Clinical and histopathological features in horses with neuroaxonal degeneration: 100 cases (2017-2021).
Authors: Brown Kara A, Bender Susan J, Johnson Amy L
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Neuroaxonal Degeneration in Horses Between 2017 and 2021, researchers at the University of Pennsylvania's New Bolton Center reviewed necropsy records for 100 horses diagnosed with equine neuroaxonal degeneration/degenerative myeloencephalopathy (eNAD/EDM), a progressive neurodegenerative condition characterised by proprioceptive ataxia and behavioural changes. The typical patient was a Warmblood (72 of 100 cases) with a median age of 8 years, presenting with ataxia graded 2/5 or worse and neurological behavioural abnormalities in 68 cases; notably, all horses showed proprioceptive deficits. Whilst 57 horses had radiographic cervical changes and 14 showed myelographic evidence suggestive of spinal cord compression, no single antemortem diagnostic test reliably predicted neurodegenerative disease—all 100 cases exhibited characteristic brainstem lesions at necropsy, with 24 showing concurrent spinal cord white matter degeneration typical of EDM. The findings represent a shift from historical descriptions of eNAD/EDM, particularly in the increased prevalence among sport horse breeds and the variable radiographic findings, emphasising that practitioners should maintain a high index of suspicion for neurodegenerative disease in mature Warmbloods presenting with progressive ataxia and behavioural changes, even when imaging appears to show structural spinal pathology. This expanding recognition of neurodegenerative disease in equine populations carries significant implications for welfare and safety, warranting further investigation into causative factors and development of reliable antemortem diagnostic tools.
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Practical Takeaways
- •Neuroaxonal degeneration is increasing in horses and presents with ataxia and behavioral changes; warmbloods appear overrepresented in recent cases, warranting breed-specific investigation
- •Clinical signs and imaging findings (including cervical radiographs and myelography) cannot reliably diagnose neuroaxonal degeneration antemortem—definitive diagnosis requires necropsy histopathology
- •The safety risk posed by progressive neurological disease in affected horses emphasizes importance of early recognition of ataxia and behavior changes, particularly in middle-aged warmbloods
Key Findings
- •100 horses with neuroaxonal degeneration had median age of 8 years with 72% being Warmbloods, differing from earlier disease descriptions
- •All 100 horses exhibited proprioceptive ataxia (median grade 2/5) and 68 had behavioral changes; 57 had cervical vertebral radiographic abnormalities
- •All horses had degenerative lesions in brainstem gray matter characteristic of eNAD, with 24 horses showing concurrent EDM lesions in spinal cord white matter
- •No antemortem diagnostic test results were consistently associated with necropsy diagnosis of neurodegenerative disease