The presentation of a transient hyperintense lesion with Legionnaires disease in a patient--is it a coincidence or an incidental finding?

Up to date the presentation of transient splenial lesions in corpus callosum were reported in diffusion weighted magnetic resonance imaging (MRI) only in epileptic patients and patients under antiepileptic therapy. A 41 year old male with no previous medical history was admitted to our clinic with symptoms of pneumonia. The neurological exam revealed stupor, but when awake his speech and orientation were normal. There were no meningeal irritation signs, cranial nerves, piramidal and cerebellar functions were normal. He had moderate respiratory distress and had bilateral rales in lower lobes while on auscultation. Laboratory tests revealed high liver function levels and high acute phase reactants. Arterial blood levels showed hypoxemia. A brain MRI showed a hypointensity in the splenium of corpus callosum on T1 weighted images. There was markedly increased signal in this region on diffusion weighted imaging and hypointense on ADC. The lesion was slightly hyperintense on T2 and FLAIR weighted images. A repeat brain MRI was done 30 days after the initial study and showed a complete resolution of the splenial lesion. Transient splenial lesions can be seen due to different mechanisms in different clinical settings. It should be noted that these lesions are mostly reversible. Unnecessary therapies and procedures should be avoided in these lesions.