Pathophysiological mechanisms of oromandibular dystonia

Oromandibular dystonia (OMD) is a rare form of focal idiopathic dystonia. OMD was clinically identified at the beginning of the 20th century, and the main clinical features have been progressively described over the years. However, OMD has several peculiarities that still remain unexplained, including the high rate of oral trauma, which is often related to the onset of motor symptoms. The purpose of this paper was to formulate a hypothesis regarding the pathophysiology of OMD, starting from the neuroanatomical basis of the masticatory and facial systems and highlighting the features that differentiate this condition from other forms of focal idiopathic dystonia. We provide a brief review of the clinical and etiological features of OMD as well as neurophysiological and neuroimaging findings obtained from studies in patients with OMD. We discuss possible pathophysiological mechanisms underlying OMD and suggest that abnormalities in sensory input processing may play a prominent role in OMD pathophysiology, possibly triggering a cascade of events that results in sensorimotor cortex network dysfunction. Finally, we identify open questions that future studies should address, including the effect of abnormal sensory input processing and oral trauma on the peculiar neurophysiological abnormalities observed in OMD.Highlights1) Oromandibular dystonia (OMD) differs from other forms of focal idiopathic dystonia.2) Masticatory and facial systems have some peculiar neuroanatomical and physiological features.3) Abnormal processing of somatosensory inputs possibly plays a prominent role in the pathophysiology of OMD.