Status Epelipticus, CJD, and Encephalitis
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Let's summarize the findings in herpes encephalitis,
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as one of the diagnoses that is going to be
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made pretty much exclusively by MRI scanning.
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The CT scan findings are typically normal,
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because the abnormality is relatively subtle.
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Herpes will present with fever in 90 percent of cases.
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You'll see it in the peri-insular region,
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as well as in the medial temporal lobes,
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as well as in the cingulum on either side of
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the corpus callosum in the medial frontal lobes.
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Hemorrhage occurs in about one-third of cases, and
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it's usually a bilateral, although asymmetric, process.
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Here, we see that the medial temporal lobe looks
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pretty good on the left side compared to the
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right side, but in the peri-insular region,
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we see bilateral disease in this patient.
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Another entity that may lead to
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seizures and fever is this entity.
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So here, we have diffusion-weighted imaging
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showing high signal intensity in the cortex.
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And this is a bilateral process.
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It's a little bit asymmetrical.
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In a patient who is having status epilepticus,
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you can see cytotoxic edema of the gray matter,
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which will reverse without permanent damage.
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So, in a patient who is actively seizing in the
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MRI scanner, has recently stopped seizing,
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or is being controlled in status epilepticus,
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this is a pattern that you may see that is
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limited to the cortex as cytotoxic edema on DWI.
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However, the differential diagnosis includes
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those entities that cause encephalitis,
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which include a number of viral etiologies,
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including things like measles, or mumps, or rubella,
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or other infectious etiologies, West Nile virus,
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etc. All of these can cause cortical edema.
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So the differential diagnosis is: does the patient
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have a primary seizure disorder, and what we're
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seeing is cytotoxic edema secondary to recent
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seizures, or does this patient have encephalitis?
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And we're seeing cytotoxic
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edema because of the infection.
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Obviously, this is easier made by the
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clinicians, because if the patient has a
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fever, we're more likely to have encephalitis.
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If the patient has a known seizure disorder that's
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out of control, or if the patient has stopped taking
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their seizure medications, then that might be the
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reason why the patient is in status epilepticus.
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In this case, I fooled you.
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This is a patient who has
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Creutzfeldt-Jakob disease, CJD.
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CJD is a disease entity that is due to an
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infectious prion particle, and it can lead to
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seizures, fever, as well as acute mental status
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changes and a rapidly developing encephalopathy.
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CJD most commonly affects the cortex.
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And second, most commonly affects the deep gray matter.
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However, sparing of the deep gray matter should not
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dissuade you from suggesting the diagnosis of CJD.
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Unfortunately, at this time in 2021, we really
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don't have any good medication for treating CJD.
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It's just expectant therapy with
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anti-seizure medications, etc.
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So this is a patient who has encephalitis, and
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that encephalitis is what we call a neurodegenerative
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disorder of Creutzfeldt-Jakob disease.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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