Equine Neuroaxonal Dystrophy (eNAD)

Ataxic horse exhibiting abnormal stance.
Ataxic horse exhibiting abnormal stance.

Neuroaxonal dystrophy is a degenerative disease of the central nervous system that affects humans, dogs, cats and many other animals.

Equine neuroaxonal dystrophy (eNAD) is degeneration of parts of the brainstem in young individuals. Equine degenerative myeloencephalopathy (EDM) is a more severe form of eNAD in which the spinal cord is also affected. However, EDM is phenotypically indistinguishable from eNAD.  Horses affected with eNAD usually present signs of mild to severe gait abnormalities (ataxia) that affect all four limbs, though the hind limbs are usually more severely affected. Clinical signs of eNAD are usually first observed in young horses (two years of age or less). Neuroaxonal dystrophy is a heritable trait analyzed in Morgans, Appaloosas, and Quarter Horses.

The disease is characterized by symmetrical ataxia, abnormal base-wide stance at rest, and proprioceptive deficits in all limbs. Signs usually develop by 6 to 12 months of age. Affected foals often have low serum vitamin E concentrations. Neuroaxonal dystrophy is clinically indistinguishable from equine degenerative myeloencephalopathy (EDM); the only difference between these disorders is the location of axonal degeneration within the central nervous system. These conditions appear to have a genetic basis, with clinical expression in genetically predisposed foals being influenced by dietary vitamin E. The genetic defect underlying development of eNAD and EDM is currently being investigated.

Are you concerned that your horse may have eNAD or EDM? Contact our lab for more information on how you can aid in equine genetic research.

Histopathological phenotype of horses affected by eNAD/EDM. Aleman et al., 2011
Histopathological phenotype of horses affected by eNAD/EDM. Aleman et al., 2011