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Surgical anatomy of the vertebral artery at craniovertebral junction level

par Bruneau, Michael ;George, Bernard
Référence Surgery of the Cranio-Vertebral Junction, Springer International Publishing, page (43-59)
Publication Publié, 2019-01

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Résumé :

The suboccipital segment of the vertebral artery that courses at the craniovertebral junction level, also called the V3 segment, extends from the transverse foramen of the axis to the dura mater of the foramen magnum. This segment is composed of three portions: a vertical portion, located between the C2 and C1 transverse foramina; a horizontal portion, above the posterior arch of the atlas; and finally an oblique portion, along the step formed medially by the bone of the C1 posterior arch. The vertebral artery is tightly anchored at the dura mater of the foramen magnum along its course through it; this junction is called the distal dural ring. Along its course, the vertebral artery V3 segment is surrounded by a venous plexus inside a periosteal sheath. The relative positions of the vertical and horizontal portions are variable, depending on head turning. In neutral position, both segments are perpendicular while they become more and more parallel as the head is turned toward the contralateral side. Many anatomical variations are present at this level; these are important to know and to detect preoperatively for working in safe conditions. It is relatively common that the vertebral arteries are of different sizes. A small vertebral artery is either hypoplasic, if the vessel participates to form the basilar trunk, or atretic, if it ends by the PICA or another vessel. Abnormal course of the vertebral arteries, persisting congenital anastomoses, duplications or fenestrations can also be present, as well as a lot of variations of the PICA.