The carotid arteries are divided into the common carotid, internal carotid, and external carotid arteries, which have different internal diameters. The internal diameter of the common carotid artery is about six to seven millimeters, the internal carotid artery is about five to six millimeters, and the external carotid artery is about four to five millimeters. The carotid arteries start from the common carotid artery and branch into the internal carotid and external carotid arteries. The internal carotid arteries supply blood to the brain and the external carotid arteries supply blood to extracranial tissues and organs, making the carotid arteries important blood vessels in the head and neck. Based on the internal diameter of the carotid artery, it is not possible to determine whether the carotid artery is stenotic or not. It is necessary to use color Doppler ultrasound of the carotid artery to determine the thickness of the intima-media in order to determine whether there is stenosis of the carotid artery. If the patient has any discomfort, it is recommended to go to the hospital in time to avoid delaying the condition and causing serious consequences.