Acute cognitive disorder as the initial manifestation of nitrous oxide abusing: a case report.

Nitrous oxide (N2O) is a colorless, odorless gas used as an anesthetic and analgesic. It is also abused as a recreational drug, and such abuse is associated with neurological disorders and psychiatric complications such as myelopathy and, rarely, cognitive impairment. Its abuse has not been associated with acute cognitive decline. Here, we report a young girl who presented with acute cognitive impairment after excessive recreational inhalation of nitrous oxide and who recovered completely after vitamin B12 supplementation. We conclude that nitrous oxide abuse can cause acute cognitive impairment, and that this diagnosis should be considered if a patient initially presents with acute cognitive decline.