Correlation Between Outcomes of Surgical Correction of Atlantoaxial Instability in Small Dogs and Magnetic Resonance Imaging Abnormalities

Congenital atlantoaxial instability (AAI) occurs more often in young, small-breed dogs, usually resulting from malformations in the craniocervical junction. These malformations cause atlantoaxial subluxation or luxation and compression of the cervical spinal cord. As a result, dogs can have varying levels of neurological problems. While surgery is commonly used to realign the vertebrae, outcomes after surgery vary widely, and complications are common. Magnetic resonance imaging (MRI) helps identify abnormalities in the vertebral canal, spinal cord damage, and other brain diseases, which can affect the dog’s prognosis. This retrospective study assessed MRI findings and their association with surgical outcomes in 20 dogs with AAI. Older age and certain MRI results—such as severe ventral spinal cord compression associated with greater preoperative neurological severity and syringomyelia—were associated with less favorable surgical outcomes. Many MRI abnormalities were found, but not all predicted poor outcomes. These results show the importance of thorough MRI before surgery and also suggest that a younger age and not having syringomyelia are good indicators of improved recovery after AAI surgery.