Horses falling down at unexpected times are a pretty common problem. When you combine 1100 pounds of nervous energy in a confined environment, it is amazing that they do not fall more. Some horses seem to have repeated episodes of falling, similar to fainting, and it occurs repeatedly under the same environmental conditions. This may be during restraint, grooming, feeding, tacking up, or even during breeding. Many of these episodes are probably a form of epilepsy or cataplexy called narcolepsy. This article discusses this disorder and possible treatments and prognosis.

Narcolepsy is the name for a type of epileptic fit where some of the sleep centers of the brain are inappropriately stimulated. The exact cause is still unknown. With stimulation the horse falls asleep, no matter where he is. There is no convulsive activity, and the horse may startle back awake or can be aroused. The sleep is paradoxical as only some of the sleep areas are activated. The EEG may be showing a wide-awake status but the horse is asleep with REM. Narcoleptic attacks result from the sequential activation of pontine a-1-adrenergic and muscarinic cholinergic systems and result in the active paralysis of skeletal muscle.

Narcolepsy has been reported in most the popular horse breeds and probably can occur in any breed. In horses no reported lesions on the brain have been reported is association with this disease, in humans narcolepsy can be caused by lesions in the rostral brain stem.