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Neurologic disease in horses is one of the most complicated, and sometimes frightening, areas of veterinary medicine. For Dr. Steven Reed, an internal medicine specialist at Rood & Riddle Equine Hospital, it’s also been the focus of decades of research and clinical work. At a recent Plaidcast In Person event, he walked the audience through some of the most common problems he sees: Equine Degenerative Myeloencephalopathy (EDM), cervical vertebral anomalies often referred to as ECVM, and Equine Protozoal Myeloencephalitis (EPM).
A Career in Neurology
Reed has spent nearly 50 years as a veterinarian, including over three decades teaching at veterinary schools. In recent years, he has devoted his career to neurologic cases to treat horses with gait deficits, spinal malformations, and infectious diseases of the nervous system. Through his clinical work at Rood & Riddle and his collaborations with researchers at UC Davis, the University of Pennsylvania, and other institutions, Reed has helped bring new understanding to conditions that are still only partly understood.
Equine Degenerative Myeloencephalopathy (EDM)
EDM is a degenerative disease of the spinal cord that leads to proprioceptive deficits—horses literally lose track of where their feet are. Reed explained that EDM shows up in all breeds, but recent research from UC Davis suggests a strong hereditary component in some Quarter Horse lines, possibly an autosomal dominant trait.
In Quarter Horses, signs can appear before a year of age, while in Warmbloods it’s often horses between five and eight years old. Sometimes animals have already been successful in the show ring before symptoms show. Clinical signs range from stumbling to severe clumsiness, and in some cases, troubling changes in behavior. Owners may say, “my horse doesn’t know me anymore,” or encounter sudden aggression. Reed shared an example of a horse that stopped while being lunged and charged at its handlers.
Currently, there is no test to diagnose EDM in a living horse. It can only be confirmed after death. But one encouraging finding is the role of vitamin E. If mares and foals genetically predisposed to the disease are given natural vitamin E (RRR-alpha tocopherol), they may never develop clinical signs.
Cervical Vertebral Anomalies (Often Called ECVM)
Another condition drawing attention is the malformation of the sixth and seventh cervical vertebrae. In some horses, a portion of the sixth vertebra is attached to the seventh, narrowing the canal or compressing nerves.
Reed reminded the audience that this anomaly is not new. The skeleton of Eclipse, one of the foundation Thoroughbreds, shows the same feature. What is new is how often it’s being diagnosed today, thanks to advanced imaging. Some veterinarians have even recommended automatic euthanasia when it’s found, a position Reed strongly disagrees with. “It’s been around for centuries,” he said. “We need to study it, not just sweep it under the rug.”
At Spy Coast Farm, Reed and Dr. Julie Vargas are collaborating on a Grayson-funded study to better understand how these malformations affect horses long term.
Treatment varies by case. Cervical fusion (“ventral stabilization”) can help prevent instability, though Reed noted that implanting a horse’s neck affects its resale value—most buyers will be reluctant to take it on. A newer option is a foraminotomy, a surgery that enlarges the openings where nerves exit, relieving compression without implants.
Equine Protozoal Myeloencephalitis (EPM)
EPM, caused by protozoa infecting the nervous system, is one of the most frequently recognized neurologic diseases. Reed placed it among the “big four” neurologic problems he sees, alongside EDM, cervical malformations, and herpes-related myeloencephalopathy.
Clinical signs vary widely depending on which part of the nervous system is affected. While treatments exist, EPM can be difficult to fully resolve, and some horses may retain deficits.
The Challenge of Diagnosis
Many neurologic problems present with similar signs including stumbling, weakness, or poor coordination. More than one condition can even occur in the same horse. To sort them out, Reed increasingly relies on advanced imaging. He now performs around four CT myelograms each week, though he noted the cost of a full neurologic work-up, including exams, imaging, anesthesia, and lab tests, runs about $5,000.
For owners, the decision often comes down to whether knowing the exact diagnosis will change the horse’s future.
Safety Above All
No matter the condition, Reed emphasized that safety must come first. Horses with significant neurologic deficits can be unpredictable or dangerous. “There isn’t a horse made worth getting hurt over,” he told the audience.
Some horses can be retired comfortably at pasture if they are safe in that environment. Others may reach a point where humane euthanasia is the only responsible option.
Looking Forward
Research into EDM genetics, the impact of cervical anomalies, and better diagnostic tools for EPM is ongoing. With support from organizations like the Grayson-Jockey Club Foundation and collaboration between clinics and breeding programs, progress is being made.
For owners, the best approach is vigilance: recognize early signs, seek expert evaluation when appropriate, and always weigh the horse’s, and rider’s, safety in decision-making.
Want more insight from Dr. Steven Reed? Listen to episode 445 of The Plaidcast and subscribe on your favorite podcast platform for conversations with the most influential voices in the equestrian world.
