Focal dystonia

Original Editor - Carlos Areia

Top Contributors - Carlos Areia, Kim Jackson, Laura Ritchie, Evan Thomas, Anas Mohamed, Aminat Abolade, Admin, Wendy Walker, Tarina van der Stockt, WikiSysop, Vidya Acharya, Scott Buxton and Naomi O'Reilly

Introduction

Dystonia is defined as an involuntary contraction of the agonistic and antagonistic muscles, which can lead to repetitive involuntary movements and/or abnormal positions, most common in the hand (known as Focal Hand Dystonia). The affected population includes individuals who require repetitive movements on their regular daily life; one of the most affected populations are the musicians and professional writers . In the European and American population Focal dystonia varies its prevalence between 3 and 29.5 per 100.000 inhabitants . Inside musicians dystonia it is estimated that of all musicans, 0.5 % to 1% suffer from some form of focal dystonia . This figures are highly variables if we individualize each case, depending on the instrument and the effort required on each performance; for instance the difference between a rhythm and a soloist guitar player.

Mechanism of Injury / Pathological Process

Although the pathological process of Focal Dystonia is still classified as idiopathic, increasing evidence suggested a multifactorial etiology (e.g.  interaction between genetic, neuromuscular, auditory, neural adaptative, anatomic, stressful, repetitive, psychosocial, traumatic, among others). An alteration in tactile discrimation was found in dystonic musicians comparing with generalized dystonias and healthy controls; this has been related with the superposition of the areas of representation of the fingers affected in musicians . Other etiological mechanisms are also described in further literature, for instance the alteration of inhibitory spinal, trunk, and intracortical  and alterations in sensorimotor integration. 

Many triggering factors have been described in current evidence, we can distinguish them as external and internal triggering factors, among the extrinsic some examples are the spatial, temporal and spatial contraints depending on the workload of the respective body part and the complexity of the movements used; for intrinsic triggering factors have been described the need of control, the need of perfectionism and anxiety, local pain, trauma, overuse and the deficit in inhibitory mechanisms; also predisposition factors have been considered such as genetics and sex; these triggering factors combined can affect the manifestation of Dystonia.

Clinical Presentation

Some examples of Focal dystonia are Cervical Dystonia, Musician's Dystonia, Writer's Dystonia, Spasmodic Dystonia, among others. Only Musicians and Writers Dystonia are going to be referenced.

Musician's Dystonia is manifested by a loss of voluntary motor movement in repeatedly trained movements, this is a high disabling pathology that can end a musical career; it can be classified according to the instrument played and the movement extensively performed, normally it occurs without pain although aching as been described after prolonged spasms. This loss of muscles coordination is often accompannied by a co-contraction of the antagonist ones.

Writer's Dystonia or Writer's cramp can be also be manifested by uncontrollable muscle contractions and abnormal postures of the whole upper limb during writing, also tremor and spasms of the hand can occur.

Diagnostic Procedures

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Outcome Measures

Motor control and ADL scales

Management / Interventions

• Botulin Toxin 
• Surgery 
• Ergonomic changes at the instrument (Musician's dystonia)
• Immobilization 
• Behavioral training 
  

Physiotherapy:

• -TENS 
• -Sensomotor Training 
• -Muscle Strengthening
• -Stretching
• -Relaxation Techniques
• -Home exercises 

Differential Diagnosis

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References

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