Myasthenia gravis affects the communication between nerves and muscles. In a healthy dog, neurons (cells) and axons combine and connect the spinal cord to many muscles within the body. The brain sends a chemical message (acetylcholine) to the spinal cord and neurons in order to prompt a muscle to react a certain way.
After the “message” is received and performed, the body sends out an enzyme that dissolves the acetylcholine called acetylcholinesterase. This process slows and stops muscle movement. In dogs with this neuromuscular disease, the messages get messed up leading to involuntary or weakened muscle movements.
Symptoms are generally noticeable with muscle weakness of the face, throat and limbs. Many dogs with the disease tire easily when exercising and have difficulty swallowing food or water. When the disease weakens the esophagus muscle, food aspiration pneumonia becomes a potential risk. It's best to seek veterinary advice as soon as possible.
Types of Myasthenia Gravis
In order to treat the disease, it's important to determine which form of the disease is affecting your pet. There are two forms:
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Acquired Myasthenia Gravis is a disease where the immune system attacks the neuromuscular junctions. The only way to stop the disease is by taking medications that suppress the immune system. It's most commonly seen in adult dogs. German Shepherds and Labradors are susceptible to this form of the disease.
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Congenital Myasthenia Gravis occurs when a puppy is born without healthy connections between the nerves and muscles. It's more common in Dachshunds, Fox Terriers, Jack Russells and Springer Spaniels. The condition may disappear as the puppy ages.
Veterinarians frequently test for the disease by giving an injection of Tensilon and then seeing if the muscle response improves for a short period of time. If it does, this is a key indication that the dog does have the neuromuscular disease.
Treatment Plans for Myasthenia Gravis
Many dogs never require treatment for this nerve disease. It simply goes into remission after 6 to 18 months. Those dogs that do not go into remission ended up with cancer within a few years of the initial diagnosis. This is why it is important to discuss treatment plans with your veterinarian if your dog show no signs of improvement.
Reduce the risk of aspiration pneumonia by taking your dog for a walk after eating. Eating from an elevated food bowl can also help. Try to keep your dog standing for at least 10 minutes following a meal to ensure all food makes it down the esophagus into the stomach rather than into the lungs.
Medications to extend the function of acetylcholine are recommended in the autoimmune form of the disease. Medications like Mestinon prevent acetylcholinesterase from destroying the acetylcholine. The medication is given two or three times a day. Key side effects are excessive drooling and nausea. Giving the medication with food can help alleviate the nausea.
Corticosteroids are used if Mestinon isn't effective. Because there are may side effects and precautions to using corticosteroids, they should be considered a last resort. Dogs with diabetes and high blood pressure must avoid corticosteroid treatments.