Clinical manifestations: 1. Pain in the cervico-occipital region and limitation of neck movement, numbness after tilting the neck back, and in anterior atlantoaxial subluxation, the anterior arch of the atlas protrudes toward the posterior pharyngeal wall, and dysphagia occurs. Abnormal head posture. 2. Symptoms of spinal cord damage, loss of sensation, weakness in holding objects, weakness in walking, unsteady gait, urinary and defecation disorders, muscle atrophy of limbs, and severe general paralysis may occur. 3. Stem compression resulting in dysarthria and dysphagia. Auxiliary examination: The increase of the distance between the anterior arch of the atlantoaxial spine and the dentate process is the main basis for the diagnosis of atlantoaxial subluxation, which is more than 3mm in adults and more than 4mm in children, and the diagnosis can be confirmed by the hyperflexion position. Three-dimensional CT can clearly show the position and morphology of atlantoaxial vertebrae, cardinal vertebrae, dentate process and atlantoaxial joints, and MRI can clearly observe the morphology, position, degree and scope of spinal cord compression. Neuroendoscopic odontoidectomy is an innovative surgical procedure that avoids the trauma of previous transoral odontoidectomy. In endoscopic odontoidectomy, unipolar electrocoagulator cuts the mucous membrane of nasopharynx, forming an inverted “U”-shaped mucous membrane flap from the lower edge of the anterior wall of the pterygoid sinus to the level of the soft palate, which reduces the occurrence of cerebrospinal fluid leakage and intracranial infections in the postoperative period. The fascia below the odontoid process to the surface of the inferior slope is incised under navigation guidance to expose the inferior slope and the fused atlantoaxial anterior arch and odontoid process. This approach is performed in the nasopharynx, avoiding direct incision of the mucosa in the oropharynx, and allows normal feeding in the early postoperative period without the need for prolonged gastric tube nasal feeding. The traditional transoral approach requires incision of the soft palate and the use of retractors, which is prone to postoperative swelling of the tongue, oropharyngeal mucosa and other upper respiratory tracts, resulting in the inability to remove tracheal intubation at an early stage, and some patients even need to undergo a tracheotomy, which causes additional pain to the patient, fully reflecting the minimally invasive operation of endoscopy. Atlanto-occipital malformation is a common disease in neurosurgery, which often develops in adulthood. It is a congenital malformation of the central nervous system with abnormal development of the occipital foramen magnum area, atlantoaxial vertebrae, and pivot vertebrae, and accompanied by the abnormal development of the nervous system and the nearby soft tissues. Atlanto-occipital malformations take various forms, including odontoid malformations, skull base depression, atlantoaxial dislocation, subcerebellar herniation, and spinal cord cavernous malformations. Currently, the treatment of atlanto-occipital malformations is aimed at decompressing the cervical spinal cord of the brainstem and reestablishing the stability of the occipitocervical region. In order to release the compression of the cervical spinal cord, in the treatment method in the past, most of the conservative treatment, such as cranial traction, Halo brace, head and neck thoracic cast, etc., but the efficacy of the treatment is relatively poor, and the individual patients may lead to exacerbation of the condition. The fundamental reason is that atlantoaxial subluxation combined with skull base deformity is different from acute traumatic subluxation, which is filled with firm fibrous connective tissue between the atlantoaxial anterior arch and the odontoid process, so it is difficult to reset the atlantoaxial joints and relieve the compression on the cervical cord through conservative treatment. The ideal surgical result is to completely relieve the compression of the anterior dentate process and the posterior atlantoaxial arch and occipital bone on the cervical cord of the brainstem and to maintain the stability of the atlanto-occipital region in the long term. Surgical approaches include suboccipital decompression via a posterior approach; anterior odontoidectomy via an oral approach; and distal-lateral or posterior-suboccipital approaches via the lateral aspect of the occipitocervical region. In patients with anterior odontoid process compression and posterior atlanto-occipital joint compression, two surgeries are often required to completely relieve spinal cord compression. In patients with significant atlantoaxial dislocation, internal fixation and fusion are routinely performed. The traditional surgical approach is usually an anterior approach with tracheotomy before anesthesia, abrasion of the odontoid process via the oropharyngeal approach, and then suboccipital decompression and occipitocervical fusion via the posterior approach after the oropharyngeal wounds have healed, which requires three surgeries. Due to the deep location of the dentate process, the operating field is narrow, the field of vision and exposure is limited, the operation is difficult, and there are many postoperative complications, high mortality rate, and extreme pain for the patients. If only posterior decompression is performed, the stability of the atlanto-occipital region is affected and the long-term results are poor. The traditional surgical treatment is decompression of the posterior cranial fossa, resection of the posterior border of the foramen magnum, simple decompression without local fixation, and the surgery has a great impact on the stability of the craniocervical junction. Instead, decompression of the posterior cranial fossa plus internal fixation of the occipitocervical implant fusion not only relieved the spinal cord compression factors, but also rebuilt the stability of the neck through internal fixation of bone grafting. Even if the spinal cord compression is relieved by the surgery and the clinical symptoms are temporarily relieved, the potential factors of instability are still not eliminated, and there is still the possibility of re-injury aggravated by subluxation in the future. Therefore, atlanto-occipital posterior decompression with atlantoaxial joint repositioning for anterior decompression and occipitocervical fixation and bone grafting fusion technique can rebuild the stability of the neck.