Narcolepsy and Cataplexy

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Narcolepsy and Cataplexy

By: Dr. John McDonnell

Section: Overview

Narcolepsy is excessive daytime sleepiness, lethargy, or brief periods of collapse and unconsciousness that resolve spontaneously. Cataplexy is characterized by brief episodes of muscle paralysis with loss of tendon reflexes; the animal stays alert and will follow with his eyes. These brief episodes of motor inhibition are completely and spontaneously reversible.

These central nervous system disorders usually occur together in most dogs although narcolepsy can occur without cataplexy. The attacks may last anywhere from a few seconds to more than 20 minutes. In between episodes, your dog is usually normal. Some pets will have from several attacks per week to hundreds per day. This disorder is extremely rare in cats.

Multiple breeds of dogs can be affected including Doberman pinscher, miniature poodle, Labrador retriever, dachshund, Saint Bernard, beagle, Afghan hound, Airedale terrier, Welsh corgi terrier, malamute, springer spaniel, standard poodle, wire-haired griffon, Australian shepherd, giant Schnauzer and Rottweiler.

There is proven heredity in the Labrador retriever, poodle, dachshund and Doberman pinscher. Genetic studies of Labradors and Doberman pinschers support a recessive inheritance with complete penetrance.

Clinical signs usually develop in animals younger than six months of age.

What to Watch For

Attacks of sleep in your pet that are typically induced by excitement (playing and eating are most common) in which your pet may fall over fast asleep with floppy muscles. Your pet may be responsive to you, but more likely he will be unconscious.

Breathing and eye muscles are usually not affected. Reflexes such as swallowing and coughing are also not affected. There is no loss of urinary or fecal continence and pets typically do not salivate or have spasmodic muscle movements during these episodes.

Check that your pet is breathing and the mucous membranes are pink.

Diagnosis

Veterinary care consists of appropriate diagnostic and therapeutic recommendations. Diseases that may mimic this condition include heart disease, seizure disorders, myasthenia gravis, low blood sugar (hypoglycemia), low blood calcium (hypocalcemia), low blood potassium (hypokalemia), low levels of oxygen in the blood (hypoxia), an underactive thyroid gland (hypothyroidism) and hypoadrenocorticism (Addison's disease).

Your veterinarian will perform a complete physical and neurological examination. The results of these tests should be normal if narcolepsy/cataplexy is the presumptive diagnosis. Your veterinarian may recommend the following diagnostic tests to rule out other possible diagnoses:

Complete blood count (CBC)

Serum chemistry profile to check for liver, kidney function as well as concentrations of blood electrolytes such as calcium, sodium and potassium

Urinalysis to check kidney function

Thyroid tests to check thyroid status

Electrocardiogram and cardiac ultrasound, especially if syncope or cardiac arrhythmias are suspected

Depending on your veterinarian's experience, these episodes may be induced with the stimulation typically responsible for the attacks such as food or excitement. Sometimes, giving a drug can induce the episodes. The event can be reversed or prevented by giving another medication.

Treatment

Primary goal is to reduce the severity and frequency of narcoleptic-cataplectic attacks. Narcolepsy-cataplexy is not a fatal disease and your pet does not suffer.

The attacks are typically not life-threatening by themselves although certain situations such as hunting, swimming or off-leash exercise should not be allowed as they may cause harm. Some pets outgrow this condition.

Some pets do not need medications, as certain triggering situations can be avoided.

Pets that require medication are usually given imiprimine, yohimbine, methylphenidate or dextroamphetamine at a frequency of 1 to 3 times a day.

All these drugs have potential serious side-effects and should not be used without direct veterinary supervision. Drug dosages and frequency determination may take some time and fine-tuning until the right combination is found. Many patients develop drug tolerance and a change may be necessary.

Monamine oxidase inhibitors are contraindicated in dogs because of possible toxic cardiovascular side effects.

Home Care and Prevention

Narcolepsy is not a fatal disease. Prognosis varies since the disease is not curable, and even with treatment some patients continue to have symptoms. If you suspect your pet is having a narcoleptic attack, you can reverse the attack by petting, talking or otherwise stimulating him.

Depending on the frequency and severity of the attacks you may not need to medicate your pet and your pet may outgrow this condition.

Since the condition may be heritable, your pet should be spayed or neutered to prevent passing this trait on to offspring.