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Hypomyelination in Cats

A fatty substance that covers the axons (the portions of the nerve cells that transfer impulses to other cells of the body), myelin serves an important function for the nerve cells: as an insulator, protecting the nerve from outside influences, and as an aid for forwarding the process of cellular transmission of nervous system actions. Therefore, hypomyelination, or an insufficient production of myelin in the body, can be devastating for the central nervous system (CNS). It can even cause tremors, which are most apparent when the cat is active.

CNS hypomyelination has a higher rate of diagnosis in the Siamese breed.

Symptoms

Central nervous system:

• Clinical signs appear within days of birth
• Body tremors that worsen with activity and decline during rest
• Symptoms generally improve by one year of age

Peripheral Nervous System:

• Clinical signs appear at 5–7 weeks of age
• Weakness
• Incoordination of the rear limbs (ataxia)
• Muscle wasting
• Hyporeflexia (below normal or absent reflexes)
• Symptoms do not resolve with age

Causes

• Cause is unknown, but viral or toxic sources are considered, especially since symptoms often resolve
• Peripheral nervous system disease origin is undetermined, but is suspected to be genetically based

Diagnosis

Your veterinarian will perform a thorough physical exam on your cat, taking into account the background history of symptoms and your cat's genetic background. Standard tests include a blood profile, including a chemical blood profile, a complete blood count, and a urinalysis.

Diagnosis is based on the clinical signs that your cat is presenting, but for a conclusive diagnosis, your veterinarian will take a sample/biopsy of the nerve to analyze for sufficient myelin at the axon of the nerve. Your doctor may also choose to perform a brain biopsy. Other techniques include electromyography, which measures the electrical activity and potential of the muscle cells. In this case, the finding is usually normal to mild spontaneous activity. Motor nerve conduction velocity can be used to assess the ability of the motor and sensory nerves to conduct electricity. With hypomyelination, there is usually slowed conduction or only a small amount of potential.

Treatment

There is no effective treatment available for either peripheral or central hypomyelination.

Living and Management

Due to the genetic bases of this disease, if your cat has been diagnosed with this nerve disorder, you will be advised not to breed your cat, or to further breed the parent of the diagnosed kitten. If your cat is affected by CNS hypomyelination, the nervous symptoms will usually improve my the time your cat reaches its first year of age. With PNS hypomyelination, affected cats are expected to have a normal lifespan.