Facial twitches in ADCY5-associated disease - Myokymia or myoclonus? An electromyography study

Objective A clinical feature in patients with ADCY5 gene mutations are perioral muscle twitches initially described as facial myokymia. Methods Five patients with ADCY5-associated disease with facial twitches and truncal jerks underwent electrophysiological investigations of the orbicularis oris and trapezius muscles to delineate neurophysiological characteristics of these phenomena. Results Electromyography (EMG) recordings showed a complex electrophysiological pattern with brief bursts of less than 100 ms and longer bursts with a duration of 100–300 ms up to several seconds in keeping with myoclonus and chorea, respectively, as key findings. None of the patients had EMG patterns of myokymia. Conclusions In this series of five ADCY5 mutation carriers, perioral twitches and truncal jerks do not represent myokymia. In view of characteristic clinical signs and electrophysiological patterns with a combination of myoclonus and chorea it might be preferable to refer to these phenomena as myoclonus-chorea.