In transtemporal Doppler, which vessel at 60-80 mm depth demonstrates retrograde flow with velocity near 55 cm/s?

• A. Middle cerebral artery
• B. Anterior cerebral artery
• C. Posterior cerebral artery
• D. Terminal internal carotid artery

Answer: (B)

In transtemporal Doppler, you identify vessels by where they sit beneath the temporal bone and by the direction of their flow. A depth of about 60–80 mm points you to deeper, midline vessels, most commonly the anterior cerebral artery. Observing retrograde flow in this artery means the blood is moving opposite to the usual direction because collateral flow via the anterior communicating artery is supplying the territory from the opposite hemisphere. This reversal can happen when the ipsilateral internal carotid is occluded or severely narrowed, and a velocity around 55 cm/s falls within the typical systolic range seen in cerebral arteries. So the vessel showing retrograde flow at that depth is the anterior cerebral artery.