A case of enteroviral meningoencephalitis presenting as rapidly progressive dementia

Background A 70-year-old immunocompetent male presented to a memory disorders clinic with a 7-month illness that had begun with somatic complaints including transient right temporal head pain, left buttock pain, and right conjunctival injection. About 3 months after the first signs of illness, the patient had begun to develop insidious cognitive and behavioral decline, which progressed most rapidly in the 2 months before presentation. An assessment completed during hospitalization for intermittent fevers and confusion had not revealed an infectious etiology, although mild pleocytosis in the cerebrospinal fluid had been noted. Upon presentation to the memory disorders clinic, the patient was disoriented, distractible, laughed at inappropriate moments, and followed only one-step commands. He had hypophonic speech and had mildly increased axial tone. He scored 5 out of 30 on the Mini Mental State Examination and was admitted for expedited evaluation. Investigations Physical examination, brain MRI, electroencephalogram, lumbar puncture, autoimmune and paraneoplastic testing, cerebral angiogram, cerebrospinal fluid analysis, enterovirus group-specific reverse transcriptase polymerase chain reaction assay, and RNA sequencing in brain biopsy samples. Diagnosis Enteroviral meningoencephalitis. Management Intravenous steroids with oral taper and intravenous immunoglobulin.