Movement disorders of the stomatognathic system: A blind spot between dentistry and medicine

Movement disorders of the stomatognathic system include oromandibular dystonia (OMD), oral dyskinesia, sleep/awake bruxism, functional (psychogenic) stomatognathic movement disorders (FSMDs), tremors, and hemimasticatory spasm (HMS). Most patients first consult dentists or oral surgeons. The differential diagnoses of these involuntary movements require both neurological and dental knowledge and experience, and some of these movement disorders are likely to be diagnosed as bruxism or temporomandibular disorders (TMDs) by dental professionals. However, excepting movement disorder specialists, neurologists may find it difficult to differentially diagnose these disorders. Patients may visit numerous medical and dental specialties for several years until a diagnosis is made. Therefore, movement disorders of the oral region may represent a blind spot between dentistry and medicine.The present narrative review aimed to describe the clinical characteristics and differential diagnoses of some movement disorders, as well as the problems bridging dentistry and medicine. Movement disorders have the following characteristic clinical features: OMD - task specificity, sensory tricks and the morning benefit; FSMDs - inconsistent and incongruous symptoms, spreading to multiple sites and the lack of sensory tricks; and HMS - the paroxysmal contraction of unilateral jaw-closing muscles, the persistence of symptoms during sleep and the loss of a silent period. A careful differential diagnosis is essential for the adequate and effective treatment of each involuntary movement. Refining the latest definition of bruxism may be necessary to prevent the misdiagnosis of involuntary movements as bruxism.Both dental and medical professionals should take an interest in the movement disorders of the stomatognathic system, and these disorders should be diagnosed and treated by a multidisciplinary team.