This article includes supplementary video clips, available online at .

mds21488-MDS21488.mpg13196KSegment 1.Dystonic downward deviation of the left labial angle is shown. The maxillary splint is shown. Dystonia subsides when the patient puts the splint on. Needle electromyography shows spontaneous firing of motor unit action potentials (MUAPs), some of them polyphasic, from left depressor anguli oris (or triangularis) muscle, but not from right depressor anguli oris or left orbicularis oris. When the patient wears the splint, the spontaneous firing of MUAPs subsides and disappears.

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.