Try to think positively! A good neurologist will easily be able to see the signs of MG. I hope the experience will be good. There are now 3 different MG antibodies: AChR, MuSK, and LRP4. There might be more they haven't discovered yet. This neuro may want to redo the AChR antibodies (experts often do).
MG is considered a "head and down" disease. Symptoms often show up in the head/neck/face area first. One of my first symptoms, besides ptosis, was the back of my neck feeling like a vice grip after I talked or laughed too much. There are a lot of muscles in that area too! 640 skeletal muscles in the human body that MG can affect.
MG is all about weakness that fluctuates. A good neuro can easily fatigue the muscles of someone with MG during a good clinical exam.
Please let us know how you're doing. Good luck with the appt!

Annie