Dystonia is a syndrome characterized by involuntary, sustained, patterned, or repetitive muscle contractions of opposing muscles causing twisting movements or abnormal postures.1 Task, specific dystonia is a form of action, dystonia with non-coordinated movements and involuntary muscle contractions that occurs only at the attempt of performing specific motor tasks (e.g., writer's cramp, task-specific dystonia in piano and tabla players, musicians with embouchure dystonia and praying-induced dystonia).1–7 On a recent paper published by Conti et al.,6 the authors reviewed all published cases of musician's hand dystonia, explored the pathophysiological mechanisms involved, and clinical implications. As many as 8% of musicians may be affected during their careers.6, 7 Many theories were proposed to explain the underlying mechanisms. One of these theories is the abnormal activation of basal ganglia, motor cortices, and cerebellar hemispheres as occurs in patients with writer's cramp2 and the deficiency of homeostatic control of the range of modifiability of sensorimotor circuits as shown by Quartarone et al.2 in cases of writer's cramp using transcranial magnetic stimulation. Finally, recent studies support a dual role for genetic and environmental factors in the development of focal task-specific dystonia of musicians' hand.6
We report an unusual presentation of a task-specific dystonia in a 24-year-old man. The patient started his singing career of Brazilian country music, at the age of 18 years. After live performances, he noticed a significant cervical discomfort. A few months later, he started to present while singing higher frequency notes, left torticollis with mild laterocollis to the same side associated with difficulties to keep the voice normally pitched, always only while singing. When he tried to keep his head on a neutral position his voice changed to a high-pitched, coarse, or strangled tone. The phenomenon did not manifest while singing lower frequency notes as well during normal speech. He denied previous head trauma or any neurological conditions. Neurological examination at rest was normal, but when asked to sing Brazilian country music, he immediately developed left torticollis and a mild left laterocollis with severe right sternocleidomastoid muscle (SCM) hypertrophy (see Video). Laboratory tests and cranial CT scan were normal. Electromyography demonstrated prolonged bursts on the right SCM only when singing.
This patient was diagnosed with a task-specific cervical dystonia. His treatment consisted in intramuscular injections of botulinum toxin type A (BT-A; Dysport, Biosintetica, Sao Paulo, Brazil). In the left splenius capitis (300 IU) and in the right SCM (150 IU).
On follow-up after 3 weeks, the dystonic symptoms and the SCM hypertrophy were significantly improved. Nevertheless, the patient complained that his voice became less powerful after the procedure, and declined subsequent botulinum toxin injections. The patient was re-examined after 6 months and reported that the symptoms returned after the third month, moderately less intense than before treatment.
Task-specific focal dystonia occurs mainly in highly skilled manual tasks, and are usually related to occupation (piano players, architects, writers, and shoemakers). Rare cases were described in oromandibular region (e.g., embouchure dystonia in brass players). There are two reported cases of unusual task-specific dystonia: praying-induced dystonia observed in a Turkish patient who developed slurred speech when reciting Islamic prayers, and a focal dystonia of the jaw developed by an auctioneer, which occurred only during his selling patter and resolved on stopping.2–4, 7 Jankovic and Ashoori7 published an exceptional review of movement disorders in musicians and dystonia appears to be by far the most common.
The present case illustrates an unusual and to the best of our knowledge, never before reported case of task-specific cervical dystonia elicited by the singing act.