Epilepsy in horses is a neurological disorder characterized by recurrent, unprovoked seizures arising from paroxysmal abnormal electrical discharges in the brain. A single seizure caused by a systemic event — hypoglycemia, endotoxemia, or hepatic encephalopathy — is not epilepsy; the diagnosis requires at least two seizures with no identifiable systemic trigger. The distinction matters because management, prognosis, and veterinary workup differ substantially between systemic and primary epileptic events.
Epilepsy is uncommon in horses compared to small animals. When it occurs, it is more frequently seen in foals — neonatal seizures are a recognized component of neonatal maladjustment syndrome (sometimes called “dummy foal”) — than in adult horses. Adult-onset epilepsy in horses most often has a structural cause: cerebral trauma, abscess, neoplasia, or cholesterol granuloma in the choroid plexus. True idiopathic epilepsy analogous to human primary generalized epilepsy is reported but rare.
Seizure presentation in horses ranges from focal signs (muscle fasciculation, head tremor, asymmetric facial movement) to generalized tonic-clonic episodes in which the horse loses consciousness, falls, and exhibits violent paddling or rigid extension of the limbs. These episodes are dangerous for both the horse and any person nearby; the priority during a seizure is removing personnel from the immediate area and preventing the horse from injuring itself on fixed objects. Post-ictal disorientation lasting minutes to hours is common.
Diagnosis requires ruling out systemic causes through complete blood count, metabolic panel, and hepatic function tests before attributing recurrent seizures to a primary neurological process. Advanced imaging (MRI or CT) is used where available to identify structural lesions. Long-term management with phenobarbital or other anticonvulsants has been used in horses that are valuable and have responsive seizure patterns, though the practical safety of keeping an epileptic horse in work is a separate question that must be addressed with the attending veterinarian. See also endotoxemia as a systemic trigger that must be excluded before attributing recurrent seizures to a primary neurological process, and the true cost of horse ownership for realistic budgeting when managing a horse with a chronic neurological diagnosis.
Further Reading: Seizure disorders across animal species, including the distinctions between idiopathic epilepsy and symptomatic seizures, are covered on Wikipedia’s Epilepsy in animals article. Utah State University Extension covers clinical presentation and management of equine seizures at USU Extension: Seizures in Horses.