CASE 1 : Listeria Rhombencephalitis (Brainstem Encephalitis) with Brain Abscess
A 44 year old man from rural Wisconsin presented with progressive ataxia, diplopia , fatigue and fevers and chills . He was otherwise ,an healthy dairy farmer. Since admission - he had a rapid worsening of his sensorium requiring intubation. His MRI revealed small ring enhancing lesions in the right cerebellum and pons consistent with microabscesses. CSF exam revealed 39 WBC's 43%PMN's and 31% Lymphocytes, glucose of 54 and protein of 71. CSF HSV,VZV PCR's and crypto antigens were negative. CSF and blood cultures later returned positive for Listeria monocytogenes.
1. CNS Listeriosis : Unlike other organisms that cause bacterial meningitis frequently ( Strep pneumonie, Neisseria and Haemophilus), Listeria has a tropism for the brain parenchyma itself , particularly the brain stem, as well as meninges. CSF features particular to Listerial Meningitis include subacute presentation, fluctuating mental status (75%), positive blood cultures (50-75%) and normal CSF glucose (>60%).
2. Brainstem Encephalitis (Rhombencephalitis): In contrast to other listerial CNS infections, these occur in healthy adults. Typical clinical picture is of a bi-phasic illness with fevers, headaches lasting 3-4 days followed by abrupt onset cranial nerve deficits and cerebellar signs . 2/3rd s of patients are bacteremic .
3. Treatment : Bacteremic patients without CSF abnormalities can be treated for 2 weeks with Ampicillin .Gentamicin is added for synergy in patients with CNS listeriosis and those immunecompromised . Patients with rhombencephalitis or brain abscess should be treated for at least 6 weeks . In a nonrandomized study of 22 patients with severe listerial meningoencephalitis, TMP-SMX plus ampicillin was associated with a much lower failure rate and fewer neurologic sequelae than ampicillin combined with an aminoglycoside (Merle-Melet M, J Infect. 1996;33:79-85.)
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