Equine Degenerative Myeloencephalopathy Study Guide

Overview and Clinical Importance

Equine neuroaxonal dystrophy (eNAD) and equine degenerative myeloencephalopathy (EDM) are inherited neurodegenerative disorders affecting the brainstem and spinal cord in horses. These conditions represent a spectrum of the same disease, with EDM being the more advanced form that includes spinal cord involvement. They are among the top three causes of spinal ataxia in horses euthanized for neurologic disease and have been identified as the second most common cause of spinal cord disease at multiple veterinary teaching hospitals.

The disease is characterized by symmetric proprioceptive ataxia that typically develops in young horses between 6 to 24 months of age. The condition results from a combination of genetic susceptibility and vitamin E deficiency during critical developmental periods. Understanding this disease is essential for NAVLE preparation as it represents an important differential diagnosis for any young horse presenting with symmetric ataxia.

Etiology and Pathophysiology

Disease Mechanism

eNAD/EDM is a neuraxonal dystrophy characterized by progressive degeneration of specific neuronal populations in the brainstem nuclei and spinal cord. The pathogenesis involves the interaction between genetic susceptibility and environmental factors, primarily vitamin E deficiency during early development.