Focal dystonia

Focal dystonia is a form of dystonia and is a neurological condition 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 high level musicians, focal hand dystonia is referred to as musician's dystonia and focal dystonia in sports is commonly referred to as (the) yips. It is believed that all adult onset dystonias are a product of combined genetic factors and environmental modifiers.

Causes
The cause of dystonia is not precisely understood. Misfiring of neurons in the sensorimotor cortex, a thin layer of neural tissue covering the brain, is thought to cause contractions. The source of this misfiring may be a result of 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. In dystonia, it appears that the ability of the brain to inhibit the surrounding muscles is impaired leading to loss of selectivity.

Furthermore, 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 may cause pain. Focal dystonia most typically affects those who rely on fine motor skills (musicians, writers, surgeons, etc.) and it is thought that the excessive motor training in these individuals 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.

Notable cases
Musicians affected by focal dystonia include Leon Fleisher, of the Peabody Conservatory of Music, who had suffered from this affliction in his right hand, as did Alex Klein, formerly the first oboist of the Chicago Symphony, Ernestine Whitman, former member of the Atlanta Symphony and currently a professor of flute at Lawrence University, pianist and keyboard player Keith Emerson, guitarist Dominic Frasca, and the pianist Gary Graffman, who performs exclusively with his left hand. In 2005, New Age acoustic guitarist Billy McLaughlin announced via his website that he is suffering from focal dystonia, which severely limits his ability to play right-handed (and as a result, he taught himself to play left-handed). British-Canadian Classical Guitarist Liona Boyd had to give up her professional career as Canada's "First Lady of the Guitar" due to focal dystonia that drastically affected her right hand. Bass guitarist, Andy Billups, who plays with British rock act The Hamsters, has also made a partial recovery from this disorder and continued to play by using modified guitar plectrums to make up for the limited function of his right hand. Classical guitarist David Leisner has recovered the full use of his hand and has returned successfully to the concert stage and recording studio in the early 1990s after a decade of disability. Brazilian singer-guitarist Badi Assad was diagnosed with focal dystonia in 1999 (after having been misdiagnosed with carpal tunnel syndrome). She eventually recovered and was able to resume her career. Tom Adams, a professional bluegrass banjo player, has focal dystonia in his right hand, had to give up playing banjo, and now plays the guitar. Scott Adams, the writer of the Dilbert comics, is also afflicted with focal dystonia of the hand, which impedes his artwork. World champion bagpiper Stuart Cassells, founder of the bagpipe rock group Red Hot Chilli Pipers, announced that he had focal dystonia in the group's blog on 23 September 2011, and left the band because it affected his ability to play. Bass player and instructor Scott Devine discovered that wearing gloves while playing his instrument provides an efficacious workaround to the symptoms of focal dystonia.

Treatment
This condition is often treated with injections of botox, a commercially prepared form of botulinum toxin. Botox, however, merely targets the symptoms of the disorder and is not a cure for dystonia. Since the root of the problem is neurological, it is thought that sensorimotor retraining activities can enable the brain to "rewire" itself in a manner that can ultimately eliminate dystonic movements. The work of several doctors as Nancy Byl and Joaquin Farias, has shown that sensorimotor retraining activities and proprioceptive stimulation can induce neuroplasticity, making it possible to recover substantial function that was lost from focal dystonia.