Malformação Occipitoatlantoaxial congênita em potro da raça brasileiro de hipismo - relato de caso

Abstract

Occipitoatlantoaxial malformation (OAAM) is the only described type that affects the development of the occipital bone, atlas, axis, and the joints between these structures. This condition may lead to an instability and misalignment of the cervical spine, causing neurological symptoms and potentially fatal complications. A 12-hour-old Brazilian Sport Horse foal, presenting signs of dysmaturity, was referred to the Veterinary Teaching Hospital from the Universidade Federal de Minas Gerais, Belo Horizonte, Brazil. Clinically, neurological signs such as difficulty in maintaining head posture, tetraparesis and asymmetric ataxia were observed, raising suspicion of cervical vertebrae abnormalities. Radiographic analysis revealed occipitalization of the atlas with asymmetric fusion of the atlas to the occipital bone and dorsal luxation of the axis, all findings confirmed at necropsy. Additionally, histopathology revealed axonal degeneration at spinal cord and pons as a result of nervous tissue compression at the atlantooccipital fusion area. Congenital occipitoatlantoaxial malformation (OAAM) was the definitive diagnosis in this case and to the best of our knowledge it is described for the first time on a Brazilian Sport Horse.