Did you ever wonder if your horse suffers from a sleep disorder? The only sleep disorder known to occur in horses is narcolepsy.

What is narcolepsy?

Narcolepsy is an incurable non-progressive disease of the central nervous system. In humans, narcolepsy causes excessive drowsiness during the day (sometimes a sleep-attack occurs), cataplexy (sudden loss of muscle tone), hallucinations, and sleep paralysis. In the horse and other mammals, cataplexy is the most frequently observed symptom. Excessive drowsiness can occur but is harder to observe. Cataplexy is caused by a fragmentation of the REM sleep. Cataplexy confirms the diagnosis of narcolepsy in horses. Cataplexy can be induced by an injection of physostigmine (van Nieuwstadt, RA et al., 1993). Other medications can be used to stop an episode. Either method can cause gastric disturbance.

Narcolepsy is very common in miniature horse foals, and can last for 30 seconds or so. There is indication that narcolepsy may be heritable. The symptoms of narcolepsy are different between horses to an extent, but generally consistent within an individual. Narcolepsy may be stimulated by excitement (taking a horse to a show, for example). One method of treating narcolepsy is to give the horse the long term medication emipromene, which reduced REM sleep over all. However, it may have gastric disturbances as a side effect.

Reference:

van Nieuwstadt, RA et al. 1993. Narcolepsy in horses. Tijdschr Diergeneeskd (article in Dutch). 118(23):765-8.