Probable Bacterial Meningoencephalitis Presenting With Reversible White Matter Restricted Diffusion: A Case Report

Bacterial meningoencephalitis typically presents with fever and altered mental status, and neuroimaging is frequently normal.We report an 82-year-old man with diabetes mellitus and chronic kidney disease who was found unresponsive at home.He was febrile on arrival with a Glasgow Coma Scale (GCS) score of 3/15.Initial investigations showed acute kidney injury, raised inflammatory markers, and rhabdomyolysis, and a computed tomography (CT) scan of the brain was unremarkable.Subsequent magnetic resonance imaging (MRI) of the brain showed bilateral, symmetrical restricted diffusion in the centrum semiovale and periventricular deep white matter, an appearance that suggested toxic metabolic encephalopathy (TME).Thereafter, cerebrospinal fluid (CSF) analysis showed a neutrophil-predominant pleocytosis with raised protein, but Gram stain, cultures, and viral polymerase chain reaction (PCR) studies were negative.Hence, the diagnosis made was probable bacterial meningoencephalitis.He was then started on ceftriaxone, ampicillin, and acyclovir.A repeat MRI after one week showed complete resolution of the diffusion abnormality.Despite this, the patient's level of consciousness did not improve, and he developed recurrent hypotension and worsening renal function and subsequently demised.This case demonstrates that reversible white matter diffusion restriction may be mistaken for a pure metabolic process and may mask an underlying meningoencephalitis.Therefore, in a febrile, encephalopathic patient, clinical judgement should take precedence, prompt early lumbar puncture (LP) should be performed where indicated, and imaging resolution should not be taken as a sign of clinical recovery.