Incidence, radiographical features, and proposed mechanism for pneumocephalus from intravenous injection of air

Abstract

Background: Pneumocephalus typically implies a traumatic breach in the meningeal layer or an intracranial gas-producing infection. Unexplained pneumocephalus on a head computed tomography (CT) in an emergency setting often compels emergency physicians to undertake aggressive evaluation and consultation.

Methods: In this paper, we report three cases of pneumocephalus that appear to result from retrograde injection of air through an intravenous (IV) catheter. We also performed a retrospective study to determine the incidence of presumed IV-induced pneumocephalus and etiologies of pneumocephalus in our emergency department (ED) population.

Results: The incidence of idiopathic and presumed IV-induced pneumocephalus was 0.034% among all head CTs ordered in the ED and 4.88% among cases of pneumocephalus seen in the ED. These cases are characterized clinically by the absence of signs and symptoms of pathologic pneumocephalus and radiographically by the distribution of air densities along the cranial venous system on head CTs.

Conclusion: Idiopathic and presumed IV-induced pneumocephalus could be considered in the workup of ED patients with unexplained intracranial air on head CT if there are no findings of pathological causes for the pneumocephalus on history and physical examination and if the head CTs show a characteristic distribution of air limited to the cranial venous system. Knowledge of this clinical entity in the evaluation of ED patients with unexplained pneumocephalus can lead to more efficient emergency care and less patient anxiety.

Figure 1.

(Case 1). Axial cranial computed tomography through the sella region of a 55-year-old female who presented to the emergency department with the chief complaint of frontal headache. Air in the right cavernous sinus (white arrow heads, A and B), right superficial temporal veins (arrow, A), and left intraorbital veins (black arrow head, B).

Figure 2.

(Case 2). Axial cranial computed tomography through multiple levels in an 87-year-old female who presented to the emergency department with the chief complaint of altered mental status. Air is seen in the in the right cavernous sinus (white arrow heads, B), right superior orbital veins (black arrow head, A) and right superficial temporal veins (arrow, B).

Figure 3.

(Case 3). Axial cranial computed tomography through the sella region of an 56-year-old male who presented to the emergency department with the chief complaint of fall after feeling a loss of control of his body. Air is seen in bilateral cavernous sinus (white arrowheads, A), behind the dorsum sella (black arrowheads, A), and right superficial temporal veins (arrow, B).

Figure 4.

“Mount Fuji” sign. Axial cranial computed tomography through the level of frontal horns shows a large subdural bilateral pneumocephalus post-operatively. Note the compression of the frontal lobes and widening of the interhemispheric space between the frontal lobes, simulating the appearance of Mount Fuji.

Figure 5.

Axial (A), coronal (B) and sagittal (C) computed tomography reformatted views of soft tissue of the neck, showing contrast flow cephalad into the left internal (white arrowheads) and external jugular veins (black arrowheads) during a left upper extremity contrast injection for a head and neck computed tomography angiogram (white arrowheads: internal jugular, black arrowheads: external jugular).