Narcolepsy and Cataplexy in Dogs

Narcolepsy is a rare condition characterized by excessive sleepiness and brief attacks of cataplexy or muscle weakness. In humans, it affects about 0.05% of the population. The percentage of dogs with the condition is not known; it is more common in some breeds especially Doberman Pinschers and Labradors. The Canine Narcolepsy Colony at Stanford University focuses on breeding and studying dogs with narcolepsy. In dogs, cataplexy is the defining symptom. Cataplectic attacks often occur in response to a stimulus that generates excitement, such as food or toys. The dog usually passes through three stages with measurable changes in their brains: the first stage is characterized by paralyzed muscles but waking EEG in the brain and normal visual tracking; in the second the brain reaches a sleeping state similar to REM, while in the third, normal EEG returns before the dog wakes up. The episode is usually brief, but if the stimulus continues, the dog may experience another attack. Dogs with narcolepsy also appear somewhat inactive during the day, but sleepiness is less common or less noticeable than in humans. It’s not known if dogs experience hallucinations as humans do. Narcolepsy is caused by lower than normal levels of a neuropeptide called orexin (or sometimes hypocretin) in the brain. This chemical controls alertness and has a significant effect on sleep patterns. Most cases of narcolepsy in dogs are genetic, but the condition can also be acquired later in life. It is not harmful and usually does not affect the length of the dog’s life.

If the levels of certain neuropeptides in the brain are deficient, it can cause sudden episodes of sleepiness. Veterinarians call this condition narcolepsy. In dogs, cataplexy, or sudden muscle weakness, is the most common, noticeable symptom. The episodes do not cause any harm, but there is no cure and dogs will have this condition throughout their lives.

Cataplectic attacks can appear similar to a seizure but without symptoms of excessive salivation, incontinence, or labored breathing. These are some of the signs to look for.

• Sudden collapse or falling
• Drooping spine
• Legs buckling suddenly
• Rapid eye movements or twitching
• Sudden unexplained sleep
• Symptoms appear at predictable times such as feeding or play
• Lack of activity or tendency to sleep during the day

Types 

Two types of narcolepsy have been documented.

• Familial – most cases are genetic; dogs with the gene usually develop symptoms before they are six months old and most cases are mild
• Sporadic – dogs can develop this condition later in life; in sporadic cases, the symptoms tend to be more severe, although this isn’t absolute

The mechanisms that generate narcolepsy aren’t fully understood, but these are some of the factors which can cause or contribute to the condition.

Familial cases are probably due to a faulty orexin receptor that is inherited as a recessive gene. A number of breeds are known to carry this gene.

• Doberman Pinschers
• Labrador Retrievers
• Dachshunds

Autoimmune response – the immune system seems to destroy some neuron cells at the beginning of the disease in familial cases. This may also be a factor in sporadic cases. Sporadic cases are caused by a decrease in orexin levels, probably as a result of neural degeneration.

Diagnosis of narcolepsy and cataplexy in dogs is usually based on the symptoms. The veterinarian will need a thorough description of exactly what happens when your dog has an episode. If it’s unlikely that your dog will exhibit symptoms in the veterinarian’s office, try to video an incident for the vet to watch. Family history and age will help diagnose conditions that are hereditary, so this information is extremely important. 

The veterinarian will try to eliminate other potential causes, such as seizures or syncope (fainting episodes) and ensure your dogs is otherwise in good health. This may include checking your dog’s vital signs as well as blood and urine tests. An x-ray of the brain could be needed to check for tumors or lesions, especially in older dogs. Sampling of cerebrospinal fluids also show lower orexin levels with narcolepsy and this can help to diagnose sporadic cases.

Narcolepsy isn’t harmful to dogs and it doesn’t get progressively worse with age. Dogs will usually show similar symptoms throughout their lives. Mild symptoms don’t need any medical treatment. Severe symptoms that hinder a normal lifestyle can be treated with anti-cataplectic medication. One of two medications is usually prescribed; physostigmine can reduce the frequency of attacks, while imipramine can make the symptoms less severe.

In some cases, puppies that are at risk of developing the disease are given an immunosuppressant starting about three weeks of age. This can lengthen the time it takes for the disease to manifest as well as make the symptoms less severe.

There is no cure for narcolepsy and dogs will continue to show symptoms throughout their lives. Most dogs with mild symptoms still make good pets and live long fulfilling lives. Symptoms that are causing a problem can be treated with medication. It’s best to use the lowest effective dose and discuss any side effects with your veterinarian. Researchers are still experimenting with ways to artificially introduce orexin into the brain. This could potentially eliminate the episodes, if an effective method is found, however trials still remain only minimally successful.