• Michaël Bruneau, Jan Frederick Cornelius, and Bernard George.
• Department of Neurosurgery, Lariboisière Hospital, Paris, France. mbruneau@ulb.ac.be
• Neurosurgery. 2006 Feb 1; 58 (1 Suppl): ONS29-35; discussion ONS29-35.

ObjectiveWe describe our surgical technique of exposure, control, and transposition of the third segment of the vertebral artery (VA V3 segment).MethodsThe VA V3 segment extends from the C2 transverse foramen to the dura mater of the foramen magnum. It initially courses vertically between the C2 and C1 transverse foramens, then runs horizontally over the atlas groove, and finally obliquely upwards before piercing the dura mater. Exposure of the VA V3 segment through an antero-lateral approach is performed by passing medially to the sternomastoid muscle. After exposure and protection of the spinal accessory nerve, the C1 transverse process is identified below and in front of the mastoid tip. The small muscles that insert on it are cut to expose the C1-C2 portion. The inferior aspect of the horizontal portion is safely separated from the atlas groove by elevating the subperiosteal plane and the superior aspect is freed by a cut a few millimeters above the VA on the occipital condyle. Complete unroofing of the C1 transverse foramen is achieved by resecting the bone while leaving intact the subperiosteal plane. The VA then can be transposed. Venous bleedings during the dissection from periosteal sheath tearing can be controlled by direct bipolar coagulation.ResultsThe control of the VA V3 segment is essentially used for lesions in the VA vicinity and to improve the surgical exposure at the craniocervical junction level. Indications therefore are tumoral removal, VA decompression, and rarely, nowadays, VA revascularization.ConclusionPerfect knowledge of the anatomy and the surgical technique permits a safe exposure, control, and transposition of the VA V3 segment. This is the first step of many surgical procedures.

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