Surgical accessibility of the distal internal carotid artery on carotid endarterectomy evaluated using magnetic resonance angiography.

BACKGROUND: Magnetic resonance angiography (MRA) is helpful for preoperatively evaluating the degree of carotid stenosis, although it is not always useful for assessing surgical accessibility to the distal internal carotid artery (ICA) due to the lack of osteological information. OBJECTIVE: To demonstrate a method for evaluating the accessible distal portion of the ICA for carotid endarterectomy (CEA) using MRA. METHODS: As an indicator of the upper limit of the operating field, a line drawn from the C1 transverse process to the hyoid bone (C1-H line) was defined. The cross-point between the C1-H line and distal ICA was delineated on 3-dimensional (3-D) MRA and 3-D tomography angiography (CTA). The distance between the carotid bifurcation and C1-H line was measured in 11 patients. The exposed distal ICA was compared with the extent of intraoperative ICA exposure. RESULTS: The mean vertical distance (27.5 mm) from the carotid bifurcation to the C1-H line measured using 3-D MRA was almost the same as the distance (28 mm) evaluated on 3-D CTA. The discrepancy in distance between the 2 modalities was 1.9 ± 1.7 mm. Furthermore, the point of the ICA across the C1-H line created on 3-D MRA was in accordance with the intraoperative measurement (28.7 mm) of the exposed ICA. CONCLUSION: The C1-H line measured on 3-D MRA is a simple and useful indicator of the distal point of the accessible ICA during CEA, especially in patients with renal dysfunction and allergies to contrast medium.