Late-onset encephalopathy usually has neurological damage that is irreversible. It does not usually heal on its own and may worsen further if not actively treated. Late-onset encephalopathy is caused by neurological damage, which mostly occurs in patients with carbon monoxide poisoning. It usually occurs in the recovery period of the disease within 2~60 days, with neurological as well as consciousness disorders, such as apathy, language impairment, memory loss, incontinence as well as extrapyramidal symptoms, etc., and it usually will not be cured on its own. If left untreated, late-onset encephalopathy not only does not resolve spontaneously, but may also cause permanent sequelae. Examples include motor aphasia, unresponsiveness, Parkinson’s syndrome, and seizures. When carbon monoxide poisoning occurs, early treatment, such as hyperbaric oxygen therapy, is necessary to prevent delayed encephalopathy. If delayed encephalopathy occurs, seek medical treatment promptly.