Hyoid muscle dystonia: A distinct focal dystonia syndrome

Introduction: Adult-onset dystonias are often segmental in distribution and preferentially affect the craniocervical muscles. Here we describe an overlooked muscle group involved in craniocervical dystonia - the hyoid muscles. Dystonia of these muscles results in anterior neck tightness, speech changes, and dysphagia. Methods: For this retrospective study we obtained a list of 55 patients who had received botulinum toxin injections into hyoid muscles between 1998 and 2013. Fifteen patients were identified to have an unusual dystonia affecting the hyoid muscles. Results: Patients presented with a triad of speech resonance changes (100%), anterior neck tightness (86.6%), and dysphagia (73.3%). Ten (66.7%) patients presented with all three symptoms, while fourteen (93.3%) had at least two. Fourteen patients (93.3%) had a concomitant dystonia affecting the face or neck and eleven (73.3%) had a sensory trick. Exam universally showed contracted hyoid muscles. Some patients had professions or hobbies requiring prolonged use of vocal muscles such as teachers, singers, and musicians. Patients were often misdiagnosed and received unnecessary treatments. Patients underwent botulinum toxin injections into various hyoid muscles with benefit in 71% of patients but adverse effects in the same proportion. Conclusions: Hyoid muscle dystonia is a previously poorly characterized focal dystonia causing the triad of speech changes, anterior neck tightness, and dysphagia. Concomitant dystonia, sensory tricks, and visualization of contracted hyoid muscles were often present. Recognition of this disease may reduce unnecessary testing and treatments, and patients may benefit from botulinum toxin injections.