Table 2 Features of congenital ICA agenesis and acquired ICA occlusion

Congenital ICA agenesis

1) absence of the ICA;

2) the absence of ipsilateral carotid canal at the skull base;

3) the hypoplasia of ipsilateral CCA

ICA occlusion due to atherosclerosis

1) history of ischemic stroke or current ischemic stroke;

2) CT or MRI shows old infarcts in the same vascular territory;

3) CTA or DSA shows residual ICA stump;

4) CTA or DSA shows non-smooth or plaque-like narrowing of the occluded segment near the heart end;

5) carotid ultrasound shows atherosclerotic plaques at the site of occlusion; DSA, CTA or high-resolution MRI shows plaques or calcifications at the occlusion site;

6) CT bone window shows the presence of bony canals in the carotid artery.

ICA occlusion due to arterial dissection

1) recent history of neck trauma or massage;

2) often accompanied by head and neck pain;

3) CTA or DSA shows a residual lumen of the ICA;

4) CTA or DSA shows a flame-like or rat’s tail appearance of the occluded segment, occasionally shows a double-barreled appearance;

5) MRI transverse view clearly shows the cross-section of the vessel wall, with T1 sequence showing a crescent-shaped high signal intramural hematoma, and T2 sequence showing high signal intraluminal flaps.

ICA occlusion due to cardiac embolism

1) history of atrial fibrillation or cardiac valve surgery;

2) echocardiography shows atrial thrombus, valve vegetations or cardiac myxoma;

3) In cases of paradoxical embolism, echocardiography shows congenital atrial or ventricular septal defects and deep vein thrombosis in the lower limbs.