Canine Myasthenia Gravis

Myasthenia gravis (MG) is a neurological disease that makes the dog weak and incapable to contract his muscles. The cause of this neuromuscular disease is the incapacity of the AChRs (nicotinic acetylcholine) nerve receptors to function at a normal rate. The disease may occur in any breed of dogs, but some breeds are genetically predisposed (i.e. Jack Russell terrier, smooth fox terrier and springer spaniel). Older dogs may get this disease also.

Causes of Myasthenia Gravis

The disease is thought to be genetic in certain dog breeds such as Jack Russell terriers, springer spaniels and smooth fox terriers.

Myasthenia gravis can also be acquired as the dog gets older (regardless of breed), being also considered an immune system mediated disease.

Symptoms of Myasthenia Gravis

The symptoms of myasthenia gravis will differ from dog to dog. The typical signs of disease include general weakness, the inability to properly contract the muscles and lethargy. Some dogs will only be unable to contract certain groups of muscles, while other dogs may be affected more, involving all the muscles. The disease will be active after the dog has performed activities, leaving him nearly immobilized; immediately after a resting period, the dog will look normal and can contract his muscles.

In older dogs that acquire the disease, the disease may start with the enlargement of the esophagus resulting in swallowing difficulties and vomiting. Aspiration pneumonia can occur and this is a dangerous condition. The dog may also lose weight, being unable to eat properly.

Diagnosing MG

If you notice signs of weakness in your dog, especially after physical activities, you should visit the vet.

Also, if your dog has difficulties in swallowing, you should consult the vet. If the vet finds that the esophagus is enlarged (megaesophagus), the dog will be tested for MG. On the other hand, if the dog is diagnosed with MG, the vet will perform an x-ray to check the esophagus to establish if it has been affected.

MG can be diagnosed through injecting a small amount of edrophonium hydrochloride (Tensilon), which should improve the ability of the dog to contract his muscles for a short period of time.

There are also other blood tests that can be performed to diagnose MG.

Treatment Options

MG is a manageable disease and dogs that acquire the disease later in life have a favourable prognosis.

Anticholinesteras drugs (i.e. Pyridostigmine bromide) are administrated to dogs with MG. In severe cases of MG, the dog is given neostigmine in injection form or corticosteroids.

It is important to prevent the occurrence of aspiration pneumonia. A dog with MG should get food bowls that at the level of the dog’s mouth, so that he won’t have to bend down, risking to throw up the ingested food. The dog should also remain standing at least 10 minutes after eating, so that all the food is properly swallowed.

The dog must rest more and he shouldn’t perform strenuous activities. Whenever you notice weakness, you should calm your dog down and encourage him to rest.

The dog must be monitored and routine checkups are necessary to prevent any complications.