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.
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