous congestion,
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leptomeningeal enhancement
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but no parenchymal enhancement.
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Later on in herpes,
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over after a week or so,
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as the blood-brain barrier breaks down,
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you can get gyriform enhancement.
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And then when we look at the Bravo sequences,
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we want to make sure we don't have venous sinus
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thrombosis, and you can see that the superior
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sagittal sinus and the transverse sinuses
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enhance normally.
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I'm also going to look at some susceptibility sequences.
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I'm kind of thinking these little temporal lobe
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seizures, behavioral changes,
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that this might be herpes.
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I do see one focus of hemorrhage in the insula,
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so that leads me to think herpes.
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He also had fever and seizures.
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The other thing would be an autoimmune encephalitis.
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But his PCR was positive for herpes.
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So, classic case of herpes
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involving the mesial temporal lobe,
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insula, limbic system,
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questionable lesions on the other side,
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and a positive PCR.
Pamela W Schaefer, MD, FACR
Professor of Radiology, Vice Chair of Education
Massachusetts General Hospital
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