Anastamoses between internal and external carotid arteries

Last revised by Daniel J Bell on 3 May 2022

Multiple, highly-variable anastomoses exist between the internal and external carotid arteries. These anastomoses may not be evident on non-invasive imaging or even catheter angiography, and may only be demonstrable with elevated intra-arterial pressures or high-flow states.

Internal carotid artery - external carotid artery (ICA-ECA) collaterals may enlarge following occlusion of the ICA and have been implicated in the development of dural arteriovenous fistulas (dAVF).

A non-exhaustive list of such sites includes:

Collateral pathways are also present between the occipital artery (from the ECA) and muscular branches of the vertebral arteries around the C1 and C2 vertebrae 1.

See also

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