Unusual features in horses with neuroaxonal degeneration

This is surprising: older horses, mostly Warmbloods, with neurological disease were found to have lesions most consistent with EDM. Previously, this was thought of as a disease of younger hot-blooded horses. This complicates the diagnosis of ataxia and behavioral changes in older horses as a conclusive antemortem diagnosis remains elusive.
DrO

Clinical and histopathological features in horses with neuroaxonal degeneration: 100 cases (2017-2021)
J Vet Intern Med. 2023 Dec 14. doi: 10.1111/jvim.16969. Online ahead of print.
Authors
Kara A Brown 1 , Susan J Bender 2 , Amy L Johnson 1
Affiliations

1 Department of Clinical Studies-New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, Pennsylvania, USA.
2 Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA.

PMID: 38095342
DOI: 10.1111/jvim.16969

Abstract

Background: Adult horses with proprioceptive ataxia and behavior changes that have histologic lesions consistent with neurodegenerative disease have been increasingly recognized.

Hypothesis/objectives: Describe the history, clinical findings and histopathologic features of horses presented to a referral institution with neuroaxonal degeneration.

Animals: One hundred horses with a necropsy diagnosis of neuroaxonal degeneration compatible with neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM).

Methods: Retrospective study of horses presented to the University of Pennsylvania, New Bolton Center, between 2017 and 2021 with a necropsy diagnosis of eNAD/EDM.

Results: Affected horses had a median age of 8 years (range, 1-22), and the majority were Warmbloods (72). Sixty-eight horses had behavioral changes, and all 100 had proprioceptive ataxia (median grade, 2/5). Fifty-seven horses had abnormal findings on cervical vertebral radiographs, and 14 had myelographic findings consistent with compressive myelopathy. No antemortem diagnostic test results were consistently associated with necropsy diagnosis of neurodegenerative disease. All 100 horses had degenerative lesions characteristic of eNAD in the brainstem gray matter, and 24 had concurrent degenerative features of EDM in the spinal cord white matter.

Conclusions and clinical importance: Clinical and histopathologic findings in this large group of horses with neurodegenerative disease were most consistent with eNAD/EDM, but with a different signalment and clinical presentation from earlier descriptions. The increasing occurrence of neurodegenerative disease in horses and the safety risk posed emphasize the importance of focused research in affected horses.

Keywords: ataxia; cervical myelopathy; dystrophy; equine degenerative myeloencephalopathy; warmblood.

© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.