1H magnetic resonance spectroscopy of the lentiform nucleus in primary focal hand dystonia

Focal Hand Dystonia Affecting Musicians. Part I: An Overview Of Epidemiology, PathoPhysiology And Medical Treatments

In 1911, Oppenheim coined the term ‘dystonia’ to describe disordered motor control, characterised by an association of hypotonia and tonic muscle spasm. Focal hand dystonia is one form of this disorder, in which symptoms are often task-specific and occur during skilled movements such as writing (writer's cramp) or playing a musical instrument (musician's cramp). Much research has been conducted on the pathophysiology of dystonia, but the underlying mechanisms still remain unclear. Hypotheseses about functional central nervous system alterations continue to gain more support. Scientific treatment-based publications on focal dystonia are sparse, and progress in evidence-based treatment options are necessary in order to assist this patient group. This paper will review the literature, documenting dystonia classification criteria, manifestations, pathophysiology and medical treatment techniques for musicians affected by focal hand dystonia.

Focal dystonia: current theories

Dystonia is a syndrome characterised by abnormal involuntary sustained muscle contractions that often result in twisted and abnormal positions. Focal dystonia affects only a single body part with symptoms varying from permanent (e.g., torticollis) to task-specific (e.g., musician's cramp). The exact causes of focal dystonia have yet to be determined. Possible causative factors have been identified at all levels along the sensorimotor pathway, including anatomical constraints of the hand (musicians), abnormal co-contractions of the muscles due to reciprocal inhibition in the spinal cord, subcortical and cortical remapping, deficiencies in sensorimotor integration and perceptual deficits. A review of the current literature on these topics is provided with a special focus on musicians with focal dystonia. Also reviewed are current treatments of focal dystonia in musicians. On the basis of the currently available evidence, certain risk factors are identified for the development of task-specific focal dystonia, including number of practice hours, personality, genetic predisposition, performance factors and sensory effects. In addition, it is highlighted that dystonic movements occur predominantly in the context of perceptual-motor tasks involving emotions. When emotional and motor traces have become associated, they are difficult to change; it is suggested that this mechanism plays an important role in the preservation of dystonic symptoms.