Which movement disorder is characterized by involuntary contractions of the neck muscles causing abnormal head posture?

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Spasmodic torticollis is a focal dystonia of the neck, where involuntary, sustained or intermittent contractions of the neck muscles pull the head into abnormal postures such as turning, tilting, or pulling forward/backward. This description matches the stem’s idea of involuntary neck muscle contractions producing an abnormal head position. It’s a classic example of cervical dystonia, involving abnormal muscle tone and movement patterns driven by disrupted motor control circuits, often within the basal ganglia.

In contrast, myoclonus involves brief, shock-like jerks rather than a sustained abnormal posture; tics are repetitive movements that are often suppressible and preceded by an urge, not typically producing a fixed neck posture; akathisia is marked by inner restlessness and pacing or cannot stay still, generally not limited to the neck.