I experience a lot of back pain due to a herniated disk. I've been told the pain is NOT from the rupture but rather from my back muscles having to work extra hard to keep my spine 'in line.' The extra work causes muscles spasms, which are painful. My pain significantly decreased when I started Mestinon. I assume this is because my back muscles were then more able to do their job. The pain in my case is not from MG itself but from a kind of complication of MG, i.e. weak muscles. I hope this makes sense.