We report a case of intracranial hypotension (IH) after thoracotomy. A 56-year-old woman presented 10 days after a left upper lobectomy with severe headache due to pneumocephalus and pneumorrhachis, which resolved on conservative treatment. Two months later, the patient was readmitted in an unconscious state with characteristics of IH and "sagging brain." Subsequent magnetic resonance imaging revealed a fistula at the level of the left Th5 pedicle. The patient underwent operation with closure of the fistula and recovered without complications. The presence of pneumocephalus and pneumorrhachis after thoracotomy should raise the suspicion of a persistent subarachnoid-pleural fistula to prevent IH and "sagging brain." (C) 2020 by The Society of Thoracic Surgeons