Cerebral gas embolism resulting from inhalation of pressurized helium

Loss of consciousness, a generalized tonic-clonic seizure, rightside weakness, and pneumomediastinum developed suddenly in a 13-year-old boy who had inhaled helium directly from a pressurized helium tank. His condition improved dramatically with hyperbaric oxygen treatment, and he had apparently regained complete neurologic function by the time of follow-up 2 weeks later. On the basis of the boy's clinical presentation and his response to hyperbaric oxygen therapy, we diagnosed a cerebral gas embolism.