Chewing pattern in patients with Meige's syndrome.

Meige's syndrome presents with a combination of upper and lower facial motor dysfunction, including eye closing spasms and oromandibular dystonia. While the pathophysiology of eye closing spasms has been extensively studied using the blink reflex and other trigeminofacial reflexes, very few studies have been carried out with regard to the abnormal perioral movements. We hypothesized that action-related dystonic features could be revealed by the analysis of the semiautomatic rhythmic movements required for chewing and swallowing. A total of 7 patients with Meige's syndrome that complained of chewing problems and 7 age-matched healthy volunteers were studied. Subjects were instructed to munch and swallow a small muffin while surface electromyographic (EMG) activity of masseter (MAS) and orbicularis oris (OOr) of the dominant side was recorded. In healthy subjects, MAS and OOr showed a rhythmic alternating phasic EMG pattern during chewing, which changed to a tonic cocontraction of both muscles during swallowing. Mean duration of MAS and OOr EMG bursts was, respectively, 297 +/- 28 msec and 328 +/- 29 msec. Patients exhibited the following alterations: excess duration of muscle activity, frequent cocontraction, loss of rhythmicity during chewing, and abnormalities in the chewing to swallowing transition phase. These abnormalities, similar in type to those encountered in other forms of focal dystonia, may be the expression of an abnormal motor control of basal ganglia over mastication-related movement pattern generators of the brainstem. (c) 2004 Movement Disorder Society.