- Type Disease
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 hyper flexion and extension of their legs, and become normal again with rest.
- How Transferred
Inheritance is autosomal recessive.
- What to Look for
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 (hyper flexion) of the legs.\n\nWith 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.
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.
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 behavior. If you and your veterinarian can identify the conditions or behaviors that bring on Scotty cramp in your dog, you can reduce the frequency by avoiding certain situations or stimuli, or by behavioral conditioning to reduce associated anxiety.\nBehavioral 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.\nFor the veterinarian: Avoid the following drugs, which will exacerbate the frequency and severity of hyperkinetic episodes - antiprostaglandins (eg. aspirin), indomethacin, phenylbutazone, banamine, and penicillin.
- Veterinarian Information
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 Considerations
Affected dogs, their parents (carriers of the disorder) and siblings (suspect carriers) should not be used for breeding.
- Known Breeds Affected
Scottish terrier\nNorwich terrier