Deep Phenotyping of Musicians' Upper Limb Dystonia

Area of Science:

• Neurology
• Movement Disorders
• Musculoskeletal Disorders

Background:

• Focal task-specific dystonia of the musicians' arm (FTSDma) is a disabling condition impacting musicians' careers.
• The exact causes and best treatments for FTSDma remain poorly understood.

Purpose of the Study:

• To deeply phenotype FTSDma and compare it with writer's cramp (WC) and other arm dystonias.
• To identify distinct clinical patterns within FTSDma and related conditions.

Main Methods:

• Reviewed records and videos of 173 FTSDma patients, 50 WC patients, and 16 with other arm dystonias.
• Utilized "deep phenotyping" through slow-motion video analysis to categorize dystonia.
• Compared clinical findings with literature data on FTSDma, WC, and other dystonias.

Main Results:

• FTSDma typically affects men in their fourth decade, often involving the right hand.
• Identified four categories: precision-grip dystonia, power-grip dystonia, and proximal dystonia.
• Observed similarities between FTSDma in string players/drummers and WC/racquet dystonia, frequently affecting the wrist, forearm, or shoulder.

Conclusions:

• Deep phenotyping highlights shared dystonic phenotypes across different musical instruments due to technical demands.
• Unexpected similarities exist between FTSDma and other forms of task-specific upper extremity dystonia.
• A network model is proposed to explain the observed findings in arm dystonia.