Radiographic features of atlantoaxial instability in an adult canine – case report

This report describes the radiographic findings in a case of atlantoaxial instability associated with agenesis of the odontoid process of the axis in an adult dog. Clinically, the patient presented apathy and tetraparesis. A simple radiographic examination of the cervical region was performed, which allowed the disclosure of agenesis of the odontoid process of the axis without articular changes. The atlantoaxial normality index (ANI) was 0.103 mm, indicating instability of the joint. A conservative approach was adopted by means of a cervical collar, movement restriction and anti-inflammatory therapy. We concluded that asymptomatic adult animals can be carriers of this condition, and that the calculation of the ANI was an effective tool to complement the subjective radiographic evaluation of this articulation on this report’s dog. The patient remains stable with the cervical collar.