Anatomical variations of the carotid bifurcation: implications for digital subtraction angiography and ultrasonography.

Intravenous digital subtraction angiography was used to determine prospectively the positional variations of the common carotid bifurcation in 100 consecutive patients with clinically suspected arteriosclerotic disease. The most common position (97/200, 48.5%) of the external carotid artery was anteromedial to the internal carotid artery. Position of the external carotid artery anterolateral to the internal carotid artery was noted in 26/200 (13%) bifurcations, but this anatomical variant was more common on the right (21/100) than on the left (5/100) (p less than 0.01). Practical implications may be drawn from this study. For digital subtraction angiography, the left anterior oblique view has to be considered the projection of choice and the right common carotid bifurcation is less likely to be adequately displayed than the left one; for duplex ultrasonography, optimal visualization is obtained from a posterolateral orientation of the transducer.