In a fast-growing Thoroughbred horse with progressive ataxia, which condition is most likely responsible?

The condition most likely responsible for progressive ataxia in a fast-growing Thoroughbred horse is Wobbler's syndrome, also known as cervical vertebral instability. This condition is characterized by an abnormal development of the cervical vertebrae, leading to narrowing of the vertebral canal and consequent compression of the spinal cord. In young, rapidly growing horses, particularly Thoroughbreds, the growth plates and vertebral structures can develop irregularly, which predisposes them to this instability.

As a result of this compression, ataxia, which is a lack of voluntary coordination of muscle movements, manifests due to the disruption of normal neurological pathways. The symptoms can vary in severity, but progressive ataxia is a hallmark of Wobbler's syndrome. Diagnosis typically involves clinical examination and imaging studies such as radiographs or MRI to assess the cervical spine.

In contrast, other conditions listed may also lead to neurological issues but are less typically associated with the rapid growth phase in horses. For instance, osteochondritis dissecans primarily affects joints and can cause lameness, equine protozoal myeloencephalitis is generally an infectious condition that leads to a more varied clinical presentation, and equine metabolic syndrome is related to obesity and insulin resistance