Anyone familiar with Masticatory Myositis in dogs?

[FISHER ED]

Friday morning I wake up to take my 2 year old Lab out for some dummy work. Come to find out he can't open his mouth wide enough to get his standard size dummy in his mouth and I can see some pain in his eyes when he tries. I figure his mouth is sore so I grab his puppy dummy and he is all over it for the session. He eats his food like normal so I don't think to much more about it. Get home that evening and now he can't even get the puppy size in his mouth and can't eat or drink. His head is all swollen up around his eye also. I nurse water in him throughout the night with a squirt bottle and our Vet says to bring him Saturday morning.

The Vet immediately thinks it is this Masticatory Myositis but doesn't rule out a trauma to the jaw either. I hate to admit this but my dog is a big baby so I'm pretty sure that if he tweeked his jaw one training session I would have heard about it "yelp". He ends up getting a steroid shot and a RX for some steroid pills and antibiotics. We are given the instructions and told to keep them updated on his condition.

Has anyone gone through or know anyone who's dog has had this in the past? Is it something we can look forward to clearing up for good or will he possibly have some effects from this? It just kills me to see him so down in the mouth. He wants his dummys and bones so bad but just can't do it. The "sad puppy face" is really getting to me and the wife. Thanks.