Atlantoaxial instability secondary to agenesis of the odontoid process of the axis without rupture of the dorsal atlantoaxial ligament in dog

Resumo

Atlantoaxial instability is a congenital or traumatic or condition that causes cervical pain and varying degrees of neurological dysfunction. A case of atlantoaxial instability secondary to agenesis of the odontoid process of the axis without evidence of rupture of the dorsal atlantoaxial ligament in a dog treated sucessfully is presented. A nine-month-old male Lhasa Apso weighing 8.5 kg was referred to the Hospital de Clínicas Veterinárias (Veterinary Medical Teaching Hospital), Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre/Brazil. The neurological examination revealed hyperesthesia to palpation of the cranial cervical region, tetraparesis not ambulatory with increased reflexes and proprioceptive deficiency in the thoracic and pelvic limbs. Radiographs of the cervical spine showed agenesis of the odontoid process of the axis without evidence of atlantoaxial instability. The diagnosis of atlantoaxial instability was based on the clinical signs and radiographic examination in the ventrodorsal view. Surgical stabilization was achieved with two Steinmann pins using ventral approach. One week after the surgery, neurological examination evidenced ambulatory tetraparesis and radiograph showed alignment of subluxation and the Steinman pins correctly positioned. In the present case, the clinical improvement was attributed to the joint stabilization and fibrous tissue formation around of the atlantoaxial joint.