Which Doppler pattern is typical for ECA when it assumes ICA-like flow in collateral channels?

Which Doppler pattern is typical for ECA when it assumes ICA-like flow in collateral channels?

• A. Narrow systolic peaks with minimal diastolic flow
• B. Broad systolic peaks with forward diastolic flow
• C. High-resistance flow with reversed diastolic flow
• D. No flow signal

Answer: (D)

When the external carotid artery participates in collateral flow to the brain, its downstream pathways behave more like the low-resistance bed of the internal carotid circulation rather than the usual high-resistance ECA territory. This ICA-like, collateral flow produces a Doppler pattern with sustained forward diastolic flow and a broad systolic peak—characteristic of low-resistance vessels. In other words, you’d expect a waveform with forward diastolic flow rather than the sharp, narrow systolic peaks with minimal diastole seen in a high-resistance ECA. A no-flow signal would not fit this scenario, since there is active collateral streaming to the cerebral circulation.

When the external carotid artery participates in collateral flow to the brain, its downstream pathways behave more like the low-resistance bed of the internal carotid circulation rather than the usual high-resistance ECA territory. This ICA-like, collateral flow produces a Doppler pattern with sustained forward diastolic flow and a broad systolic peak—characteristic of low-resistance vessels. In other words, you’d expect a waveform with forward diastolic flow rather than the sharp, narrow systolic peaks with minimal diastole seen in a high-resistance ECA. A no-flow signal would not fit this scenario, since there is active collateral streaming to the cerebral circulation.