Equine Neuroaxonal Dystrophy and Degenerative Myeloencephalopathy.

Neuroaxonal degenerative disease in the horse is termed equine neuroaxonal dystrophy (eNAD), when pathologic lesions are localized to the brainstem and equine degenerative myeloencephalopathy (EDM) and degenerative changes extend throughout the spinal cord. Both pathologic conditions result in identical clinical disease, most commonly characterized by the insidious onset of ataxia during early development. However, later onset of clinical signs and additional clinical features, such as behavior changes, is also observed. A definitive diagnosis of eNAD/EDM requires histologic evaluation of the caudal medulla and cervicothoracic spinal cord. Strong evidence has suggested that eNAD/EDM is an inherited disorder and there seems to be a role for vitamin E acting as an environmental modifier to determine the overall severity of the phenotype of horses affected with eNAD/EDM.