Salmonella Typhi Bacteremia and Mild Encephalitis with a Reversible Splenial Lesion

Cerebrospinal fluid studies showed 1 × 106/L WBCs, protein of 0.26 g/L, glucose of 3.4 mmol/L, negative gram stain, and negative viral PCR for herpes simplex virus 1 and 2. Infectious causes of MERS include numerous viral (adenovirus, Chikungunya virus, dengue virus, Epstein–Barr virus, influenza A and B viruses, and rotavirus) and bacterial (Enterococcus faecalis, Staph aureus, and Mycoplasma pneumoniae) pathogens.1–3 Kobuchi et al. described a case of MERS secondary to Salmonella enteritidis in an 8-year-old Japanese patient, but MERS as a manifestation of S. typhi infection has not previously been reported to the best of our knowledge.3 How diverse pathogens result in a common clinicoradiologic entity is incompletely understood. The homogenous, diffusion-restricting lesion characteristic of MERS is consistent with cytotoxic edema and is similar to lesions seen in familial hemiplegic migraine and venous sinus occlusion.4 Cytotoxic edema is thought to be the result of an inflammatory cytokine cascade triggered by infection.5,6 Hyponatremia accompanies many presentations of MERS, including our case, and may contribute to the intracellular edema.7 The predilection for the splenium is not completely understood, but may be related to a higher density of cytokine and glutamate receptors, density of interhemispheric fibers, and a relative lack of adrenergic tone. Lara J. Cooke, MD, MSc, FRCPC, Division of Neurology, Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, UCMC Area 3, 3350 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.