symptomatic cerebral air embolism ( cae ) is a rare complication associated with cerebral angiography with a reported incidence of 0.08%.2 ) clinical manifestations of symptomatic cae may include decreased level of consciousness , hemiparesis , seizures , and neuromonitoring changes while under anesthesia.6 ) early recognition , diagnosis , and treatment of cae can minimize irreversible neurological deficits and avoid potential mortality .
we report on a rare case of cae , which highlights that symptomatic cae should be considered in differential diagnoses when abnormal neuromonitoring signals are observed during cerebral angiography and prompt treatment can minimize neurological deficits .
a 69-year - old female presented for elective stent - assisted coiling of a 7 mm , unruptured right middle cerebral artery ( mca ) bifurcation aneurysm .
she was started on aspirin 325 mg and clopidogrel 75 mg daily seven days prior to undergoing the elective procedure .
neuromonitoring with electroencephalography ( eeg ) and somatosensory evoked potential ( ssep ) were set up with good quality baseline signals prior to starting the procedure . a 6-french neuron guide catheter ( penumbra inc . ,
alameda , ca , usa ) was advanced over a 5-french berenstein catheter for selection of the patient 's right common carotid artery . using a roadmap technique and over - the - wire technique ,
the diagnostic catheter was used for selection of the patient 's right internal carotid artery .
a microcatheter ( excelsior sl-10 , stryker neurovascular , fremont , ca , usa ) and a wire ( synchro-14 , stryker neurovascular ) were then used for selective catheterization of the mca and coiling of the mca aneurysm was started . during coiling of the aneurysm however , the neurophysiologist reported severe attenuation of sseps in the bilateral upper and lower extremities along with near flatlining of the eeg .
there was no change in anesthetics , blood pressure , or body temperature prior to the ssep and eeg change .
an intraoperative dynact was then obtained and showed multiple , hypodense cortical vessels consistent with cerebral air embolism ( fig .
, it was noted that the pressure bag was depleted and a small amount of air was present in the drip line tubing .
the fio2 was increased to 100% on the ventilator , intravenous levetiracetam was administered , mean arterial blood pressure was increased , and intra - arterial verapamil infusion was administered in order to facilitate vasodilatation and to maximize cerebral perfusion .
the ssep and eeg signals showed gradual improvement approximately 30 minutes after the initial change .
given the patient 's improvement on neuromonitoring and risk of coil migration , an enterprise stent ( 4.5  22 mm ; cordis , bridgewater , nj , usa ) was deployed successfully across the aneurysm for completion of the procedure .
the catheter was retracted out of the body . a 6-french angio - seal closure device ( st . jude medical , st .
magnetic resonance imaging ( mri ) of the brain showed only a small focal area with restricted diffusion in the right parietal region ( fig .
the patient 's left hemiparesis showed gradual improvement over the next few days and she was eventually discharged with near baseline strength .
follow - up angiogram at four weeks showed raymond grade 1 occlusion of the right mca aneurysm ( fig .
cerebral air embolism is known to occur in a number of clinical settings , including cranial surgeries in the sitting position , trauma , decompression sickness , and cardiopulmonary bypass procedures.6 ) in many of these situations , air first enters into the venous circulation and subsequently migrates to the arterial side from either a patent foramen ovale or other cardiopulmonary shunts ( paradoxical embolism ) . during cerebral angiography ,
however , air can be introduced directly into the arterial circulation and therefore is more likely to cause neurological symptoms .
fortunately , the overall incidence of symptomatic cae associated with cerebral angiography is extremely low . in a study examining more than 4,500 cerebral angiographies , only four cases of symptomatic cae
of particular interest , all four cases of cae occurred during interventional cases and conferred a risk of 0.2%.2 ) several sources for air emboli in the setting of cerebral angiography have been reported in the literature , including air bubbles in the flush syringe , air bubbles in improperly primed flush tubing , non - degassed pressure bag , accidentally opened 3-way stopcock during an episode of hypotension , and rupture of an inadequately degassed angioplasty balloon.2)4 ) in our case , air was introduced from the pressure bag , which had been inadequately degassed prior to the procedure ; when the pressure bag was depleted , the small amount of residual air in the bag subsequently moved into the drip line , the guide wire , and eventually into the cerebral vasculatures .
when cae is suspected during cerebral angiography , a quick angiogram can be helpful in assessment for any large vessel occlusion .
computed tomography ( ct ) or dynact , if available , is a quick way to look for intracranial air , which can often demonstrate the outline of affected cerebral vasculature as the air emboli serve as a negative contrast medium .
mri can also demonstrate intracranial air as hypointensity on t1-weighted sequence , however , the time requirement and patient transport often limit its role in acute diagnosis of cae ; however , mri is valuable in assessing the extent of ischemic changes due to cae .
once the diagnosis of cae has been established , several measures can be taken to minimize potential neurological deficits . first , 100% o2 can be used to dilute nitrogen in the air emboli ( same composition as the earth 's atmosphere , ~ 78% n2 and 21% o2 ) and facilitate absorption of air .
second , mean arterial pressure can be raised to increase cerebral blood flow , which helps to increase perfusion of the affected area from collateral vessels and to increase the rate of air absorption .
third , as in our case , intra - arterial verapamil infusion can potentially increase cerebral vessel dilation to maximize cerebral perfusion and to facilitate more distal migration of air emboli .
another important treatment option for cae is placing the patient in a hyperbaric chamber , where increased pressure can decrease air emboli size and increase the amount of gas molecules dissolved in the blood stream .
however , the utilization of hyperbaric chambers is limited by availability . finally , early prophylactic anticonvulsants should also be considered , given that many patients with cae are prone to having seizures .
prevention of cae is paramount in every neurointerventional case and all potential sources for introduction of air into the drip line should be checked carefully prior to starting any procedure .
the prognosis of cae depends on a combination of several factors , including the amount of air present , collateral circulation , time of diagnosis , time of intervention , and treatment strategies utilized .
many patients with cae can have complete recovery ; however , permanent neurological injuries and mortality can also occur if diagnosis and proper intervention is delayed.1)2)3)4)5)6 )
symptomatic cerebral air embolism is a rare but important complication associated with cerebral angiography which all neurointerventional surgeons should bear in mind . with prompt
diagnosis and appropriate management , major permanent neurological deficits and mortality can often be avoided .
 symptomatic cerebral air embolism during cerebral angiography is extremely rare . 
 we report on the case of a 69-year - old woman undergoing elective stent - assisted coiling of an unruptured right middle cerebral artery ( mca ) bifurcation aneurysm , who was found to have severe attenuation of somatosensory evoked potential ( ssep ) and electroencephalography ( eeg ) during the procedure . 
 intra - operative dynact showed hypodense cortical vessels consistent with cerebral air embolism . 
 diagnostic and management strategies for this rare complication are reviewed . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION