Which option correctly lists the three arterial collateral pathways in the brain when the right internal carotid artery is occluded?

Which option correctly lists the three arterial collateral pathways in the brain when the right internal carotid artery is occluded?

• A. Ipsilateral external to internal via orbital arteries
• B. Posterior to anterior via the PCA
• C. Side-to-side crossover via the ACA
• D. Side-to-side crossover via ACA, Posterior to anterior via PCA, and Ipsilateral external to internal via orbital arteries

Answer: (D)

When the right internal carotid artery is occluded, the brain relies on collateral routes to maintain perfusion to the territory normally supplied by the ICA. The three main pathways are: one, ipsilateral external carotid to internal carotid connections via orbital/ophthalmic arteries, providing local collateral flow to the ICA territory on the same side; two, cross-flow between the two anterior cerebral arteries through the anterior communicating artery, allowing blood from the opposite ICA to reach the affected side; and three, posterior-to-anterior flow through the posterior communicating arteries linking the posterior circulation (via the posterior cerebral arteries) to the internal carotid/ anterior circulation. Together these three pathways account for collateral circulation when the right ICA is occluded, which is why the option listing all three is correct.

When the right internal carotid artery is occluded, the brain relies on collateral routes to maintain perfusion to the territory normally supplied by the ICA. The three main pathways are: one, ipsilateral external carotid to internal carotid connections via orbital/ophthalmic arteries, providing local collateral flow to the ICA territory on the same side; two, cross-flow between the two anterior cerebral arteries through the anterior communicating artery, allowing blood from the opposite ICA to reach the affected side; and three, posterior-to-anterior flow through the posterior communicating arteries linking the posterior circulation (via the posterior cerebral arteries) to the internal carotid/ anterior circulation. Together these three pathways account for collateral circulation when the right ICA is occluded, which is why the option listing all three is correct.