Myelin Deficiency in Cats

Most myelin disorders are congenital and begin manifesting symptoms in cats less than a year old and often soon after birth. These disorders can affect the central nervous system and/or the peripheral nervous system. If you have a young cat that has delayed reflexes, has tremors in the limbs, trunk, and/or head (especially during or after activity), or if the cat is unable to stand or move, take the cat to your veterinarian immediately. If you have an adult cat that either gradually or suddenly develops these symptoms, your cat must see a vet immediately as the animal’s myelin may be deteriorating as the result of an acquired illness.

Myelin is the lipid membrane or sheath that covers and protects the axons, which are the slim projections that allow neurons to communicate with other cells in the central and peripheral nervous systems. The myelin membrane protects the axon like a conduit, allowing electrical information to flow safely and quickly from the neuron to the other cells. If myelin develops incorrectly, does not develop, or becomes deficient over time, severe neurological dysfunction can result. This neurological dysfunction can cause an animal to have delayed reflexes, tremor, inability to stand or move, and possibly seizures.

If a young cat has any of the following symptoms, the cat may suffer from an inherited form of myelin deficiency. If an adult cat experiences the following symptoms, the cat may have developed an extremely rare form of acquired myelin deterioration. Either form of myelin deficiency should be considered serious and may cause the following symptoms:

• Reduced reflexes and delayed movement
• A tremor in the limbs, trunk, and/or head
• An inability to stand or move
• Seizures 

Although there are many different disorders that can cause myelin deficiency in cats, most are congenital while there may be rare cases of acquired myelin deterioration. 

Congenital Myelin Disorders

Congenital Myelin Disorders include hypomyelination and dysmyelination. These conditions may be X-linked hereditary, which means the mutation is inherited from one parent’s X chromosome. Since a male kitten only needs to inherit one mutated X chromosome to inherit the disorder, while a female kitten would need to inherit two mutated X chromosomes to inherit the disorder, congenital myelin disorders are far more common in male cats than in female.

Congenital myelin disorders may also be autosomal recessive, which means the mutation is inherited from both parents, who may be carriers that have never developed any myelin disorders but pass on the gene to their offspring nonetheless.

Acquired Myelin Disorders

Acquired demyelination, usually known as demyelination, is extremely rare and veterinarians are not sure of the cause. Viruses and tainted food have been proposed as possible causes. In scientific studies on cats, irradiated food has caused sudden and severe demyelination, which later repaired itself when the cats returned to a normal diet.

If a myelin disorder is suspected, your veterinarian will begin by doing a thorough physical examination and blood tests, and asking you to describe the symptoms you have observed in your cat. A diagnosis is usually based upon at least four factors. 

• The first factor is the age of the cat at the onset of symptoms. This is important because congenital forms of myelin disorders are far more common than those acquired in adulthood. If your cat is only days, weeks, or months old when the symptoms begin, this is a very important factor in your veterinarian’s ability to make a diagnosis. 
• The second factor is the symptoms themselves. If the cat, especially a very young cat, is exhibiting the symptoms listed above, myelin deficiencies will likely be considered as the cause.
• The third factor is whether or not your cat is male. While females can suffer from congenital myelin disorders, it is much more common in males. 
• The fourth factor is the elimination of other possible causes. The veterinarian may request an MRI and other tests to make sure your cat is not suffering from another neurological disorder or injury. Although nerve biopsies may be possible and helpful, if your cat is young, has the symptoms above, and does not suffer from another condition, a myelin disorder is a likely diagnosis. 

Unfortunately, definitive diagnosis of myelin disorders can only be made by performing a necropsy after the cat has died.

There are currently no effective treatments for myelin disorders. The only way to avoid congenital myelin disorders is to avoid breeding cats that are carriers. While acquired myelin deficiencies are extremely rare and not well understood, making sure that your pet is current on all vaccinations and eats a healthy diet is important for the overall health of your pet.

Some young cats will begin to produce and repair myelin on their own over the first year of life, while others do not and suffer the symptoms of this condition for the entirety of their lives. Your veterinarian will advise you as to how to care for your affected cat and will likely want to examine your pet on a regular basis. In severe cases that do not resolve naturally over time, euthanasia may be the most humane option.