Complete Atlanto-axial malformation in a horse. Case report

Resumo

The occipitoatlantoaxial junction allows for free movement of the head. Anomalies of the craniovertebral junction are mentioned as defects in this joint and involve different degrees of fusion of the skull and atlas, as well as of the atlas with the axis. The occipitoatlantoaxial congenital malformations are recognized in humans, horses, sheep, cattle, lions, camels, goats and dogs. This study illustrates the rare case of a merger between the first and second vertebrae of the cervical equine spine. The skeleton of a 10-year-old Quarter Horse racehorse was donated to the Federal University of Ceará. The owner reported that when the hose was alive, the animal showed resistance when turning its head to the right side, although movement to the left side was apparently normal. This peculiarity was attributed to behavioral problems. However, in this case, the Atlanto-axial malformation was found. This malformation is a complete fusion of the odontoid process of the axis with the ventral arch of the atlas and also the bilateral fusion of the axis with the lateral mass of the atlas. This merger generated a slight twist of the complex to the left side, but without neurological complications. This report is important not only because of the rarity of the vertebral malformation, but because the animal lived for 10 years without showing symptoms of any kind.