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Neuroradiology Case of the Week

Case 350

September 2008

Daniel Ginat, MD, MS and Sven Ekholm, MD, PhD

Clinical Presentation: Patient is a 68-year-old male with pneumonia and altered mental status.

Imaging Findings: Multiple foci of intracranial air in a venous distribution, including bilateral internal jugular veins, cavernous sinuses, and superficial soft tissues. No other significant abnormalities were encountered.

Diagnosis: Cerebral Venous Air Embolism

Discussion: The presence of air or gas within the cranial is an abnormal finding, termed pneumocephalus. CT is highly sensitive for detecting pneumocephalus, such that collections of air as small as 0.5mL can be discerned [1]. The most common etiologies of pneumocephalus are traumatic and iatrogenic. Air may also gain access to the intracranial space via cerebral arterial or venous embolism.
     Cerebral venous air embolisms, particularly small ones, are not uncommon, but are usually of no clinical significance. Reported symptoms attributed to venous air embolism are rare and self-limited [2]. The source of these emboli is from entry of air through peripheral and central intravenous lines. In patients that are upright or semi-upright, air bubbles are able to drift superiorly towards the slow flowing veins in the head and neck [3].
     The typical distribution of cerebral venous gas involves the cavernous sinus, the infratemporal fossa, the carotid canal, the straight sinus, the superior ophthalmic vein, the superior sagittal sinus, the region of the foramen magnum, jugular veins, and the inferior petrosal sinus [3]. Air may also be seen in the frontal and temporal scalp. Venous air usually dissipates to an undetectable level on CT within 48 hours [2].

References:

1. Harris JH, Harris WH. The Radiology of Emergency Medicine, 4th Ed., Lippincott Williams & Wilkins, New York, 2000.
   
2. Botez SA. Headache and cerebral venous air embolism. Neurology. 2007 Jan 2;68(1):19. [PubMed]
3. Rubinstein D, Dangleis K, Damiano TR. Venous air emboli identified on head and neck CT scans. J Comput Assist Tomogr. 1996 Jul-Aug;20(4):559-62. [PubMed]