The brain receives oxygenated blood from both the internal carotid arteries and the vertebral arteries, which are connected through the Willis circle (Circulus arteriosus cerebri).

enter image description here

Obstruction of terminal vessels such as the A. cerebri media obviously leads to neurological symptoms, but is the Willis circle able to compensate the unilateral total occlusion of any of the 4 main sources of oxygen to the brain?

1 Answer 1


Unilateral carotid compression (Carotid Compression Test) is an important procedure before performing vascular surgery for either of the carotid arteries, because during the surgery, they need to be compressed upstream for obvious reasons.

Numbers vary, but in 6%1 to 26%2 of patients, the compensation through the circle of willis was insufficient:

Forty five patients showed no changes during the carotid compression. Two cases showed both weakness of the contralateral side and altered consciousness within 10 seconds of compression. A third patient developed profound altered consciousness with no discernable lateralizing signs. In all 3 cases, these findings were completely reversed within 5 seconds of release of digital compression.

1: Naraynsingh V, Harnarayan P, Maharaj R, Dan D, Hariharan S. Preoperative digital carotid compression as a predictor of the need for shunting during carotid endarterectomy. Open Cardiovasc Med J. 2013;7:110-112. Published 2013 Nov 15. doi:10.2174/1874192401307010110

2: Hetzel A, von Reutern G, Wernz MG, Droste DW, Schumacher M. The carotid compression test for therapeutic occlusion of the internal carotid artery. Comparison of angiography with transcranial Doppler sonography. Cerebrovasc Dis. 2000;10(3):194-199. doi:10.1159/000016056

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.