A vanishing callosal lesion on brain imaging in a patient with meningoencephalitis

A 21-year-old previously healthy man had become progressively unresponsive five days after developing highgrade fever. On examination, he was unconscious (GCS 3/15), with equally reacting normal-sized pupils and normal optic fundi, and marked neck stiffness. His blood investigations showed neutrophil leucocytosis (total white cells 21,250/μl; 88% neutrophils) and serum sodium of 112 mmol/l. Magnetic resonance imaging of the brain was normal except for a non-enhancing focal hyperintensity on T2 and FLAIR sequences with diffusion restriction and low signal on ADC map in the splenium of the corpus callosum (Figure). Cerebrospinal fluid analysis showed polymorphocytic pleocytosis (225 cells/μl; 80% polymorphocytes), elevated protein (99 mg/dl) and a CSF: plasma glucose ratio of 0.28. A diagnosis of pyogenic meningoencephalitis was established. The patient made a complete recovery after a 14-day course of intravenous meropenem and vancomycin. MRI repeated 14 days after completion of antibiotics showed complete resolution of the splenial hyperintensity.