Equine seizures can be disturbing to witness, and they can be puzzling for a veterinarian to diagnose, simply because the veterinarian isn't always there to watch the horse as it has a seizure. Diagnostic tests can be expensive and time-consuming, but are necessary to determine the cause of the seizures and help identify ways to prevent them in the future. Stephanie Kube, DVM, neurology resident at the University of California, Davis, explained how to work up a horse with seizures at the 50th annual American Association of Equine Practitioners (AAEP) Convention in Denver, Colo., Dec. 4-8, 2004.

Seizures are uncontrolled discharges of neurons, and they are fairly uncommon in horses. They can be "partial" (focused in a localized area) or "generalized" (all-over) seizures, and can be caused by extracranial (outside the head) and intracranial (inside the head) abnormalities. Extracranial causes can include metabolic or toxic causes, while intracranial causes can include trauma, neoplastic growths (caused by a neoplasm, an abnormal growth of tissue whether benign or cancerous), infections, inflammation, or possibly inherited problems.

Elevated estrogen levels in mares have been known to cause seizures in mares and their foals; hypoxia (low oxygen levels), sepsis (systemic infection), and/or hypoglycemia (low blood sugar) are common causes of seizures. (Hypoglycemia can also cause seizures in adults.) True epilepsy is characterized by recurrent seizures of an undetermined cause and is thought to occur in Arabians (suspected familial inheritance), some ponies, and Paso Finos.

The diagnostic plan can include, but is not limited to, a thorough history collected on the horse, physical and neurologic examinations, development of a list of possible causes, a complete blood count (CBC), urinalysis (UA), electroencephalography (EEG, a non-invasive way to analyze brain activity), cerebrospinal fluid (CSF) analysis, and imaging, including skull radiographs, computed tomography (CT), or magnetic resonance imaging (MRI)