Successful treatment of an older patient with delayed neurological sequelae and delirium after carbon monoxide poisoning with memantine

Carbon monoxide (CO) poisoning can cause delayed neurological sequelae (DNS), a condition with no effective treatment. We report a 66-year-old male patient who recovered from acute CO poisoning but developed DNS and delirium one week later. He showed akinetic mutism, parkinsonism, rigidity, and cognitive impairment. Non-pharmacological approaches and donepezil were tried, but due to side effects, memantine (20 mg/day) was started. Over the course of one year, the patient showed significant improvement in neurological and functional status, with improvements in cognitive function (Mini-Mental State Examination: 26) and brain magnetic resonance imaging findings. This case suggests memantine may contribute to DNS recovery.