A 72-year-old female presented to the hospital with acute mental status changes and a 1-week history of periorbital eye and neck swelling. She had a medical history of stage 3 multiple myeloma considered in remission post stem cell transplant and advanced-stage suspected Lewy body dementia. Following admission, she was found to have bilateral optic disc edema, acute E. coli urinary tract infection, and possible normal pressure hydrocephalus. Laboratory findings in her cerebrospinal fluid (CSF) included increased white blood cells, increased red blood cells, and increased total protein. These results were consistent with meningoencephalitis. Antibiotics were given to control the urinary tract infection and meningoencephalitis and were discontinued after CSF culture was found negative. Given her past medical history of multiple myeloma, there was also concern for neoplastic meningoencephalitis related to recurrent myelomatous involvement of the central nervous system (CNS). Therefore, serum free light chains (FLCs), serum, urine, and CSF protein electrophoresis, CSF cytology, and flow cytometry studies were ordered.