Ring-enhancing brain lesions: Listeria monocytogenes abscesses

An 82-year-old woman with a history of bilateral temporal arteritis and atrial fibrillation presented with short-term memory loss and feeling of being off-balance the previous 1 week. She could not remember her grandchildren’s names and birthdays, which her family deemed unusual. Neurological evaluation a year prior to admission did not show dementia or any other alarming neurological symptoms. The patient had a head computed tomography (CT scan) without contrast 2 days prior to admission with neurology that was concerning, and she was subsequently sent to our emergency department (ED) (Fig. 1a). She had biopsy-proven bilateral temporal arteritis 3 months prior to admission, and had been on a prednisone taper since. The vital signs on admission included: 35.9 C (96.7), 166/79 mmHg, 65 beats/min, 17 breaths/min, 96 % oxygen saturation on room air, and body mass index of 24. The physical examination was unremarkable except for a moon facies, facial erythema, irregular irregular heart rate and rhythm, and right eye blindness. The patient was oriented to self, not time, and could name and slowly follow commands. Cranial nerves 2–12 were grossly intact. Strength 5/5 in all limbs, but the patient was slow with movements. Sensation was grossly intact. Repeat head CT with contrast was performed and revealed three ring-enhancing lesions of the biparietal–occipital lobes surrounded by vasogenic edema and effacement of the occipital horn of the left lateral ventricle (Fig. 1b). There was no evidence of hemorrhage, midline shift, or acute infarct. The head CT scan without contrast prior to admission showed two ringenhancing lesions (Fig. 1a). RPR, toxoplasma antibody, and HIV were all negative. Blood cultures revealed 1 of 2 Gram-positive rods, later confirmed as Listeria monocytogenes (Fig. 1c). Culture of the brain lesion biopsy further confirmed L. monocytogenes brain abscesses (Fig. 1d). The patient was switched from empiric vancomycin, ceftriaxone, and metronidazole to ampicillin 2 g IV Q4H to be continued for 6–8 weeks. In patients presenting to the ED with acute confusion, neurological decline or deficits, or any other change in mentation, thorough clinical examination and neurological imaging are vital for proper medical workup. There are many possible culprits of ring-enhancing lesions such as radiation necrosis, metastasis, abscess, glioblastoma multiforme, subacute infarct, contusion, or lymphoma. It is imperative to delineate the cause of the ring-enhancing lesion, as the treatment varies extensively among the aforementioned causes. Groups at risk for listerial infection include pregnant women, immunocompromised, elderly, or debilitated adults with underlying diseases. Ingestion of listeria-contaminated food is likely the source of infection in all human listerial infections. In our case a particular brand of ice cream consumed by the patient with a recent history of United States listeria outbreak remains the likely culprit. In the immunocompetent human, L. monocytogenes exposure usually results in self-limited, febrile diarrheal gastroenteritis lasting 1–3 days. In the immunocompromised, gastrointestinal invasion can lead to bacteremia, with a predilection for the CNS, where it can cause meningitis, meningoencephalitis, or rhombencephalitis [1]. Although L. monocytogenes is a well-known cause of meningitis and encephalitis, brain abscesses caused by this organism are highly uncommon and reported to occur in & Andrew C. Berry aberry5555@gmail.com