First AD

Second AD

A 33-year-old male with history of cyanotic congenital heart disease status post multiple palliative cardiac surgeries, atrial fibrillation on warfarin, presents with altered mental status.

Normal enhanced CT examination of the head


There is no acute intracranial hemorrhage, acute infarct, or other acute abnormality. The intracranial vasculature appears hyperdense due to increased hematocrit.

Chronic hypoxemia secondary to right-to-left shunting in this patient with cyanotic congenital heart disease results in compensatory increased hematocrit. This patient had a hematocrit of 66% (normal 40%-52%).


On an unenhanced CT examination of the head, normal flowing blood within the intracranial arteries are approximately 40 Hounsfield units (HU). Increased hematocrit, whether diffuse or focal, such as in thrombus, results in increased intraluminal attenuation (approximately 80 HU). This is the basis of the “hyperdense vessel” sign due to intraluminal thrombus, where extrusion of serum and clot retraction results in focal intraluminal hyperattenuation. This may also be seen in the venous sinuses with venous sinus thrombosis. Care must be taken to differentiate the hyperdense vessel sign from intracranial atherosclerotic calcification.

Overall increased hematocrit results in diffusely increased density of the vessels due to hemoconcentration. In this patient, increased hematocrit is a compensatory mechanism for chronic hypoxemia due to the patient’s right-to-left shunt cardiac physiology. Diffuse hyperattenuation of the vessels may mimic a contrast-enhanced CT examination, such as in this exam.

Another mimic of hyperdense vessels is diffuse cerebral edema resulting in relatively low density of the brain parenchyma compared to the vasculature.


Black DF, Rad AE, Gray LA, Campeau NG, Kallmes DF. Cerebral venous sinus density on noncontrast correlates with hematocrit. 

Ledezma CJ, Wintermark M. Multimodal CT in stroke imaging: new concepts.

Mullins ME. The hyperdense cerebral artery sign on head CT scan. 

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33-year-old male with history of cyanotic congenital heart disease status post multiple palliative cardiac surgeries.

Image IQ: History of Cyanotic Congenital Heart Disease

Geraldine Liao, MD