Collateral Circulation via the Ascending Pharyngeal Artery Arising from the Internal Carotid Artery
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* Akira Uchino

I read with interest the article by Chan et al.1 They stated that there was a rare *congenital* anastomosis between the vertebral artery (VA) and internal carotid artery (ICA) with an absence of communication between the common carotid and cervical ICA. I, however, diagnose that there was an *acquired* occlusion of the ICA at its origin with a development of collateral circulation from the VA to the ICA via the ascending pharyngeal artery.

I am very interested in the diagnosis of the cerebral arterial variations.2 It is well known that the ascending pharyngeal artery sometimes arises from the proximal ICA.3 In the patient reported by Chan et al, the ascending pharyngeal artery was well visualized, but opacification of the ICA was faint and delayed. This suggests that there was not a direct anastomosis between the VA and ICA.

In patients with congenital absence of the ICA, the common carotid artery and the proximal external carotid artery are usually the same size. In the patient reported by Chan et al, the common carotid artery was definitely larger than the proximal external carotid artery. This fact suggests that there was an acquired occlusion of the ICA at its origin.

## References

1.  Chan PN, Yu SCH, Boet R, et al. **A rare congenital anastomosis between the vertebral artery and internal carotid artery.** AJNR Am J Neuroradiol 2003;24:1885–86
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiYWpuciI7czo1OiJyZXNpZCI7czo5OiIyNC85LzE4ODUiO3M6NDoiYXRvbSI7czoyMToiL2FqbnIvMjcvMi8yNDYuMi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 

2.  Uchino A, Sawada A, Takase Y, et al. **MR angiography of anomalous branches of the internal carotid artery.** AJR Am J Roentgenol 2003;181:1409–14
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=14573446&link_type=MED&atom=%2Fajnr%2F27%2F2%2F246.2.atom) 

3.  Teal JS, Rumbaugh CL, Segall HD, et al. **Anomalous branches of the internal carotid artery.** Radiology 1973;106:567–73
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1148/106.3.567&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=4684800&link_type=MED&atom=%2Fajnr%2F27%2F2%2F246.2.atom) 
    
    [Web of Science](http://www.ajnr.org/lookup/external-ref?access_num=A1973O816500020&link_type=ISI) 

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*Reply:* 

We thank Dr Akira Uchino for his interest in our report and his thoughtful and reasoned letter. We have again examined our imaging findings and concluded that Dr Uchino’s observations are probably correct: 

1.  Complete occlusion of the internal carotid artery at its origin. The location of internal carotid artery origin matches well with the site of common carotid artery on angiography.

2.  There is no direct communication between vertebral artery and internal carotid artery. These vessels are connected by small collaterals, which likely arise from the ascending pharyngeal artery. This is in keeping with the slow flow in the internal carotid artery.

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