CVMA-ACMV

Sudden Onset of Sleep May Be Due to Narcolepsy

October 23, 2012

Narcolepsy is an uncommon disorder that results in abnormal sleep tendencies (e.g. sudden onset of sleep), sleep paralysis, and cataplexy. One of the manifestations of narcolepsy is cataplexy which is characterized by a rapid onset of sleep, resulting in flaccid paralysis that lasts for a few seconds to a few minutes.

Narcolepsy is usually hereditary and occurs in several purebreds, such as Doberman Pinchers, Poodles, Labrador Retrievers and Dachshunds, as well as mixed breeds. Most cases develop before two years of age, with more than 75 per cent occurring by six months of age.

Cataplexy causes sleep attacks. Attacks are sudden, last a short period of time, and cause no pain or residual problems. During attacks, the dog may lie in any position, its eyes open, and be aware of its surroundings.  It may be able to blink and can often be roused from an attack. However, attempts to get up may only be partially successful, resulting in immediate collapse.

Severely affected dogs can have literally hundreds of sleep attacks per day, while mildly affected ones may have no more than one or two. Cataplexic attacks are often confused with epileptic seizures.  Like epilepsy, attacks are frequently precipitated by excitement such as being fed, play time, and exercise.  Likewise, muscle twitching, closed eyelids, and vocalization can be features of both sleep attacks and epilepsy.  In the case of cataplexy, these signs are the result of REM (rapid eye movement) sleep.

Diagnostic tests are available, and usually include electromyography (muscle studies) and electroencephalography (brain wave studies). Most owners are referred to a veterinary teaching hospital for diagnostics.

Treatment may not always be necessary in all dogs, particularly if the disorder does not significantly affect the behaviour of the dog. If treatment is indicated, usually general stimulants such as methylphenidate (Ritalin7) or antidepressant, such as imipramine (Tofranil7) may be effective.  Unfortunately, even these drugs may not completely block cataplexy. If confronted with this problem, you should consult your veterinarian to confirm the diagnosis and determine the best course of action for your dog.