Cerebral Air Embolism Triggered by Infection of a Pulmonary Cyst in the Context of Air Travel: A Case Report.

Cerebral air embolism (CAE) is a rare and potentially fatal event. While most cases result from iatrogenic causes, such as central venous catheterization, pulmonary sources, especially infected cysts, are scarcely reported. We describe a case of a previously healthy 61‑year‑old man who lost consciousness immediately after a flight. On admission, his Glasgow Coma Scale was E3V1M3, and CT and MRI revealed multiple cerebral air emboli. He was intubated and treated with mechanical ventilation, targeted temperature management, and levetiracetam. CSF analysis showed no pleocytosis, and EEG revealed no epileptiform discharges. Follow-up CT and MRI demonstrated decreased pneumocephalus but manifestation of ischemic foci. Although consciousness improved to E4V4M6 and extubation was achieved, left hemiparesis persisted. Imaging on admission identified a 7-cm fluid-filled emphysematous lung cyst adjacent to the inferior pulmonary vein, accompanied by elevated inflammatory markers, which normalized after antibiotics; however, the cyst remained unchanged. Echocardiography and whole-body CT excluded cardiac shunts or vascular malformations. Notably, the patient reported a similar episode of confusion following a flight more than 10 years earlier, during which imaging was unremarkable, suggesting that a combination of factors, including a lung cyst and infection, as well as cabin pressure changes, may have played the triggering role in CAE. This report highlights that infection of a pulmonary cyst can result in systemic air embolism, particularly under barometric pressure fluctuations. Patients with known pulmonary cysts, especially frequent flyers, should undergo proactive evaluation and management of structural lung lesions to prevent air embolism.