Oromandibular dystonia (OMD) is a form of focal dystonia that involves masticatory, lower facial, labial, and lingual musculature. The term “cranial dystonia” is used when OMD occurs in association with blepharospasm. This particular combination is often referred to as Meige's syndrome (for reviews see Bhidayasiri et al. [2006]).

Epidemiology, clinical features, and etiology

Oromandibular dystonia affects women more frequently than men and the prevalence was estimated to be 68.9 cases per 1 million Americans (for reviews see Bhidayasiri et al. [2006]). The range of mean age at onset varies from 50 to 60 years. The involvement of masticatory muscles in OMD may cause jaw-closing or -opening, lateral deviation, protrusion, retraction, or a combination. These movements often result in involuntary biting of the tongue, cheek, or lips and difficulty with speaking and chewing. Its appearance is often socially embarrassing and disfiguring. In patients with jaw-closing OMD, dystonic spasms of the temporalis and masseter muscles may result in clenching or trismus and grinding of the teeth or bruxism. On the other hand, the lateral pterygoids, anterior belly of the digastric muscle, and other submental muscles are commonly involved in jaw-opening dystonia, and contractions of these muscles may lead to some degree of anterocollis. Oromandibular dystonia may be alleviated by different proprioceptive sensory inputs (“sensory trick”). These include touching the lips or chin, chewing gum, or biting on a toothpick. A recent study demonstrated that coexistence with dystonia in other regions and presence of sensory tricks are more common in jaw-opening than jaw-closing OMD.