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Whole Brain CT Perfusion after Cerebral Air Embolism

Cerebral air embolism (CAE) occurs as a result of air entering the arterial or venous circulation. Iatrogenic causes of CAE are found across all specialties, and include inadvertent air entry during cardiac catheterization, angiography, lung biopsy or via an intravascular catheter1,2. Ischemic brain injury occurs when air emboli directly obstruct intracranial arteries or cause inflammation, blood brain barrier breakdown and cerebral edema which secondarily interfere with blood supply to the brain1,2. Patients with CAE develop sudden neurological symptoms which vary based on the absolute volume of air introduced and extent of brain affected. Symptoms are non-specific and range from confusion or disorientation to coma, seizures or focal deficits such as hemiparesis1. A high index of suspicion is required when neurological symptoms develop in temporal association with surgical or invasive procedures that carry a risk of air embolism3. Consideration of a diagnosis of CAE may be delayed or masked in patients that have received general anesthesia or conscious sedation1. Neuro-imaging can be helpful in establishing a diagnosis of CAE.Air emboli may be directly demonstrated by non-enhanced computed tomography (NECT), however, microscopic CAE or small volumes of intravascular air may be missed. Air is rapidly absorbed from the cerebral circulation and thus delays in acquiring brain imaging may result in false negative computed tomography (CT) scans4. The use of magnetic resonance imaging (MRI) is limited by the time delay in obtaining imaging and lengthy scan times both of which are undesirable in potentially unstable patients. A rapid imaging method that can accurately demonstrate CAE would thus be of use. We report two cases of cerebral air embolism evaluated acutely using an imaging protocol consisting of NECT of the head, computed tomogram angiography (CTA) of the head and neck and whole brain CT perfusion (CTP). To the best of our knowledge, this is the first report of CTP use in the acute evaluation of suspected CAE.