What is the craniocervical junction? The craniocervical junction/craniovertebral junction refers to the transitional area between the occipital bone and the 1st-2nd cervical vertebrae, which functions as the conduit for much of the head movement and also houses the medulla oblongata to cervical medulla transition area. What is a craniocervical junction deformity? The most common ones are atlanto-occipital fusion (also known as atlanto-occipitalization, atlanto-axial assimilation, etc.), congenital dentate discontinuity, and cervical 2-3 fusion. However, there are many ambiguities in the concept of this disease, such as congenital/developmental? What is the relationship with klippel-feil syndrome, and so on! Craniocervical is easy to understand, it is between the head and the neck (craniocervical junction); craniovertebral is difficult, it actually refers to between the skull and the spine (craniovertebral junction). These two terms foreigners from the beginning to engage in word games, our national translation continues to play! Fortunately, no one seems to say craniovertebral junction, no maybe someone has said so, can not remember. I this kan these concepts, just do not want to confuse people. Talking about klippel-feil syndrome, it refers to the triad of short neck, low posterior hairline and limited neck movement. This term is a symptomatic diagnostic term, and later, with increased awareness, it is now mostly referred to specifically as cervical segmentation failure (segmentation failure), which means that there is a congenital cervical fusion. In fact, not all patients with klippel-feil syndrome have bony deformities of the upper cervical spine; I remember that there is literature that only about 50% of patients have them. Other fusions such as cervical 5-6 fusion, and some patients have 3 fusions. Among these, atlanto-occipital fusion and cervical 2-3 fusion can be classified as congenital craniocervical junctional deformity. Is congenital craniocervical junction deformity congenital? Of course, since it is so called, it is. The core of the question is that the imaging changes found on examination at the time of presentation may not always be present at birth. The most typical is atlantoaxial subluxation, if all the features of the deformity are present at birth, then clinical symptoms should appear immediately, but in fact most cases of craniocervical junction deformity are in adults, not many in children, and rarely in infants and children! This indicates that the onset of the disease is progressively aggravated with growth and development until clinical symptoms appear. In other words, the skeletal form of the deformity evolves, at least in part, gradually. Atlanto-occipital fusion / atlanto-axial assimilation / atlanto-occipital ossification; what are the symptoms of craniocervical junction deformity? There can be a short neck, low posterior trajectory, and limited cervical movement; there can be progressive increased weakness of the extremities; there can be symptoms of spinal cord hollowing (sensory dissociation, i.e., hyperalgesia with preserved tactile sensation) Treatment selection and evaluation of craniocervical junctional deformity The core problem of craniocervical junctional deformity is compression of the medullary junctional region of the extension due to atlantoaxial subluxation and flattening of the skull base or cranial base entrapment, and treatment centers on decompression and resolution of atlantoaxial instability. Two types of surgery are therefore involved, decompression of the craniocervical junctional area and internal fixation of the craniocervical junction. The currently accepted standard is transoral dentatectomy and posterior atlantoaxial internal fixation, and there are many historical variations regarding this component. The basic principle is that the compression of the medulla-spinal cord in the atlanto-occipital region due to atlanto-axial dislocation/flattened skull base/cranial base entrapment is often anterior, mostly posterior/superiorly displaced after dislocation, and removal of the dentate can directly relieve the specific area of compression and improve symptoms, even if the medulla posteriorly The lower herniated cerebellar tonsils of the medulla oblongata can be repositioned and the spinal cavity can be reduced. The standard approach for transoral dentatectomy is to open the oral cavity with an opener, cut along the midline of the posterior pharyngeal wall (pharyngeal suture), separate the muscles on both sides to reveal the anterior part of the atlantoaxial spine, gradually grind away the dentate or cut the heel of the dentate and the ligaments associated with the dentate (apical ligament, pterygoid ligament, etc.) and then peel off and remove the dentate. There are many difficulties with this surgical approach, firstly the access distance is long, deep in, narrow in view, or to use a more western description, the access corridor is narrow! Secondly, the surrounding structures are extremely important, and structures such as the vertebral artery/superior cervical medulla do not allow any excessive manipulation, stabbing/squeezing/pressing/drawing/pushing, etc. Thirdly, the dentate process needs to be removed gradually or taken out as a whole. Fourth, control of the degree of dentate resection requires a lot of experience, and it is not uncommon to see inadequate resection in past cases. Fifth, the dura behind the pivotal cone is easily damaged and may lead to cerebrospinal fluid leakage and intracranial infection if not handled properly.