Carotid-anterior cerebral artery anastomosis: MR angiographic features and literature review.

Carotid-anterior cerebral artery anastomosis is a rare anomaly of the anterior part of the circle of Willis. We report here magnetic resonance (MR) angiographic findings in 2 patients with this anomaly. MR angiographic source images are useful in evaluating the anatomical details of this anomaly. Including the 2 present cases, 27 patients with this anomaly have been reported in the English-language literature. Thirty anomalous arteries were found in the 27 patients (R/L/bilateral=22/2/3). The reason for the right-sided predominance is unknown.