A Microsurgical Study Of The Complex Of The Vertebral Artery

As the development of the microneurosurgical techniques, more and more neurosurgeons have paid attention to the studies of the microsurgical anatomy. The complex of the vertebral artery (VA) lies in the suboccipital region, because of its deep location and many vital structures involved, the neurosurgeon must master the anatomy, and the adjacent relationships of the VA complex. The suboccipital region contains the complex of the VA, its periarterial autonomic neural plexus, its branches, and the adjacent spinal nerves, all of which are cushioned in a venous compartment. This region can be the site of vascular, neoplastic, degenerative, congenital, or traumatological diseases. At present, the operative approaches in which related the suboccipitial region included transcondylar approach, median inferior suboccipital approach, paramedian approach, lateral approach and far-lateral transcondylar approach. We studied the microsurgical anatomy of this region concentrating on the third segment (V3) of the VA, from which extends the transverse foramen of the axis to the dural penetration by the VA, we paid particular attention to the loops, branches, supporting fibrous rings, and surrounding venous structures of the Va, as well as the relationship between their anatomical elements and their surrounding structures.In this study, the craniocervical regions of fifteen adult cadaver heads (30 sides) were dissected with the aid of an operating microscope. All specimens previously had been embalmed in a formalin solution. In order to obtain some importance anatomic parameters for neurosurgeon guide procedures in operation and avoid some severe complications as possible as in the clinic, the anatomical marks that are important to the surgical approach were investigated, the distance between these landmarks were measured.Our study showed the following: mastoid process, transverse process of the atlas, and occipital condyle were important signs, superior and inferior suboccipital triangle is the important mark for distinguishing vertebral artery. The V3 is subdivided into two parts: a horizontal (Vsh) that is cushioned in a venous compartment, and a vertical (V3v) that is surrounded by a venous plexus, abundant venous plexus around VA was the important bleeding source during operation. Each of the V3h and the V3V has two branches: muscular and posterior meningeal of V3h, muscular and radiculmuscular of V3v. Measurements for the following anatomical structures were obtained with the aid of a microscope, the distance between mastoid process and transverse process of the atlas, occipital condyle, and superior lateral loop; the distances between the midline and the V3 at three levels: 1) the distal (dural) ring; 2) the intersection with the anterior ramus of the C-2; and 3) the upper level of the transverse foramen of the atlas; the diameter of V3h at the origin of the muscular artery and at the sites of penetrating the dural ring; the width of the V3 at the intersection with the anterior ramus of the C-2 and at the sites of penetrating the transverse foramen of the atlas. At the same time we also discuss various functional roles of the complex of the vertebral artery and its relationship to the adjacent structures and the clinical and surgical implications of these factors.