Surgical intervention for oromandibular dystonia-related limited mouth opening: Long-term follow-up

BackgroundOromandibular dystonia is a movement disorder that is characterized by involuntary masticatory and/or lingual muscle contracture. Jaw closing dystonia, the most common subtype of this condition, can cause trismus and is frequently misdiagnosed as temporomandibular joint disorder or masticatory muscle tendon-aponeurosis hyperplasia.Materials and methodsThis report describes the long-term results of 18 patients with limited mouth opening (mean maximal mouth opening: 12.2 mm) due to jaw closing dystonia who underwent surgery.ResultsFifteen patients were treated by injecting botulinum toxin (Botox) into their masseter and temporal muscles. The patients' involuntary muscle contractions improved, but the effects were only mild and transitory. Therefore, bilateral coronoidotomy and masseter muscle stripping were performed. The mean maximal jaw opening significantly increased to 28.3 mm under general anesthesia combined with muscle relaxation, and was 47.1 mm after surgery. An analysis based on an objective scoring system detected a mean overall improvement in the patients' symptoms of 80.2%. The mean duration of the follow-up period was 79.4 months. Six patients required additional Botox injections into the masseter and/or medial pterygoid muscles.ConclusionsIt was suggested that coronoidotomy is useful for patients with jaw closing dystonia accompanied by trismus in whom other therapies are ineffective.