CASE 18518 Published on 08.04.2024

Spontaneous hypodense appearance of the cerebral venous sinuses in anaemic patient



Case Type

Clinical Case


Jan Lievens, Davy Christiaens, Bart Claikens

AZ Oostende, Ostend, Belgium


71 years, male

Area of Interest Neuroradiology brain ; Imaging Technique CT
Clinical History

A 71-year-old man, who is actively undergoing chemotherapy for a piriform sinus carcinoma, presented with generalised weakness, dizziness and vertigo when standing up, followed by brief syncope. Clinical examination revealed blood pressure of 89/47 mmHg, tachycardia of 100 bpm and dyspnoea. Blood test demonstrated haemoglobin level of just 59 g/l (135–175 g/l) and a haematocrit of 17.3% (41–53%).

Imaging Findings

A non-enhanced CT scan of the brain was performed and revealed a strikingly homogeneously hypodense superior sagittal sinus, transverse sinus bilaterally, as well as basilar artery, especially when compared to imaging performed 2 years prior (Figures 1 and 2).

The mean density measured in the superior sagittal sinus was around 35 HU compared to a prior CT scan in which the density was around 62 HU.

The cerebral venous sinus did not appear dilated and there was no brain oedema to be withheld.

No further relevant findings were visualised in the CT.

Additionally, a contrast-enhanced CT was performed in order to exclude a dural venous sinus thrombosis, which was negative, as shown in Figure 3.


Anaemia is characterised by the presence of reduced haemoglobin in the blood. The WHO defines anaemia as a haemoglobin level <130 g/l for adult men and <120 g/l for adult women.

Clinically this usually presents as generalised fatigue or weakness. Severe cases may present as shortness of breath, reduced exercise tolerance and even syncope [1]. A simple blood test can easily objectivate these symptoms as a result of anaemia.

Haemoglobin also plays a major role in how dense blood appears on CT scan. It is mainly haemoglobin that causes blood to be dense on CT, more specifically the protein fraction of haemoglobin, as the contribution of the iron atom itself is minimal [2]. During bleeding, water content decreases, and consequently, the concentration of haemoglobin rises up to 90%, resulting in an increased attenuation of fresh blood clots. Also in polycythaemia vera, blood becomes more dense on CT caused by an increased haemoglobin level. Conversely, therefore, when the haemoglobin content of the blood decreases, the density of the blood also decreases as illustrated in this reported case [3]. Attenuation measurements of less than 35 HU in the superior sagittal sinus detect anaemia with a specificity of 100% [4]. Anaemia can also be suggested on unenhanced thorax CT when the interventricular septum is visualised [5].

The most important pathologies to rule out during a non-contrast CT scan of the brain in an emergency setting are acute brain haemorrhage or thrombosis in either an intracranial artery or the cerebral venous sinus. Both acute haemorrhage and thrombosis typically appear as hyperdense entities on CT. As a result, radiologists are aware of the critical importance of recognising hyperdensity of blood and/or vessels during a non-contrast brain CT in the emergency setting. Consequently, the often more subtle finding of hypodense blood is probably underreported. It should be noted, however, that there has been a reported case of cerebral venous sinus thrombosis appearing hypodense on non-contrast CT, demonstrating that excluding the hyperdense appearance of these structures may very rarely not suffice to exclude venous cerebral sinus thrombosis. The hypodense appearance of the thrombus was accredited to the thrombus being of a more subacute nature (6–15 days old) rather than acute, as is more often the case [6].

Given the amount of CT scans that are performed without lab results this rapid assessment technique can be useful for narrowing possible diagnoses.

Written informed patient consent for publication has been obtained.

Differential Diagnosis List
Chemotherapy-induced normocytic anaemia
Venous sinus thrombosis
Final Diagnosis
Chemotherapy-induced normocytic anaemia
Case information
DOI: 10.35100/eurorad/case.18518
ISSN: 1563-4086