Objective: Carotid endarterectomy without angiography is becoming increasingly common. Magnetic resonance imaging accurately demonstrates vascular anatomy and the degree of stenosis but may not localize the cervical carotid bifurcation for incision planning without tomography. We report a method for preoperative localization of the bifurcation using the relatively constant axial coplanar relationship between the horizontal petrous (C2) segment of the internal carotid artery and the external auditory canal (EAC).
Methods: The vertical distance between the midpoint of the C2 segment and the cervical carotid bifurcation was measured on magnetic resonance angiography images in five patients. Before surgery, a transverse incision was planned the same distance below the EAC. After exposure, the distance from the EAC to the bifurcation was measured with calipers. The distances from the anterior, posterior, superior, and inferior wound margins during retraction were also measured.
Results: The mean vertical distance between the C2 segment and the bifurcation was 7.2 cm on preoperative imaging and 7.6 cm between the EAC and bifurcation using intraoperative measurement (difference, 0.4 cm). The average distances between the midportion of the bifurcation and the wound margins after retractor placement were 2.9, 2.4, 2.8, and 3.5 cm for anterior, posterior, superior, and inferior measurements, respectively.
Conclusion: The C2 segment-cervical carotid bifurcation distance may be used to estimate accurately the vertical distance from the EAC to the bifurcation. When coupled with a transverse incision for carotid endarterectomy, the use of this preoperative measurement produces a target well centered within the operative field.