What is Myasthenia Gravis?

Just an amusing coincidence, before I talk about MG, and what this diagnosis meant for Hobbes and for us.  Today I go to the neurologist for an EMG of my right hand (carpal tunnel syndrome--no longer a work-related injury thanks to Harvard <grrrr>).  Anyway, an EMG consists of sticking needles into my hands to test how my nerves respond--just like they did to poor Hobbes at Cornell!  I'm sure he is feeling vindicated this morning!

Again, I'm not a doctor, so my take on MG will be simplistic at best.  I am obviously more concerned about its impact than I am with the chemical reasons for its occurance.  Acquired MG in a dog is an auto-immune condition.  His body is making antibodies against a chemical that allows his nerves and muscules to communicate.  A dog that is born with MG does not have the necessary receptors that allow this communication to occur.  That means that a dog with acquired MG has these receptors, but exhibits all of the physical characteristics of having MG.  No one knows how dogs acquire MG.  Some believe it has something to do with their innoculations; their bodies have an adverse reaction to their rabies or distemper shots.  While Hobbes did react poorly to his rabies vaccination, no one can say definitively that this shot caused his body to attack itself, resulting in the MG. 

What are the physical signs of a dog with MG?  It will vary from dog to dog, depending on whether the MG is localized or systemmic.  For many it manifests in ME only, meaning that the only muscles affected are those in the esophagus.  For others, ME may not occur, but the dog may exhaust completely after brief periods of exercise, or they may be completely lethargic.  Any muscle group can be affected.  Hobbes' MG, for example, initially was localized in his esophagus.  This may be why the blood test for MG, which looks for those antibodies in the blood, came back negative.  As time passed, however, Hobbes' MG spread to his legs, which is why he would stop walking and had to be carried home.  If you watch Hobbes for any period, you will also notice that his facial muscles are also affected--particularly his eyes.  He blinks a lot, and his eyelids droop, even when he is clearly wide awake.

What does this mean for Hobbes?  As I mentioned earlier, he takes additional medication to manage his MG, administered three times daily, reinforcing the need for Hobbes to have three meals.  We can take him for walks now, but we have to be careful because he still tires easily.  Hobbes will also never have any vaccinations again.  No rabies, bordatella, etc., to prevent further aggravation of the condition.  Of course, that also means that no boarding facility will ever take Hobbes--not that they would anyway.  Otherwise, his daily life is pretty much normal, well, beyond eating in the box.

Hobbes' prognosis is unknown.  Research shows that most dogs with acquired MG will go into remission.  That doesn't mean the ME goes away, but the rest of the muscle weakness abates.  For those dogs that do not go into remission, the same research shows they likely will get some form of cancer.  Hobbes has shown no signs of remission at this point, and he was diagnosed about 6 months ago.  We are still hopeful, though, because remission may occur as much as two years after diagnosis.  What ever happens, we will continue to take care of the little pest as long as he is with us, because we love him.

One final note.  In a previous post I discussed Hobbes hip problems, and our initial concern that he has hip dysplasia.  It is possible that the very loose joints are due to the MG, but we really don't know.  Whether the looseness is caused by MG or HD, however, we still need to be vigilant, because the same damage to the joints will occur.