Focal dystonia is a neurological condition, a type of dystonia, that affects a muscle or group of muscles in a specific part of the body, causing involuntary muscular contractions and abnormal postures. For example, in focal hand dystonia, the fingers either curl into the palm or extend outward without control. In musicians, the condition is called musician's focal dystonia, or simply, musician's dystonia. In sports, it may be involved in what is commonly referred to as the yips.
Current medical science does not precisely describe the causes of dystonia. Misfiring of neurons in the sensorimotor cortex, a thin layer of neural tissue that covers the brain, is thought to cause contractions. This misfiring may result from impaired inhibitory mechanisms during muscle contraction. When the brain tells a given muscle to contract, it simultaneously silences muscles that would oppose the intended movement. It appears that dystonia interferes with the brain's ability to inhibit those surrounding muscles, leading to loss of selectivity.
The sensorimotor cortex is organized as discrete "maps" of the human body. Under normal conditions, each body part (such as individual fingers) occupies a distinct area on these cortical maps. In dystonia, these maps lose their distinct borders and overlap occurs. Exploration of this initially involved over-training particular finger movements in non-human primates, which resulted in the development of focal hand dystonia. Examination of the primary somatosensory cortex in the trained animals showed grossly distorted representations of the maps pertaining to the fingers when compared to the untrained animals. Additionally, these maps in the dystonic animals had lost the distinct borders that were noted in the untrained animals.
Imaging studies in humans with focal dystonia have confirmed this finding. Also, synchronous afferent stimulation of peripheral muscles induces organizational changes in motor representations, characterized both by an increase in map size of stimulated muscles and a reduction in map separation, as assessed using transcranial magnetic stimulation.
The cross-connectivity between areas that are normally segregated in the sensory cortex may prevent normal sensorimotor feedback and so contribute to the observed co-contraction of antagonist muscle groups, and inappropriately timed and sequenced movements that underlie the symptoms of focal dystonia. It is hypothesized that a deficit in inhibition caused by a genetically mediated loss of inhibitory interneurons may be the underlying cause of the deficits observed in dystonia.
While usually painless, in some instances the sustained contraction and abnormal posturing in dystonia cause pain. Focal dystonia most typically affects people who rely on fine motor skills—musicians, writers, surgeons, etc. It is thought that the excessive motor training those skills require may contribute to the development of dystonia as their cortical maps become enlarged and begin to overlap. Focal dystonia is generally "task-specific," meaning that it is only problematic during certain activities.
This condition is often treated with injections of botulinum neurotoxin A (BoNT/A). BoNT/A reduces the symptoms of the disorder but it is not a cure for dystonia. Since the root of the problem is neurological, doctors have explored sensorimotor retraining activities to enable the brain to "rewire" itself and eliminate dystonic movements. The work of several doctors such as Nancy Byl and Joaquin Farias has shown that sensorimotor retraining activities and proprioceptive stimulation can induce neuroplasticity, making it possible for patients to recover substantial function that was lost to focal dystonia.
Bass guitarist and instructor Scott Devine said that he wears a glove while playing bass guitar because of the condition. He finds that the glove stops the involuntary finger movements. He says it works for him but does not suggest that it may work for everyone with the condition. 
- Victor Wooten, bassist, suffers from it on both hands
- Scott Adams, the writer of the Dilbert comics, has focal dystonia of the right hand, which impedes his artwork.
- Tom Adams, bluegrass banjo player, has focal dystonia in his right hand, and has switched to the guitar.
- Badi Assad, Brazilian singer-guitarist, was diagnosed with focal dystonia in 1999; she eventually recovered and resumed her career.
- Andy Billups, bass guitarist with British rock group, The Hamsters, has made a partial recovery; he plays by using modified guitar plectrums.
- Liona Boyd, Canadian classical guitarist, publicized as the "First Lady of the Guitar", retired from the concert stage for six years in 2003, due to focal dystonia that affected her right hand. She worked to retrain her right hand, and since 2009 has been performing again as a guitarist, singer, and songwriter.
- Stuart Cassells, founder of the bagpipe rock group Red Hot Chilli Pipers, announced focal dystonia in September 2011; he has left the band.
- Andrew Dawes, noted violinist and co-founder of the Orford String Quartet.
- Keith Emerson, pianist and keyboard player
- Leon Fleisher, an international concert pianist, dealt with this condition in his right hand beginning in the 1960s and switched to only left hand playing. In the 2000s, he regained use of his right hand and recommenced performing and recording with two hands.
- Dominic Frasca, Guitarist
- Gary Graffman, pianist, who changed to performing only with his left hand.
- Jang Jae-in, Korean singer-songwriter and guitarist diagnosed with dystonia in her left hand in 2012. In 2015 in You Hee-yeol's Sketchbook she announced that she quit playing guitar.
- Alex Klein, principal oboist of the Chicago Symphony Orchestra
- David Leisner, classical guitarist, has recovered the full use of his hand after a decade of disability. 
- Billy McLaughlin, guitarist, switched to playing left-handed when afflicted with dystonia.
- Christian Münzner, ex-lead guitar of progressive extreme metal band Obscura
- Apostolos Paraskevas, Greek-American classical guitarist-composer, was struck by focal dystonia to his right hand in 2009. He fully recovered in 2013 after 7,000 hours of personal work in re-constructing his technique. He was able to decode the condition as an unconscious behavioral habit and returned to performing professionally again. His rehabilitation was based on reducing tension in his hand and retraining his brain through proper, relaxed hand movements, practiced extensively. His article A Classical Guitarist's Story of Recovery from Focal Dystonia will be published in London on the Classical Guitar Magazine
- Charlie Parr, American country blues musician from Minnesota 
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- TEDx Talk. Federico Bitti. Cervical Dystonia. Rewiring the brain through dance. https://www.youtube.com/watch?v=DwkHK3rfKO0
- TEDx Talk . Joaquin Farias. Dystonia. Your movement can heal your brain. https://www.youtube.com/watch?v=czW-xBvDtHY
- Glove and Mail. Choosing music over meds, one man's quest to retrain his brain to overcome dystonia. https://www.youtube.com/watch?v=IpcXkV_ex8Y
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