Peter, are you sure it wasn't paramyotonia congenita? That is a different ion channel disorder and can cause more weakness. It could also explain why the mexiletine isn't affecting you much.

Myotonia congenita is usually fairly symmetrical, so if you did feel some weakness, it would probably be pretty equal on both sides. Were you ever in an accident that injured your back? That would be a more likely reason for you to have the weakness in one leg. Also lesions in your brain or spine from viral infections in the past can do that. If you haven't already done so, I would ask your neurologist to do an MRI to see if there are some herniated discs that might be causing the problem.

Jan

Type of Myotonia: Thomsen's

Country: USA