Imaging Analyses And Anatomic Study In The Malformation Of Craniocervical Region

Malformation of the craniocervical region, also known as malformation of the foramen magnum region, relates to many diseases. This paper is a study focusing upon malformation of the osseous structure, the morphologic change of the vertebral artery, and the correlated anatomy of the cadaveric specimen.Objectives: The normal vertebral artery (V3) passes through the transverse foramen and locates in the groove for the vertebral artery. It is not yet reported how the vertebral artery runs in the case of the occipitalized atlas. Osseous extruding being the root of some symptoms in the patients with malformation of the craniocervical junction, is the agent of blood vessel another etiological factor? Why do the patient with malformation of the craniocervical region often accompany with atlantoaxial dislocation? There are various surgical treatments of craniocervical malformation. It is necessary to compare and evaluate them with the aid of anatomic research.Methods: 1 ) Apply CTA reconstruction, X-ray, MRI or DSA to 30 cases of malformation of the craniocervical region. 2) Measure dry and wet cadaveric heads. The records are analysed by the statistical methods. 3) Simulate various surgical approaches in cadaveric heads by means of microscopic surgery, aiming to evaluate their advantages and disadvantages, and their respective applicability.Results:(1)Atlanto-occipital fusion is classified into 5 different types: ?The posteriorarch and the lateral mass fuse with the occipital while the anterior arch doesn't ; (2) Unilateral anterior arch, the lateral mass and the posterior arch fuse with the occipital; (3) The anterior arch, the posterior arch and the lateral mass fuse with the occipital; (4) The posterior arch partly fuses with the occipital, while the anterior arch and the lateral mass don't; (5) The lateral mass fuses with the occipital condyle. The anterior and the posterior arch do not fuse with the occipital.(2)Anomalies of the vertebral artery are classified into three types in the case of the atlanto-occipital fusion. Type I: Bilateral vertebral arteries go between the fused atlas and occipital. Type II: Bilateral vertebral arteries go between the atlas and the axis. Type III: One unilateral vertebral artery goes between the atlas and the axis, the other between the atlas and the occipital. When the head turns sideways, occlusion or stenosis of the vertebral artery may occur at the level of C1-C2. The result is vertebrobasilar insufficiency.(3)The lateral atlantoaxial joint surface is tilted in the sagittal plane or occipito-atlanto-axial joints are asymmetric. Each of the case may result in atlantoaxial dislocation.(4)The study of atlantodens interval (ADI) of the wet cadaveric heads produces no statistical difference between children and adults. The different ADIs of cadaveric specimens as shown in the X-ray examination stem from difference in calcified cartilage. Different adults may as well show difference in calcified cartilage.(5) During the resection of the dens in the lateral-transcondylar approach, removing part of the lateral mass may provide adequate exposure. The resection of the occipital condyle is unnecessary.Conclusions:(1) Malformation of the osseous structure in the craniocervical region is complicated. General X-ray or CT cannot expose its whole structure. 3-D reconstruction images have important diagnostic value.(2) There are a lot of anomalies of the vertebral artery in patients with atlanto-occipital fusion. A knowledge of these anomalies helps understand vertebrobasilar insufficiency and avoid any possible injury to the vertebral artery during the operation.(3)The knowledge of the anatomic structure of the craniocervical region is a prerequisite for the selection of operation approaches and the improvement of the operation.