Dystonia limited to the hyoid muscles is an example of focal dystonia.
Hyoid muscles:
(1) digastric
(2) mylohyoid
(3) omohyoid (infrahyoid)
(4) sternohyoid (infrahyoid)
Risk factors:
(1) stress
(2) prolonged use of vocal muscles
(3) history of neuroleptic or illegal drug use
Clinical triad:
(1)
changes in speech resonance
(2) anterior neck tightness
(3) dysphagia
The dystonia may be limited to the hyoid muscles or in combination with cranial and/or cervical dystonias.
Physical exam shows contraction of the hyoid muscles with abnormal positioning of the larynx or chin.
The diagnosis is supported by improvement after injection of botulinum toxin (into anterior belly of digastric muscle, mylohyoid, other).
