Atlantoaxial Instability (AAI) is characterized by excessive movement at the junction between the atlas and axis. This condition can be seen in any breed at any age, but mainly affects immature miniature and toy breeds. AAI is typically a congenital or developmental disease and sometimes has a traumatic origin. Abnormalities of the dens (aplasia, hypoplasia, fragmented or dorsal deviation) and absence of the transverse ligament are seen as principal causes of AAI. When spinal cord is injured clinical signs can include neck pain and varying degrees of ataxia of all four limbs, including tetraparesis and tetraplegia in severe cases. Treatment options embrace conservative and surgical management. Conservative treatment consisting of strict cage confinement, use of an immobilizing cervical splint, and the administration of corticosteroids is recommended for a restricted number of cases. Ventral surgical stabilization is traditionally the preferred treatment for AAI because it facilitates anatomic alignment, placement of autogenous cancellous bone and removal of the dens if necessary, however dorsal techniques are also described. This study contains a literature review in AAI and four cases followed at Cornell University Animal Hospital: a intact male, 7 months-old, German Shepherd, a castrated male, 12 months-old, Dachshund, a spayed female, 96 months-old, Yorkshire Terrier, and a spayed female, 24 months-old, Maltese. Patients exhibited tetraplegia, tetraparesis and cervical pain as clinical signs. Preoperative MRI or/and CT scan, and postoperative CT scan were performed. All dogs were treated surgically with multiple ventral implants and bone cement. All dogs improved their neurological status. The information presented was collected during an externship in Cornell University Hospital for Animals, in the Neurology and Neurosurgery Service.

Dissertação de Mestrado Integrado em Medicina Veterinária