Masticatory muscle hyperactivity in temporomandibular disorders: is it an extrapyramidally expressed disorder?

Masticatory muscle hyperactivity appears to have an important role in temporomandibular disorders. A pathophysiological model for masticatory muscle hyperactivity is proposed that is centrally mediated, yet maintains support for present peripheral causes and therapies. In this hypothesis, masticatory muscle hyperactivity represents a mild extrapyramidal disorder distantly related to orofacial dyskinesias. Experimental evidence suggests a neurotransmitter imbalance in the basal ganglia, involving dopaminergic preponderance, or cholinergic and GABA-nergic hypofunction as the underlying cause.