Primary Cueing Tremor: A Task-Specific Tremor of Billiard Players.

Objective: To describe a unique form of task-specific tremor (TST) in billiards players. Background: Task-specific movement disorders occur during highly learned activities. While task-specific dystonia in billiards players has been reported, TST has not been previously characterized. Methods: Case series with literature review. Cases: Two right-handed billiards professionals developed tremor specifically during cueing. In Case 1, a 55-year-old experienced right arm tremor triggered by shoulder extension during cue positioning. Tremor resolved upon shooting, improved with alcohol, and was confirmed by electromyography showing a 6.3-Hz tremor. Botulinum toxin provided partial benefit, whereas medications were ineffective. Case 2, a 66-year-old player, had coarse tremor in the non-dominant (left) hand used to form the bridge during his shooting stance, contrasting with Case 1, where the dominant hand holding the cue was affected. Medications were ineffective, but thalamic deep brain stimulation resulted in approximately 70% improvement. Both had subtle bilateral postural and kinetic tremor, and neither showed features of dystonia. Conclusion: Our cases expand the phenomenology of task-specific movement disorders in billiards players to include tremor. Alcohol responsiveness and electrophysiologic findings suggest a variant of essential tremor. Recognizing primary cueing tremor may have implications for treatment, natural history, and pathophysiology, which likely differ from those of billiards-related dystonia.