String sign (artery)

Last revised by Joshua Yap on 2 Mar 2023

The angiographic string sign, also known as the carotid string sign or slim sign, refers to the thin string of intravascular contrast material distal to a stenotic focus in the internal carotid artery (ICA)


A thin stripe of flow is caused by decreased pressure and flow distal to the stenosis, which causes a collapse of the distal ICA.


An angiographic string sign may be caused by:

  • pre-occlusive atherosclerosis at the carotid bifurcation

  • ICA dissection

  • ICA thrombosis

    • subacute partial

    • chronic subtotal

  • partial recanalization of an occluded ICA

  • stenosis secondary to radiation

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Cases and figures

  • Case 1: ICA string sign
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