Which animal from the material presented had dens hypoplasia?

• A. Teacup Yorkie
• B. Arabian horse
• C. Labrador Retriever
• D. German Shepherd

Answer: (A)

Dens hypoplasia is a congenital underdevelopment of the dens (the odontoid process of the second cervical vertebra), which weakens the atlas-axial joint and can lead to atlantoaxial instability with potential spinal cord compression at the craniovertebral junction. Toy breeds, including teacup Yorkies, are described as being predisposed to this condition due to breed-specific developmental anomalies and extreme small size. Because of this predisposition, the Teacup Yorkie is the animal from the material presented that would have dens hypoplasia. Clinically, you’d expect neck pain and neurologic signs such as neck stiffness, proprioceptive deficits, or ataxia, and imaging would show a hypoplastic or absent dens with increased space between the atlas and axis, sometimes needing CT or MRI for confirmation. Larger breeds listed are less commonly associated with this particular congenital anomaly and may present with different cervical issues instead.