I have no experience with Myasthenia Gravis patient but i came across an article, that said the following exercises could be performed. Neck exercise might include variations of the shoulder shrug using hand weights. You could also perform the dumbbell shrug by standing and placing the feet shoulder-width apart with knees slightly bent. Then carry weights in each hand With arms hanging at sides, move the shoulders upward. Hold the shrug for one count and repeat the exercise eight to 12 times.