Ventral occipito-atlanto-axial fluid-filled lesion causing dynamic spinal cord compression in a cat

Cystic lesions affecting the vertebral canal or spinal cord have rarely been reported in cats. A 3-year-old female neutered domestic longhair cat presented for evaluation of a 2-year-history of episodes of ataxia and paresis affecting all limbs. Neurological examination was consistent with a lesion in the C1-C5 spinal cord segments. Magnetic resonance imaging (MRI) showed a fluid-filled lesion at the occipito-atlanto-axial region causing dynamic spinal cord compression on flexion of the neck. The imaging characteristics were compatible with a juxta-articular cyst. To our knowledge, this is the first report of a fluid-filled lesion causing dynamic cervical spinal cord compression in a cat and highlights the importance of performing flexion-extension MRI views in diagnosing cases with dynamic spinal cord compression.