Myasthenia gravis symptoms can render your dog unable to control his motor function and vulnerable to megaesophagus and the potentially deadly lung infection known as aspiration pneumonia. In a normal dog, nerve endings excrete the neurotransmitter acetylcholine when the dog wants to move; these neurotransmitters find acetylcholine receptors on the corresponding nerve endings, which allows the nerve impulse to travel from the brain to the muscles and initiate movement. Myasthenia gravis hinders this process by reducing the number of acetylcholine receptors in the brain. Here's what you should know.
Causes of Myasthenia Gravis
There are two types of myasthenia gravis. Congential canine myasthenia gravis is genetic and hereditary. Dogs with this form of myasthenia gravis are born without the appropriate number of acetylcholine receptors.
Acquired myasthenia gravis is an autoimmune condition in which the dog's own immune system attacks acetylcholine receptors in the brain, damaging them and stopping nerve impulses from traveling to your dog's muscles as they should.
While myasthenia gravis can affect dogs of all breeds, Miniature Dachshunds, Jack Russel Terriers and Smooth Fox Terriers are among those more susceptible to this condition.
Symptoms of Myasthenia Gravis
Myasthenia gravis often causes muscle weakness in the legs, particularly the hind legs. Dogs with this disorder may have trouble standing or jumping. They may stumble and wobble when they walk. Their legs may tremble, and they may be too weak to perform even light exercise.
In addition, dogs with myasthenia gravis may experience weakness in the muscles of the eyes, throat and face. The disease can cause megaesophagus, an enlargement of the esophagus that can make it hard for your dog to swallow. His voice may change and he may begin regurgitating his food because his swollen esophagus won't allow him to swallow it. Your dog might even lose weight as a result of inadequate nutrition.
Complications of Myasthenia Gravis
One of the most dangerous complications of myasthenia gravis is aspiration pneumonia. Aspiration pneumonia is a lung infection that can occur when your dog inhales a foreign object. Myasthenia gravis can damage the reflex that keeps foreign matter out of your dog's lungs when he swallows, allowing particles food to penetrate your dog's lungs. Aspiration pneumonia can be life threatening and requires immediate treatment.
Treating Myasthenia Gravis in Dogs
Myasthenia gravis in dogs generally responds well to treatment. Your vet can administer drugs to increase the levels of acetylcholine in your dog's brain, enhancing motor control and increasing muscle strength. These drugs will need to be administered by injection. Common drugs for the treatment of myasthenia gravis in dogs include prednisone and other corticosteroids, pyridostigmine and edrophonium chloride.
Many dogs experience remission from myasthenia gravis symptoms. Vets believe that as many as 90% of dogs could eventually spontaneously recover from the symptoms of myasthenia gravis within 18 months of diagnosis. However, dogs in remission are still at risk for a relapse of the disease and may need further treatment for symptoms later in their lives.