Lateral subluxation of atlanto--axial joint.
D001172:Arthritis, Rheumatoid / Q000150:complications*; D001368:Axis, Cervical Vertebra / Q000293:injuries; D001270:Cervical Atlas / Q000293:injuries; D006261:Headache / Q000209:etiology*; D006801:Humans; D004204:Joint Dislocations / Q000209:etiology