What is ... ?:

In this disease there is a defect in the nervous pathways that control muscle contraction. This is due to a lack of serotonin which among other functions in the body, serves as a neurotransmitter. Resting levels of serotonin appear to be normal but there is not enough available during periods of exercise or excitement. Affected dogs experience episodes of spasticity and alternating hyperflexion and extension of their legs, and become normal again with rest.

How is ... inherited?:

Inheritance is autosomal recessive.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

This disorder becomes apparent in affected dogs by 2 to 18 months of age. Dogs are normal at rest or under most conditions of light to moderate exercise. However excitement and continued or strenuous exercise bring on the signs, which range from arching of the back and a "goose-stepping" gait, to incapacitation due to paroxysms of muscular hypertonicity with alternate stretching (hyperextension) and bending (hyperflexion) of the legs.

With the cessation of the stimulus, the signs gradually subside and the dog returns to normal. Affected dogs maintain normal awareness during these episodes, and do not appear to experience pain. Your dog's general health is not affected by this condition. Episodes may increase in severity with changes in the environment or if your dog's health deteriorates for some other reason.

How is ... diagnosed?:

Your description of what occurs in your dog will be important to your veterinarian in establishing the diagnosis of Scotty cramp. If this condition is suspected, there is a specific diagnostic test using a drug that will bring on an episode of cramping in affected dogs.There are no abnormalities on routine diagnostic tests.

How is ... treated?:

There are several factors which affect the severity and frequency of hyperkinetic episodes. These include your dog's environment, his/her general health, genetic differences, and factors that modify your dog's behaviour. If you and your veterinarian can identify the conditions or behaviours that bring on Scotty cramp in your dog, you can reduce the frequency by avoiding certain situations or stimuli, or by behavioural conditioning to reduce associated anxiety.
Behavioural and environmental modification are often sufficient to reduce or eliminate episodes of Scotty cramp. When necessary, diazepam is used to treat severe episodes, and it can also be used for prevention in a situation where a dog is likely to experience clinical signs. Vitamin E can also be used to reduce the frequency of episodes.
For the veterinarian: Avoid the following drugs, which will exacerbate the frequency and severity of hyperkinetic episodes - antiprostaglandins (eg. aspirin), indomethacin, phenylbutazone, banamine, and penicillin.

For the veterinarian:

Diagnosis can be made based on clinical signs or with a methysergide (serotonin antagonist) challenge that potentiates cramping in mildly affected dogs. Administer at 0.3 to 0.6 mg/kg PO and within 2 hours there should be an increase in clinical signs with exercise. The effects last about 8 hours. Side effects include nausea, vomiting and diarrhea.

Breeding advice:

Affected dogs, their parents (carriers of the disorder) and siblings (suspect carriers) should not be used for breeding.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Fenner, W.R. 1995. Diseases of the brain. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, pp. 578-629. W.B. Saunders Co., Toronto.

Ackerman, L. 1999. The Genetic Condition: A Guide to Health Problems in Purebred Dogs. pp 142-143. AAHA Press. Lakewood, Colorado.

serotonin disorder

Scotty cramp