Resection of superior sulcus neoplasms is associated with a number of complications resulting from the extensive nature of the resection and the necessity to sacrifice certain adjacent structures. One of the complications of resection is the development of subarachnoid-pleural fistula, with the subsequent appearance of air in the cerebrospinal fluid circulation. We report a case in which a subarachnoid-pleural fistula led to persistent pneumocephaly in a patient who exhibited postoperative hyponatremia, confusion, and gait disturbance.