Sternocleidomastoid muscle hypertrophy in cervical dystonia

During a hospitalization for sepsis in the setting of a urinary tract infection, a 69-year-old man with idiopathic Parkinson disease (PD) developed severe, sudden-onset left-sided neck pain an hour after receiving quetiapine to treat hospital delirium, raising concern for acute dystonic reaction. On review of the patient's history, he had received single doses of haloperidol and quetiapine 1 week and 3 days prior, respectively, without documented dystonic reaction. He had a history of dystonia in his right foot, which was well controlled with botulinum toxin injections. On examination, his head was rotated toward the right with impressive sternocleidomastoid muscle hypertrophy, confirmed by imaging and representing previously unrecognized chronic torticollis. His acute pain improved with antihistamines, and he was scheduled for botulinum toxin injection. Individuals with PD may develop dystonia as a consequence of disease progression with exacerbations during off-periods and with medications such as antipsychotics, although early, prominent dystonia is atypical and would suggest other parkinsonian disorders.¹ Although there are case reports of quetiapine-induced cervical dystonia, rates overall are similar to placebo in the general population. Notably, a previous history of dystonia does increase the risk of a medication-induced dystonic reaction (figure).²

Figure. View and scan of the patient's neck.

View of the patient's right (A) and left (B) neck showing contraction and significant hypertrophy of the left sternocleidomastoid muscle (arrow) and mild enlargement of the right splenius capitis and cervicis muscles. CT of the neck in coronal (C) and axial (D) views shows left head tilt and enlargement of the left sternocleidomastoid (arrows).

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