The distinction between the internal carotid and external carotid arteries includes positional alignment, morphologic branching, and spectral pattern on ultrasonography.
1. Positional alignment: The internal carotid artery is posterior to the external carotid artery and gradually turns from posterior lateral to posterior lateral.
2. Morphological branches: The internal carotid artery is relatively thicker than the external carotid artery, and the internal carotid artery does not have branches outside the skull, but starts to send out branches such as the ophthalmic artery after entering the skull, whereas the external carotid artery gradually divides into branches such as the superior thyroid artery, facial artery, superficial temporal artery, etc. In this case, the internal carotid artery is the most important artery.
3. Spectral morphology: the internal carotid artery is of low-resistance type, and the superficial temporal artery does not show tremor waveform on percussion test, while the external carotid artery is of high-resistance type, and the superficial temporal artery can show tremor waveform on percussion test, which is one of the main bases for distinguishing between the two in ultrasonography.
The distinction between internal and external carotid arteries needs to be made by combining the above aspects, and patients who have internal or external carotid artery disease should also seek medical treatment in a timely manner.