Four patients, aged 25 to 42 years presented with acute onset of a movement disorder characterized by a tonic, sustained, lateral and outward protrusion of one half of the lower lip. The movement disorder was present at rest, while in some patients, it was also present during speech. In all cases, the abnormal lip posture could be suppressed voluntarily. Neurological examination was otherwise normal. Extensive laboratory investigation failed to reveal any causative factors for secondary focal dystonia. Treatment with oral medications and botulinum toxin was mostly ineffective. Spontaneous remissions were frequent.
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