barotrauma - induced pneumocephalus resulting from a rapid change in the surrounding pressure is a major concern for airline passengers and scuba divers5,6,9 - 11,14 ) . recent advances in aircraft technology have led to a tremendous increase in air travel for the general population and for neurosurgical patients . neurosurgical procedures , including cranial and spinal surgery , could be a cause of residual intracranial air and could create a dormant fistulous tract that opens when the cabin pressure changes . during air travel , a neurosurgical patient could experience fatal tension pneumocephalus resulting from expansion of residual air in the head and pneumoencephalomeningitis secondary to cerebrospinal fluid ( csf ) leakage and the backflow of contaminated air through the bony defect . to generate interest and considerations about safe air travel of neurosurgical patient among practicing consultant neurosurgeons , the authors report a rare case of barotrauma - induced pneumocephalus experienced by a high risk patient after commercial air travel . a 49-year - old female presented to the emergency department with a severe headache , nausea , and vomiting after one hour flight on a domestic commercial airliner . a cranial nerve examination revealed anosmia through both nostrils and a visual field defect of the left inferior homonymous quadranopsia . additional cranial nerve function , motor and sensory function , the deep tendon reflex , and cerebellar function were normal . ten years ago , this patient was diagnosed with meningioma in the occipital lobe and underwent a suboccipital craniotomy to remove the tumor at another hospital . further questioning revealed that the patient underwent four additional otolaryngologic operations ( two operations involving the mastoid sinus and two involving the frontal skull base through the nose ) to manage csf rhinorrhea four years after initial the craniotomy . finally , a lumboperitoneal shunt was placed , and the patient did not experience further symptoms of a csf leak . the revision surgery for a recurrent tumor was performed last year ; at the time of the incident discussed here , the patient was returning home after gamma knife radiosurgery for the residual tumor . 1 ) demonstrated extensive air within the subarachnoid space of the basal cistern , bilateral lateral and third ventricle , and extending to the intraparenchymal portion of the left frontal lobe . the routine laboratory blood tests ( leukocyte count , hemoglobin , hematocrit , glucose , blood urea nitrogen , creatinine , sodium , potassium , chloride , and c - reactive protein ) were normal . normal saline and analgesics were administered via an intravenous line , and a gradual resolution of the headache was achieved within several days . seven days after presentation , the patient reported no complaints , and no evidence of meningoencephalitis was observed . the patient was warned not to fly before a definite diagnostic work up and sealing procedure for the csf leak site was performed , and the patient was then discharged . the second world war led to tremendous advances in the technologies related to airplanes and enabled many people to travel by air . although modern commercial aircrafts provide safe and comfortable travel for most healthy people , the in - flight environment consisting of a lowered barometric pressure , ambient oxygen partial pressure , and low humidity1 ) could expose a high risk patient ( such as the patient discussed here ) to danger . international jet airliners fly at an altitude of 9750 to 11580 meters ( 32000 to 38000 feet ) , and domestic airlines fly at 8530 to 8840 meters ( 28000 to 29000 feet ) . modern jet aircrafts are not pressurized to a sea level equivalent pressure ( 760 mm hg ) . during flight , the cabin is pressurized to maintain the pressure equivalent to the altitude of 1520 to 2440 meters ( 5000 to 8000 feet)1 ) . in other words , the cabin pressure is maintained within 536 to 611 mm hg . gas in the cabin has been shown to expand its volume by 25 - 30% during flights3 ) . neurosurgical , plastic , and otolaryngologic procedures , especially a craniotomy or skull base surgery , could leave air in the skull and create weak areas where a csf leak could occur . the traveling patient could potentially encounter two neurosurgical problems : tension pneumocephalus resulting from expansion of the residual air after a craniotomy or a csf leak through a bony defect made by surgical procedures , resulting in pneumocephalus or pneumomeningoencephalitis . until now , there have not been any reported cases of tension pneumocephalus caused by residual air during flight . donovan et al.7 ) reported no aggravated cases of neurological deficits and intracranial pressure among twenty - one military casualties with pneumocephalus caused by trauma or a craniotomy during air transport from iraq to germany under usual cabin pressure . two british studies focused on the medical advice given to post - craniotomy patients regarding air travel and addressed the unstandardized approach of airline companies and insufficient consensus among practicing consultant neurosurgeons2,13 ) . a cracked tooth5 ) , mastoid air cells10 ) , osteoma of the skull base11 ) , pansinusitis6,9 ) , and a fistulous tract made by cranial4 ) and spinal8 ) surgery were suggested as weak areas or causes of weak areas that were susceptible to pressure changes . in our case , pneumocephalus appeared to occur through the dormant fistulous tract because of the lowered cabin pressure and the synergistic effect of the lumboperitoneal shunt . the medical guideline recommends waiting at least 7 days to fly after a transcranial procedure or a trauma that introduced gas into the skull without reliable evidence from a plain skull radiograph or ct scan that no air is present . moreover , a person with a csf leak from any cause should not fly due to the risk of a backflow of air and microbial contamination1 ) . although it is difficult to make one guideline to apply to all cases , the concern for possible problems during air travel by patients could lead to consensus among practicing consultant neurosurgeons . creating guidelines for safe air travel for patients with neurosurgical problems is an important issue to consider because of the frequency with which some patients travel . a consultation with a health care provider addressing the cabin environment and neurosurgical conditions could be helpful for these patients .