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Focal dystonia and ulnaropathy in musicians

Page 1 of 4

Boni Rietveld
orthopaedic surgeon
Medical Centre for Dancers and Musicians, MCH, loc.Westeinde Ziekenhuis, The Hague, Netherlands

Definition, classification and diagnosis of focal dystonia in musicians:

Dystonia is defined as involuntary spasms and muscle (co-)contractions that induce abnormal movements and/or postures. In general it is a relatively unknown entity and it is estimated that as few as 5% is correctly diagnosed (Dystonia Medical Research Foundation). Classification of dystonia is according to its etiology, distribution and phenomenology. Focal dystonias occur in the facial or neck muscles, e.g. blepharospasm and spasmodic torticollis, or in the upper extremity, e.g. occupational cramps ("craft palsy"), like writer's or musician's cramp.

Musician's cramp is of unknown organic cause (primary), it is a localised (focal), unintended, simultaneous activity of agonists and antagonists, inducing abnormal movements and/or postures (dystonia), mainly of the hands and fingers, but sometimes of facial (embouchure ! ) or neck-muscles (torticollis). It is usually painfree. It is a task specific "disorder of excellence", which means that it only occurs with one demanding, highly specialised, professional skilled motor act, like writing or playing a musical instrument. So musician's cramp is a primary, focal, task specific dystonia.

EMG (=electromyography) may support the diagnosis and show inappropriate tonic co-contraction of antagonistic muscles or musclegroups.

Epidemiology of focal dystonia in musicians:

In our patient population of consecutive injured musicians the prevalence of focal dystonia is 4,5% (1998: 38/871). They played the following instruments:

guitar

12

saxophone

3+1*

trumpet

1*

harp

1

piano/organ

7

flute

3

double-bass

1

percussion

1

violin

3+1**

accordion

2

cello

1

French horn

1**


* = embouchure
** = taskspecific torticollis.

In comparison with the representation of 7% guitarists in the overall group of our musician-patients, the high proportion of 32% ( 12/38 ) guitarists in our focal dystonia series is striking and as yet unexplained. It comes as no surprise that in the guitar literature this condition is also known as guitarist's cramp.

Several of our focal hand-dystonia musician-patients had a co-existing ulnaropathy. This is also mentioned in the literature. (Charness et al.) At this point some explanation of ulnaropathy in musicians is appropriate.

Possible relation of focal dystonia in musicians and ulnaropathy at the elbow (= cubital tunnel syndrome):

In our total musician-patients population neuropathy of the ulnar nerve in the elbow region (ulnaropathy or cubital tunnel syndrome) is relatively common. We found a 9 % overall prevalence of ulnaropathy.

This high prevalence may be explained because the ulnar nerve is at risk in the cubital tunnel during the playing of a musical instrument, due to the following factors: Flexion of the elbow gives stretch and tension on the ulnar nerve in the cubital tunnel, which is at the same time compressed by the aponeurosis formed by the two heads of the m.flexor carpi ulnaris. This muscle is active in stabilizing the os pisiforme in the carpus during abduction of the fifth finger, which in musicians is frequent, controlled and forceful. Also in musicians, due to all its activity in innervating the intrinsic handmusculature, there will be slight swelling and edema around the ulnar nerve due to increased blood-circulation, which may further impair its free course and make it more vulnerable. In some instruments (e.g. right arm in harp and guitar) local pressure may be a contributing factor.

The diagnosis of ulnaropathy in musicians is based on the history of pain on the medial side of the elbow, often aggravating while playing their musical instrument. Paresthesias to the 4th and 5th fingers are common, but are rarely mentioned spontaneously. In case of night- or morning-pain and/or -paresthesias sleeping position should be questioned. A positive Tinel's sign over the cubital tunnel seems to be the most reliable finding on physical examination. There may be anterior (sub-)luxation of the nerve, usually at 90 degrees of flexion of the elbow and sometimes with a painful click. This is clearly demonstrable with ultrasound imaging.

Since the ulnar nerve is the motor nerve for the intrinsic hand musculature, which is vital to fine coördination, a musician will feel any loss of control long before there actually is loss of sensation or weakening. So, EMG-registration will rarely register any disturbances. Sometimes impairment of the UNCV (ulnar nerve conduction velocity) can be demonstrated with the special "inching" technique, measuring the UNCV per inch, in different portions of the ulnar nerve. Conservative treatment consists of extensive explanation, general relaxation, night splints, posture and instrument-technique correction.

If conservative treatment fails operative release and anterior transposition of the ulnar nerve gives invariably good results without nerve damage, provided the precious motor-branch to the m.flexor carpi ulnaris is saved and rehabilitation is closely and expertly supervised. Anterior transposition of a symptomatic ulnar nerve in our musician-patients with focal dystonia gave good improvement of the ulnaropathy and some improvement of the dystonic complaints, but unfortunately did not result in complete recovery of the latter. Although there may be some relation, as yet it is uncertain whether the ulnaropathy is cause of - or caused by the focal dystonia. It may just be a coïncidence, given the high prevalence of ulnaropathy in 9% of the musician-patients.

Etiology of focal dystonia in musicians:

In 1995 Leijnse postulated that there may be a relation between focal hand-dystonia in musicians and tendinous connections ("anatomical constraints") in the hand. Hypothetically complete recovery might be expected after cutting these connections. Leijnse devised a machine to test for these connections and he has analysed several of our musician-patients: free motion limiting tendinous connections were indeed demonstrated in some cases and operated by Sonneveld, handsurgeon in Rotterdam, with promising results, but complete recovery is not yet reported and prolonged rehabilitation is necessary.

This raises the question if hand-dystonias in musicians are one homogenous group, if they are in fact primary dystonias and if they are rightfully classified in the same group of primary focal dystonias as e.g. the cranial dystonias and the spasmodic torticollis.

Allthough there still is more mystery and controversy than consensus about its etiology, the fact that some of our musician-patients with hand-dystonia show the phenomenon of contralateral activation and mirror movements (or synergy) actually proves that it is a central movement control disorder. This fact has not yet been reported in the literature on focal dystonia in musicians and will be shown on video.

Our etiology hypothesis is that focal hand-dystonia in musicians is a central motor-control disorder (Rietveld and Moll, 1998, unpublished data), which may be triggered peripherally by a failing coping mechanism compensating for tendinous connections in the hand (Leijnse, 1995, thesis). This hypothesis is supported by the fact that neuro-imaging studies showed that musicians with focal hand dystonia exhibit overlap or "smearing" of the representational zones of the digits of the dystonic hands in the somatosensory cortex of the brain (Elbert et al.).

Treatment of focal dystonia in musicians:

As yet there is no effective standard treatment for focal dystonia in musicians. Except for the radical cutting of causative tendinous connections in the hands, treatment is largely symptomatic, because, in spite of the etiology-hypotheses, its cause is as yet uncertain. Symptomatic treatments that are tried more or less successfully are:

  • Movement therapy: It was shown in a pilot study (Candia et al.) that independent hand and finger-function in focal dystonia in musicians may recover with constraint-induced movement therapy. Successful movement therapy is also claimed by Ph.Chamagne, a fysiotherapist in Paris, France.

  • Anticholinergic drugs: Trihexifenidyl (Artane), a centrally direct acting parasympaticolytic drug used in Parkinsons' disease, may give improvement in some cases.

  • Botulinum toxin type A (Dysport , Botox): This is injected in a dystonic muscle and gives a temporary and local paralysis of the injected muscle. After some weeks up to three months the (ab-)normal motorfunction returns and injection may have to be repeated with a lesser or higher dose. Despite of successful administration of botulinum toxin in writer's cramp (Koelman et al.) botulinum toxin-injections for musician's cramp in our hands has been dissappointing: only in two of our cases, in a professional flute-player and in a pianist, there is a satisfactory improvement on repeated (each three months...) injections.

Conclusion:

Although musicians suffering of focal dystonia (musicians' cramp) find great relief in the fact that somebody recognises their disease and acknowledges it as a somatic ailment, much remains to be done to clarify its causes, evaluate the proper classification and find effective treatment options for this devastating, career threatening and usually career ending, disorder.

Literature:

  • Bradley WG et al. Neurology in clinical practice. Vol.2. Butterworth. Dystonia. 1996:1751-56

  • Brandfonbrener AG. Musicians with focal dystonia. Med.Probl.Perform.Art.1991;6:132-6

  • Candia V, Elbert T, Altenmüller E, Rau H, Schäfer T, Taub E. Lancet 1999;353:42

  • Charness ME, Ross JH, Shefner JM. Ulnar neuropathy and dystonic flexion of the fourth and fifth digits. Muscle Nerve 1996;19:431-7

  • Elbert T, Candia V, Altenmüller E, et al. Alteration of digital representation in somatosensory cortex in focal hand dystonia. Neuroreport 1998; 9

  • Koelman JHTM, Struys MA, Ongerboer de Visser BW, Speelman JD. Schrijfkramp behandeld met botuline injecties. Ned.Tijdschr.Geneeskd 1998;142:1768-71

  • Lederman RJ. Focal dystonia in instrumentalists. Med.Probl.Perform.Art.1991;6:132-6

  • Leijnse JNAL. Finger exercises with anatomical constraints. 1995 Thesis

  • Rietveld ABM, Moll LCM. 1998 Unpublished data

© Boni Rietveld, Heemstede, 7 maart 1999
Ref.: BR/wp/abstract/Sanitas.doc


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