What is the normal diameter of the internal carotid artery (ICA)?

What is the normal diameter of the internal carotid artery (ICA)?

• A. 3-4 mm
• B. 4-5 mm
• C. 2-3 mm
• D. 5-6 mm

Answer: (B)

The diameter of the internal carotid artery in a healthy adult is typically about 4 to 5 mm. This range is what clinicians use as the standard reference because the ICA is a large, high-flow vessel and its size remains fairly consistent along the cervical segment in normal conditions. Measurements can vary slightly with technique, patient anatomy, and imaging level, but 4–5 mm is the most commonly cited normal range. If the vessel were significantly smaller, like 2–3 mm, that would raise concern for stenosis or a congenitally small artery; if it were larger, such as 5–6 mm, it could reflect measurement variation or high-flow states but is less representative of the typical norm. Hence, 4–5 mm is the best answer.

The diameter of the internal carotid artery in a healthy adult is typically about 4 to 5 mm. This range is what clinicians use as the standard reference because the ICA is a large, high-flow vessel and its size remains fairly consistent along the cervical segment in normal conditions. Measurements can vary slightly with technique, patient anatomy, and imaging level, but 4–5 mm is the most commonly cited normal range. If the vessel were significantly smaller, like 2–3 mm, that would raise concern for stenosis or a congenitally small artery; if it were larger, such as 5–6 mm, it could reflect measurement variation or high-flow states but is less representative of the typical norm. Hence, 4–5 mm is the best answer.