Yes, we all have myotonic discharges in every skeletal muscle. You can't diagnose MC from an EMG alone because there are several conditions that show up that way on the test. They used to look at family history and pattern of inheritance, and sometimes even do a muscle biopsy, to try to make an educated guess, but now that we have DNA testing that's not necessary.
Hi Jan, thanks for the reply.. What if you do testing for myotonia congenita and they come back with nothing ?are there some types that there are no DNA test for ? I didn't have any blood work yet and I am worried..
If you are tested for the chloride channel myotonias (Thomsen and Becker MC), the sodium channel myotonias (Paramyotonia, potassium aggravated myotonia/acetazolamide responsive myotonia, periodic paralysis), and muscular dystrophy type I and type II, and everything comes back negative, then there are a few possibilities.
1. Sometimes, for one reason or another, they fail to detect an existing mutation or defect on a gene. I think this is more common with sodium channel myotonias.
2. You have a mutation on a gene relating to muscle function, which was not sequenced. This could be the gene that codes for potassium channels, or maybe even calcium channels within the muscles.
3. You have some other condition which causes a phenomena similar to myotonia. For example, thyroid problems, Isaac's Syndrome.
I wouldn't worry too much though. It's not often that they don't find the cause once they know what to look for.