[Case of oromandibular dystonia presenting with severe impairment of mouth-opening, and a marked effect by administration of baclofen].

We report a 67-year-old woman with idiopathic oromandibular dystonia (OMD). She could neither open the mouth nor take meals due to involuntarily strong mouth-closing. The movement of face, pharynx and tongue were normal, and she could open the mouth slightly when jaw and cheek were touched (sensory trick). Chvostek sign and Trousseau sign were negative, and opisthotonus was not recognized. The laboratory data including calcium, phosphorous and cerebrospinal fluid were within normal limits, head and cervical MRI, temporomandibular joints-Xp and needle electromyography were normal. The surface electromyography revealed that masseter and chin muscles contracted synchronously. This result meant dystonia around the mouth. The clinical course and physical examination did not support the diagnosis of tetanus, tetany or bulldog response. She was diagnosed as OMD. She had peroral administration of baclofen, because this drug is a GABA-derivative and acts as a muscular relaxant. Her clinical symptoms and dystonic pattern on the surface electromyography improved markedly after the administration. Baclofen is an effective drug for treatment of oromandibular dystonia.