Case: Listeria Rhombencephalitis on MRI
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This is yet another patient who
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presented with fever and seizures.
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In this case, the abnormality is relatively well
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localized to the pons and the midbrain junction.
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There may be some extension into the middle
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cerebellar peduncles, and the
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pons appears to be expanded.
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Now, our differential diagnosis would include
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vitamin C and D deficiency, right? Vascular? Unlikely,
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because it's extending into the middle cerebellar
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peduncles, and the patient didn't present with a neurologic
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deficit but presented with fever and seizures.
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Infectious etiologies, for sure, were in that category.
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Trauma? No. Acquired? No. Metabolic?
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Unlikely to be osmotic demyelination.
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It's not central.
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It's going out into the middle
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cerebellar peduncles. Neoplastic?
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Well, you can have pontine gliomas,
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astrocytomas, etc.
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They wouldn't generally present with
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seizures and fever. Congenital? And drugs?
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So, drug-related things can occur here as well.
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In this case, because the patient presented with fever,
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the patient underwent lumbar puncture to get CSF, and
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it was an inflammatory CSF, suggesting an infection.
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Here is the post-gadolinium enhanced
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scan, and what you see are just fine
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little dots of contrast enhancement
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in the central aspect of the pons. This
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was also demonstrated here on the coronal
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post-gadolinium scan. There is some faint
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enhancement in the central aspect of the pons.
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When you have an infectious inflammatory condition
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that is relatively specific to the brainstem, we call
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that a rhombencephalitis, referring to the rhombencephalon,
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which is that portion of the posterior
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fossa structures in the development of the brain.
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So, the infectious agents that have
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preference for the rhombencephalon are
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Listeria monocytogenes, as well as tuberculosis.
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Now, tuberculosis usually doesn't present
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as sort of this diffuse process. It usually
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has a focal lesion within the pons.
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This type of diffuse process in the
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pons, with expansion and enhancement,
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is more characteristic of Listeria.
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The importance of suggesting the
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diagnosis of Listeria is that
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this is a very fastidious microorganism—
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a bacterium that's hard to grow in culture.
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Therefore, if you alert the microbiology team
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that you're concerned about Listeria, they may be
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able to do certain things to enhance its growth and
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confirm the diagnosis, as opposed to just giving them
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the sample without any history, in which case
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it may not grow in culture as readily.
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The differential diagnosis here might include something
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called CLIPPERS syndrome, which is an entity that is
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associated with a vasculopathy and inflammatory
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change in a patient who may have lymphoma.
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This was Listeria rhombencephalitis.
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Across the continents, across the globe,
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the most common infection to affect the
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brainstem is going to be tuberculosis,
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because that is much more prevalent in society
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globally than, for example, in the United States.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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