Suspected Acute Disseminated Encephalomyelitis Presenting With Persistent Vegetative State and Full Neurological Recovery in an Adult: A Case Study.

Acute disseminated encephalomyelitis (ADEM) is an autoimmune inflammatory disease of the central nervous system that typically presents with headache, fever, altered consciousness, and seizures. Diagnosis is made clinically and radiologically, supported by the exclusion of mimics. Delayed treatment can lead to severe neurological impairment, including a persistent vegetative state. A 69-year-old Asian female with rheumatic heart disease and prior transverse myelitis presented with hypoxic respiratory failure. On hospital day (HD) 4, she developed a rapid decline in mental status, progressing to a vegetative state with electroclinical seizures. Brain MRI showed diffuse, symmetric T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities involving subcortical white matter, which is an atypical finding for classic ADEM. Extensive infectious and autoimmune testing was unrevealing. Lumbar puncture on HD 11 (prior to steroids) showed no pleocytosis. She remained vegetative for 39 days without response to high-dose corticosteroids. Following a five-day course of intravenous immunoglobulin (IVIG), she showed marked neurological recovery. At discharge, she returned to her baseline functional status. This case illustrates the diagnostic challenges of suspected ADEM in an older adult with atypical symmetric imaging, prolonged vegetative state, and delayed response to immunotherapy. The case adds to the limited literature on extended encephalopathy in suspected ADEM and underscores the role of IVIG when steroid response is unclear.