The following information may help to address your question:
Myotonia is usually mild and rarely requires treatment. Routine exercise appears to help with pain control, as well as with muscle strength and endurance. The effectiveness of most medications for pain management varies. Mexilitene, which is very effective for some forms of myotonia, has helped control muscle pain in some people with this condition. Other medications that have been used with some success include gabapentin, nonsteroidal anti-inflammatory drugs (NSAIDS), low-dose thyroid replacement, low-dose steroids, and tricyclic antidepressants. Cholesterol-lowering medications should be avoided when they are associated with increased weakness.
There are steps a person can take to prevent some secondary complications. Anesthetic risk may be increased, so careful assessment of heart and respiratory function before and after surgery are recommended. Affected people should also have a yearly electrocardiogram or cardiac MRI to detect possible conduction defects or cardiomyopathy.
You can see more detailed information about the management of myotonic dystrophy type 2 on the GeneReviews Web site.