Anatomic Variation Related To Atlanto-Axial Joint And Their Imaging Diagnosis

Background: Anatomic variation related to atlanto-axial joint mainly refers to the abnormality of the atlanto-axial joint and surrounding structures, which may cause pathologic changes and dysfunction, which could be life-threatening in some extreme cases. There is no specificity in clinical manifestation of these patients, so it is easy to cause misdiagnosis or missed diagnosis.Objectives:(1) To show anatomic variation related to atlanto-axial joint;(2) to understand their occurrence and diagnosis methods;(3) to improve the level of clinical diagnosis and treatment on the anatomic variations by analyzing incidence of patients and application of imaging exam.Methods:(1) 590 patients with anatomic variation related to atlanto-axial joint were achieved from the PACS in our hospital from January 2010 to October 2015.(2) Imaging and clinical manifestations of anatomic variation related to atlanto-axial joint were analyzed,as well as the type of variation on the characteristics of structural variation.(3) 3D imaging was used and anatomic variation related to atlanto-axial joint was analysed.(4) Imaging examination methods were compared.Results: 1. 590 patients with anatomic variation related to atlanto-axial joint included 293 cases in male(49.66%) and 297 in female(50.34%), there is no statistical difference between male and female cases. Anatomic variations were divided into Type 1 of variation 419 cases( 71.02%); Type 2 of 113(19.15%), including 10 cases of atlanto-occipital fusion, 9 cases of atlanto-axial fusion, 84 cases of C2-3 fusion, 5 cases of odontoid variation and 5 cases of hypoplasia of posterior arch of atlas; Type 3 of 26 cases(4.41%), including anomalous vertebral artery, including 5 cases of vertebral artery course variation, 4 cases of developmental anomalies of the vertebral artery, 14 cases of delicate vertebral artery, 3 cases of vertebral artery absence; Type 4 of 32 cases(5.42%), including 20 cases of Chiari malformation, 5 cases of platybasia and 7 cases of basilar invagination. 2. Clinical manifestations: manifestations of patients with anatomic variation related to atlanto-axial joint are as follows:(1) manifestation of cervical cord compression: numbness or soreness on the neck and shoulder and upper limbs, atrophy of partial tendon and so on, totaling 319 cases(about 54.07%);(2) manifestations of intracranial hypertension: obvious head ache, nausea and vomit, papilledema and so on, totaling 95 cases(about 16.10%);(3) accompanied brain dysfunction: hemiplegia caused by cerebral hemorrhage or cerebral infarction, cerebellar damages such as ataxia and nystagmus, totaling 11 cases(about 1.86%);(4) 165 cases discovered by physical examination, trauma, unknown medical history or other diseases(about 27.97%). 3. Imaging diagnosis: Type 1 variations discovered by X-ray, CT and MRI were 357 cases(60.51%), 93 cases(15.76%); and 0 case(0.00%) respectively; type 2 variations discovered by X-ray, CT and MRI were 4 cases(0.68%), 65 cases(11.02%), 15 cases(2.54%) respectively; type 3 variations discovered by X-ray, CT and MRI were 20 cases(3.39%), 6 cases(1.02%), 0 case(0.00%), respectively; and type 4 variations discovered by X-ray, CT and MRI were 17 cases(2.88%), 6 cases(1.02%) and 24 cases(4.07%) respectively. Two or more imaging examinations were used in 15 patients, of which 11 cases were not consistent in their diagnosis, which occurred in the variation of type 2, then the accuracy rate of three-dimensional reconstruction was 100%.Conclusions: Occurrence of anatomic variation related to atlanto-axial joint is 7.13%,and it is no significant difference between the male and female. In our categories, the most variations are the ponticulus posticus and fusion of C2-3, most of are diagnosed by the X-ray. Anomalous of vertebral artery are diagnosed by 3DCT and Chiari malformation by MRI. The most common clinical manifestations of patients with anatomic variation are the numbness or pain on the neck,shoulder and upper limb, followed by the headache. Variations of type 2 are diagnosed by imaging examination with high inconsistent each other, the diagnostic accuracy will be improved with three-dimensional imaging.