Bing-Neel syndrome is a rare neurological complication of Waldenström macroglobulinemia. We present the case of a 71-year-old man who underwent prechemotherapy and postchemotherapy FDG PET/MRI scan for the evaluation of cerebrospinal disease. In light of limited literature and lack of consensus guidelines on the role of metabolic imaging, we aim to highlight the utility of FDG PET/MRI in the diagnosis and response assessment in Bing-Neel syndrome.