Myasthenia Gravis in Dogs

Myasthenia gravis is a condition that affects the nerves that help the muscles work properly. The impulses from the dog’s nerves are unable to properly transmit to the muscles, thus causing the muscles to not be able to contract. The dog then becomes overly weakened due to the muscles not working in a proper manner. 

Myasthenia gravis affects dogs, cats, and humans and all of the symptoms and causes are quite similar among the three. Nerves transmit signals to the muscles in order for them to respond properly and do their jobs for the body. When the transmission of these impulses doesn’t make it to the muscles effectively and precisely, then the muscles do not respond. This condition can be quite debilitating to the dog both physically and mentally. 

Congenital myasthenia gravis can affect dogs in the age range of six to eight weeks, and acquired myasthenia can affect dogs of one to four years and nine to thirteen years. The main sign is esophageal weakness as well as weakness of the muscles in the face in both types. Other areas of the body may also be highly affected due to the inability of the groups of muscles to respond to the abnormality in signals from the nerves.

Myasthenia gravis in dogs is a condition where the muscles are very weak due to the inability of nerve impulses to reach them.

Symptoms of myasthenia gravis are very similar whether this condition is congenital or acquired. Symptoms may include:

• Enlarged esophagus due to muscle weakness
• Difficulty swallowing
• Regurgitation
• Inability to move for long periods of time
• Inability to walk properly
• Falling
• Overall weakness
• The desire to rest rather than move around and exercise

Types

There are two main types of Myasthenia gravis disorder. Both of the following types can affect dogs, cats, and humans. The types of Myasthenia gravis are:

• Congenital - A hereditary condition in which there is an insufficient amount of ACh receptors upon the membrane which receives impulse signals
• Acquired - results from antibodies that destroy the ACh receptors

Causes of myasthenia gravis have been researched throughout the years by medical professionals of animals and people. Specific causes include:

• A breakdown of the transfer of nerve impulses to the muscles of the dog
• A deficiency of acetylcholine which transmits from the postsynaptic membrane to the muscles
• A congenital defect which some specific dog breeds are born with
• An acquired, or immune-mediated, disorder where the antibodies destroy the receptors

If your dog is showing signs of muscle weakness and is unable to move properly, make an appointment with your veterinarian. Once you arrive at the veterinarian’s office, he will ask for information about his symptoms, the severity of symptoms, and when you noticed anything different about your dog. He will then perform a complete examination with blood work, urinalysis, and biochemistry profile.

Your veterinarian may perform a test known as pharmacological testing. He will administer a dosage of edrophonium chloride through an IV to check the response of the muscles. Known also as a tensilon response test, it is a widely recommended procedure to test for myasthenia gravis. Although a positive test may not mean a positive diagnosis, it is highly possible with a positive test that your dog has myasthenia gravis.

Your veterinarian may also decide to perform immunological testing, which is a test that will determine the presence of anti ACh receptors, which is typically not present in dogs with this condition. A biopsy of muscle tissue may also be tested to check for any decrease numbers of the receptors.

Another test that may be performed is electrodiagnostic testing. This procedure records muscle action when it is stimulated by electric waves of up to 10 Hertz. If the muscles have a decline in response, this may be another clue that your dog has myasthenia gravis. Once your dog has been diagnosed with this condition, your veterinarian will provide the best treatment plan possible for your loved one.

There are a few treatment options for myasthenia gravis, and your veterinarian will discuss each in detail with you once your dog has been diagnosed. Treatment methods include:

Support with Nutrition

You can adjust the feeding dishes so your dog doesn’t have to bend down so far to eat or drink. Once he eats, it is important to hold him with his head up for at least 20 minutes so he doesn’t become aspirated. Supporting him while he is eating is very important so he can continue to get proper nutrition with this condition. Some dogs with myasthenia gravis need to have a gastrostomy tube placed in order for them to continue to get the nutrition they need. 

Fluids

It is important to prevent aspiration and the pneumonia which can follow in dogs with this disorder. If your dog already has aspiration pneumonia, treatment methods such as antibiotics, a nebulizer, and percussion therapy can be performed to expel the mucus from the lungs.

Respiratory System Support

In severe cases of dogs that have pneumonia, placement in intensive care on a ventilator may be what the veterinarian needs to do in order for your dog to recover.

Medications

There are medications that are used to help with the motility of the esophagus and surrounding muscles. Drugs such as metoclopramide, cisapride, and ranitidine can help the muscles of the esophagus and the surrounding system work more effectively.

Specific Therapies

Depending on your dog’s condition and the severity of the muscle weakness, targeted therapies may be performed in order to help your dog gain mobility. There are many different types of therapies, and the type used is dependent on your dog’s condition. Therapies to increase neuromuscular transmission, immunosuppressive therapies, and glucocorticoid therapies may be considered for your loved one.

While your dog is undergoing treatment, the veterinarian will continue to do physical examinations to see if the therapies are working properly. It will be important to monitor your dog’s progress and any responses to the treatment he is receiving. He may continue to perform the proper tests to check for the status of his myasthenia gravis.

Once your dog is able to go home (if he was hospitalized due to pneumonia), your veterinarian will provide you with the information you need in order to help in his recovery. More than likely, your dog will require therapy from a licensed therapist. 

Several different types of therapies may be attempted in order to see any progress. Your veterinarian will remain in contact with you to note any progress your dog is making. If your dog is enrolled in a specific type of therapy, his prognosis is fair to good, as long as you remain proactive and educate yourself about this disorder. It is important to understand what you need to watch for in terms of new symptoms that may develop. Many dogs with myasthenia gravis continue to live and cope with this disorder. Prevention of aspiration pneumonia is the key to keeping your dog healthy.