Literature

Clinical Pearls & Morning Reports

Posted by Carla Rothaus, MD

Published October 23, 2024

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How would you treat a brain abscess caused by Listeria monocytogenes?

The differential diagnosis for any patient with a newly discovered brain mass includes cancer, infection, autoimmune disease, vascular disease, a toxic–metabolic process, and congenital lesions. The severity and time course of symptoms are essential to narrowing the differential diagnosis. Read the NEJM Case Records of the Massachusetts General Hospital here.

Clinical Pearls

Q: Does Gram’s staining reliably differentiate gram-positive and gram-negative bacteria?

A: Specimens that undergo testing with Gram’s staining are subject to technical error and may be over-decolorized or under-decolorized during the staining procedure, which can lead to an erroneous result. Over-decolorization results in a gram-positive organism (purple) appearing pink, like a gram negative organism. Conversely, under-decolorization results in a gram-negative organism (pink) appearing purple, like a gram-positive organism.

Q: What is the classic pattern of ring-enhancement seen in patients with autoimmune disease of the central nervous system (CNS)?

A: Persons with a fulminant autoimmune disease such as tumefactive multiple sclerosis can present with lesions in the brain that exert mass effect and are associated with heterogeneous enhancement. It is important to note that the pattern of ring enhancement seen in patients with autoimmune diseases of the CNS is most often that of an incomplete or open ring.

Morning Report Questions

Q: Can CNS lymphoma and brain abscess be confused for one another?

A: Head imaging findings in patients with CNS lymphoma are typically characterized by intraparenchymal, multifocal, homogeneously enhancing lesions with associated restricted diffusion. However, in immunocompromised persons with CNS lymphoma, the appearance of a lymphomatous lesion may be atypical and can show ring enhancement with central necrosis that closely resembles high-grade glioma or abscess.

Q: How would you treat a brain abscess caused by Listeria monocytogenes?

A: Infection with L. monocytogenes can cause devastating CNS disease in high-risk persons, particularly in aging and immunosuppressed adults. Approximately half of brain abscesses of any cause result from contiguous spread of infection, and approximately a third result from hematogenous spread. L. monocytogenes penetrates the CNS by hematogenous spread from the gastrointestinal tract. The incubation period for CNS disease is approximately 9 days. Review of the literature suggests the best approach to brain abscess due to L. monocytogenes is neurosurgery in combination with a long course of antimicrobial therapy.

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Research summaries covering topics relevant to residents and trainees.