Ulcer crater or niche is a circular depression or pit on the surface of plaque with elevated margins.
Plaque at carotid bifurcation cause focal stenosis, when ulcerate becomes source of cranial emboli.
Majority of the cerebral ischemic symptoms associated with embolism from this ulceration.
Severity of stenosis and presence of plaque ulceration are the two things often taken into consideration while making decisions regarding carotid endarterectomy.
Diagnosis of plaque ulceration has remained a subject of dispute and the major factor contributing to this is the inaccuracy and subjectiveness noted in the imaging modalities.
In studies conducted to compare radiological finding by angiography and surgical findings by direct observations made during endarterectomy, large amount of discrepancy noted between the two. Accuracy of detecting ulcer from angiographic film is relatively poor. Compared with the surgical findings, sensitivity and specificity of angiographic evaluation were 45.9% and 74.1%, respectively. The rates of false positive and false negative results with angiographic detection of plaque ulceration were both high (25.9% and 54.1%, respectively).
Regardless of the disagreement between angiographic review and observations made during endarterectomy, angiography is the only practical preoperative investigative tool.