Narcolepsy

What is Narcolepsy?

Sleeping PugNarcolepsy is a disease or condition of the nervous system that can affect a range of different mammals including people and dogs. Dogs and people affected by narcolepsy appear to fall asleep but remain aware of their surroundings. In the case of affected dogs, they will usually lose control of their hind legs first before collapsing in complete paralysis of their limbs. Although Narcolepsy is not always inherited, Narcolepsy in dogs is often inherited as an autosomal recessive condition in dogs, giving it the ability to skip a generation

Genetics of Narcolepsy in dogs

The genetic component of Narcolepsy does differ slightly between the different species that are affected by the condition. Dogs have a mutation in the HCRTR2 gene that can either be a point mutation or an insertion mutation in the gene that results in the condition. Narcolepsy is an autosomal recessive trait meaning that the affected dog must inherit one copy of the faulty gene from each parent to be affected. In a practical sense, as long as one parent is clear (has 2 normal copies of the HCRTR2 gene), then all of their offspring will be free of the condition regardless of the status of the dog the clear dog is bred with.

Severity of Narcolepsy in dogs

Narcolepsy is regarded to be a disease of low severity as the episodes are not painful and affected dogs do not have a shorter expected life span compared to other dogs of the same breed. In a natural situation, wild dogs that could not stay awake for long periods or “fall asleep” without warning would be at a severe disadvantage and risk of attack, but domestic dogs in a normal situation do not have these concerns.

Symptoms of Narcolepsy in dogs

The symptoms of Narcolepsy in people have been made famous in comedy movies that depict affected people as falling asleep at random moments and being unable to stay awake. This is not too far from the truth for the condition in dogs but they do often remain conscious during the episodes of collapse. Affected dogs are also ‘sleepier’ that unaffected dogs and do also fall asleep quicker and for longer periods. Dogs affected by Narcolepsy will often have episodes when they are playing or otherwise excited and typically start to show symptoms from the age of about 6 months. These episodes will last from as short as 30 seconds to as long as 30 minutes.

Diagnosis of Narcolepsy in dogs

Clinical diagnosis of Narcolepsy in dogs is difficult and the treating veterinarian will try to rule out any underlying causes for the affected dog’s episodes via blood and urine tests in combination with a physical exam. If episodes follow a predictable pattern such as within 2 minutes of physical activity, getting the dog to perform this activity in front of your vet will help with diagnosis. The inherited form of Narcolepsy in dogs can be definitively diagnosed with a DNA Disease Test to check the existence of the mutated gene responsible.

Treatment of dogs with Narcolepsy

Sleeping CavalierTreatment to prevent episodes of Narcolepsy in dogs may not be possible and there is little risk of dogs choking if an episode occurs while eating. The key here is to reduce the risks associated with an episode occurring when the dog is vulnerable so keeping the affected dog on a leash when crossing the road is an example of the lifestyle modifications an owner needs to make to keep an affected dog safe. With the right management, dogs with Narcolepsy should lead relatively normal lives.

References

Chen L et al (2009) Animal models of narcolepsy. CNS Neurol Disord Drug Targets 8(4):296-308

Foutz AS, Mitler MM, Cavalli-Sforza LL, Dement WC. (1979) Genetic factors in canine narcolepsy. Sleep. 1(4):413-21

John J, Wu MF, Maidment NT, Lam HA, Boehmer LN, Patton M, Siegel JM. (2004) Developmental changes in CSF hypocretin-1 (orexin-A) level in normal and genetically narcoleptic Doberman pinschers. J Physiol.

Kalogiannis M et al (2010) Narcoleptic orexin receptor knockout mice express enhanced cholinergic properties in laterodorsal tegmental neurons. Eur J Neurosci 32(1):130-142

Kanbayashi T et al (2000) Implication of dopaminergic mechanisms in the wake-promoting effects of amphetamine: a study of D- and L-derivatives in canine narcolepsy. Neuroscience 99(4):651-659

Lin L, Faraco J, Li R, Kadotani H, Rogers W, Lin X, Qiu X, de Jong PJ, Nishino S, Mignot E. (1999) The sleep disorder canine narcolepsy is caused by a mutation in the hypocretin (orexin) receptor 2 gene. Cell 98: 365-76

Mitler MM, Soave O, Dement WC. (1976) Narcolepsy in seven dogs. J Am Vet Med Assoc. 168(11):1036-8

Riehl J, Nishino S, Cederberg R, Dement WC, Mignot E. (1998) Development of cataplexy in genetically narcoleptic Dobermans. Exp Neurol. 152(2):292-302

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