European Radiology

, Volume 23, Issue 6, pp 1478–1486

Calcium at the carotid siphon as an indicator of internal carotid artery stenosis

  • Nikola Gotovac
  • Ivana Išgum
  • Max A. Viergever
  • Geert J. Biessels
  • Josip Fajdić
  • Birgitta K. Velthuis
  • Mathias Prokop

DOI: 10.1007/s00330-012-2766-x

Cite this article as:
Gotovac, N., Išgum, I., Viergever, M.A. et al. Eur Radiol (2013) 23: 1478. doi:10.1007/s00330-012-2766-x



Carotid siphon calcification is often visible on unenhanced head CT (UCT), but the relation to proximal carotid artery stenosis (CAS) is unclear. We investigated the association of carotid siphon calcification with the presence of CAS.


This IRB-waived retrospective study included 160 consecutive patients suspected of stroke (age 64 ± 14 years, 63 female) who underwent head UCT and CTA of the head and neck. CAS was rated on CTA as not present or present with non-significant (<50 %), moderate (50–69 %) or significant (≥70 %) stenosis. Presence, shape (on UCT) and volume (on CTA) of carotid siphon calcifications were related to CAS.


Carotid siphon calcification was absent in 41 % of patients and bilateral in 94 % of those with calcifications. Presence, shape and volume of calcification resulted in odds ratios for having significant CAS of 10.1, 3.9 and 8.4, with 95 % CIs of 1.3–79.6, 1.1–14.1 and 2.6–26.8, respectively. Corresponding NPVs were 0.98, 0.98 and 0.96, while PPVs were 0.14, 0.07 and 0.29, respectively.


Absence of calcification in the carotid artery siphon on UCT has high negative predictive value for carotid artery stenosis in patients with suspected stroke. However, siphon calcification is not a reliable indicator of significant carotid artery stenosis.

Key Points

Many stroke patients do not have calcification in the carotid artery siphon.

Carotid stenosis50 % is unlikely in stroke patients without siphon calcification.

Carotid siphon calcium is a poor indicator of significant carotid artery stenosis.


Atherosclerosis Intracranial atherosclerosis Internal carotid artery Vascular calcification Carotid stenosis 



Proximal internal carotid artery stenosis


95 % confidence interval


Computed tomography


Computed tomography angiography


Unenhanced computed tomography


Hounsfield units


Positive predictive value


Negative predictive value


Transitory ischaemic attack

Copyright information

© European Society of Radiology 2013

Authors and Affiliations

  • Nikola Gotovac
    • 1
    • 2
  • Ivana Išgum
    • 2
  • Max A. Viergever
    • 2
  • Geert J. Biessels
    • 3
  • Josip Fajdić
    • 4
  • Birgitta K. Velthuis
    • 5
  • Mathias Prokop
    • 5
    • 6
  1. 1.Department of RadiologyCounty hospital PožegaPožegaCroatia
  2. 2.Image Sciences InstituteUniversity Medical Center UtrechtUtrechtThe Netherlands
  3. 3.Department of Neurology, Rudolf Magnus Institute of NeuroscienceUniversity Medical Center UtrechtUtrechtThe Netherlands
  4. 4.Department of SurgeryCounty hospital PožegaPožegaCroatia
  5. 5.Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
  6. 6.Department of RadiologyRadboud University Nijmegen Medical CentreNijmegenThe Netherlands

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