Focal hand dystonia in musicians - surgical correction of hand factors as part of treatment in selected cases

 

Hand dystonia in musicians (HDM) is a task-specific hand/finger coordination disorder - occurring in play while the hand generally functions normally in other tasks. The mean age of onset is about 33 years. The causes of HDM are not yet established and HDM is diagnosed solely on the basis of symptoms of task-specific dyscontrol. The disorder limits and often terminates a performing career. Therefore, musicians with HDM are highly motivated to find a solution. However, current medical treatments are generally of limited effectiveness or ineffective.

 

The classical model of HDM presumed a disturbed movement coordination in the central nervous system (CNS) triggered by repetitive motion. Consequently, research generally focused on finding a predisposing substrate in the CNS. While some neurologic abnormalities have been identified, the general sense is that these are only partially responsible, perhaps mostly predisposing rather than completely explanatory. The view now is that HDM has a multifactorial etiology. 

 

It appears that another important factor arises from overcompensation for features that peripherally biomechanically or otherwise interfere with playing motions [see Publications-5]. Examples are anatomical substrates of the arm and hand, congenital or acquired by, for example, trauma, limiting finger independence or otherwise interfering with the playing tasks, nerve compressions diminishing proper activation of muscle, subclinical defects in ligaments affecting joint stability, and similar factors not limiting daily hand use but biomechanically significant to the playing tasks. Such peripheral impediments may also underlie persistent problems with the playing technique. Note that, diagnostically, the distinction between a problem with the playing technique and the early stages of a finger control problem is vague.

 

It is even conceivable that HDM could be triggered within a normal CNS system by such peripheral factors.  In such a situation, the peripheral factor hypothesis implies the possibility of more effective treatments, at least in selected cases. A surgical correction of these factors – if operationally feasible - could create a hand in which HDM would not have occurred, given equal environmental circumstances. In those cases, a surgical correction followed by rehabilitative reduction of the overcompensated motor patterns and retraining of the playing technique making use of the augmented motion possibilities would have a significant greater chance to regain asymptomatic playing skills than conservative treatments where these peripheral factors remain unchanged and active as motion impediments.

 

Certainly, there is no claim that peripheral factors would account for all cases of HDM. The symptoms leading to a diagnosis of HDM vary widely. Different processes may lead to dyscontrol symptoms that, while strongly varying in detail, may have sufficient common characteristics to invite the diagnosis. For instance, small underlying tremor might be a trigger factor of central cause. Also, at a hand clinic for musicians, a HDM case presented in association with an early stage of MS. Hence the importance of a multidisciplinary approach in diagnostics.

 

Therefore, in conclusion, musicians with

• task-specific HDM unresponsive to conservative treatments,
• no systemic conditions that might be associated with the symptoms,

might consider and might possibly benefit from a detailed examination of peripheral factors as enumerated in the above.

 

Biomechanical evaluations – the process

The HBCM offers, as part of a multidisciplinary examination, the possibility of advanced evaluations of physical/anatomic factors as biomechanical playing impediments and of the biomechanically lawful processes of compensatory motion adaptations these factors should induce. Symptomatic playing motions in HDM are generally by no means completely random, but contain residual functionality indicative of the motion compensations preceding the overcompensations. A biomechanical analysis gains causative validity to the degree that the biomechanically lawful compensatory processes associated with the peripheral factors are consistent with the residual functionality in the symptomatic motions.