[Unexpected clinical diagnosis of myotonia]

We studied all the electromyographic studies carried out in our Service until 1995, in order to quantify the find of myotonia and to compare it with the previous clinical diagnosis that originated the exploration. 30% of the findings of myotonia were unexpected. Non-filiated myopathy and weakness on study, were the principal clinical correlates in those unexpected findings. It must be noted the importance of misdiagnosed myotonia on the epidemiological data of myotonic dystrophy.