It rapidly diminishes in size as it travels up the neck, owing to the number and large size of its branches.
Relations
At the origin, external carotid artery is more medial than internal carotid artery. When external carotid artery ascends the neck, it lies more lateral than internal carotid artery.[2]
Posterior auricular artery anastomose with occipital artery, another branch of external carotid artery.[2]
One of the branches of superficial temporal artery anastomose with lacrimal and palpebral branches of ophthalmic artery.[2]
Development
In children, the external carotid artery is smaller than the internal carotid; but in the adult, the two vessels are of nearly equal size.
Diagnostics
The condition and health of the external carotid arteries is usually evaluated using Doppler ultrasound, CT angiogram or phase contrast magnetic resonance imaging (PC-MRI). Typically, blood flow velocities in the external carotid artery are measured as peak systolic velocity (PSV) and end diastolic velocity (EDV).[4]
PSV values greater than 200 cm/s are considered to be predictive of more than 50% of external carotid artery stenosis.[5]