Myeloencephalopathy, Equine Degenerative
Basic Information 
Definition
Progressive, symmetrical neurologic condition with prominent ataxia and weakness resulting from widespread degeneration of the spinal cord and brainstem
Synonym(s)
Neuroaxonal dystrophy of Morgan horses is a related condition with similar, but more localized, degenerative histologic changes.
Epidemiology
Risk Factors
• Prolonged exposure to dry dirt lots with no grass.
• Feeding of heated, pelleted feed and sun-baked forages with very low vitamin E content (<5 U/kg dry matter).
• A familial tendency has been observed, suggesting vitamin E deficiency has a greater effect in genetically predisposed animals.
• Some chronically affected animals have been found to have normal serum vitamin E concentrations because of subsequent pasture exposure.
• Use of insecticide and exposure to wood preservative has been identified (with others) as risk factors in equine degenerative myeloencephalopathy (EDM), although a causal relationship has not been established.
Clinical Presentation
History, Chief Complaint
• Signs are first seen in suckling and weanling foals younger than 6 months.
• Signs are usually insidious in onset and slowly progressive. However, an acute onset of severe ataxia and weakness in the pelvis or all four limbs may occur.
• Clinical signs occasionally progress to recumbency, although most frequently the clinical signs plateau with maturity of the horse and chronicity of the condition.
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