Focal dystonia

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. this occurs most commonly in the hand, and is known as Focal Hand Dystonia.

The affected population includes individuals who require repetitive movements in their regular daily life, with one of the most affected populations being musicians and professional writers.[1] In the European and American populations, Focal Dystonia varies its prevalence between 3 and 29.5 per 100.000 inhabitants.[1][2] With dystonia occurring in musicians, it is estimated that 0.5 -1% of all musicans suffer some form of focal dystonia.[1][3] These figures are highly variable if we individualize each case, depending on the instrument and the effort required with each performance; for example, the difference between a rhythm and a soloist guitar player.

[4]

Mechanism of Injury / Pathological Process

Although the pathological process of Focal Dystonia is still classified as idiopathic, increasing evidence suggested a multifactorial etiology[5] (i.e. interaction between genetic, neuromuscular, auditory, neural adaptative, anatomic, stressful, repetitive, psychosocial, traumatic, among others). An alteration in tactile discrimation was found in dystonic musicians compared to generalized dystonias and healthy controls; this has been related with the superposition of the areas of cortical representation of the fingers affected in musicians.[1][6] Other etiological mechanisms are also described in the literature, such as the alteration of inhibitory spinal, trunk, and intracortical as well as alterations in sensorimotor integration.[1]

Many triggering factors have been described in current literature and can be separated into external and internal factors. Extrinsic factors include spatial, temporal, and spatial constraints, depending on the workload of the respective body part and the complexity of the movements used. Intrinsic factors include the need of control, the need of perfectionism, anxiety, local pain, trauma, overuse and the deficit in inhibitory mechanisms. Predisposing factors such as genetics and sex are also important. These triggering factors combined can affect the manifestation of Dystonia.[7]

Clinical Presentation

Some examples of Focal Dystonia are Cervical Dystonia (AKA spasmodic torticollis), which causes the neck to twist or tilt, Musician's Dystonia, Writer's Dystonia, Blepharospasm (bilateral, involuntary, synchronous, forceful eye closure) and Spasmodic Dystonia, among others. Musician's and Writer's Dystonia are referenced in this article.

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.[7] This loss of muscle coordination is often accompannied by a co-contraction of antagonist muscles.[7]

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. Tremor and spasms of the hand can also occur.

Diagnostic Procedures

Magnetic Resonance Imaging (MRI) - to exclude stroke or tumours involving the basal ganglia

Bloodwork to assess ceruloplasmin levels - to rule out Wilson's disease (a disorder of copper metabolism that can produce dystonia and other movement disorders)

Outcome Measures

Motor control and ADL scales

Management / Interventions

  • Botulin Toxin[8]
  • Surgery 
  • Ergonomic changes at the instrument (Musician's dystonia)
  • Immobilization[9]
  • Behavioral training[10][5]
  • Drug management includes: Anticholinergics[11], Baclofen and benzodiazepines

Physiotherapy

  • TENS[12]
  • Sensomotor Training[6]
  • Muscle Strengthening
  • Stretching
  • Relaxation Techniques
  • Home exercises[5]
[13]

Differential Diagnosis

  • Paroxysmal dystonia: this presents as discrete episodes of abnormal movements lasting from minutes to hours, with intervening periods of normalcy[14]
  • Dopa-responsive dystonia: this is characterized by diurnal variation of dystonic movements, with improvement in the morning and worsening in the afternoon[15]; it is linked to chromosome 14, which is involved in dopamine synthesis
  • Dystonic tics (which may be associated with obsessive-compulsive disorder): patients with dystonic tics feel an internal, uncomfortable sensation in the affected body part, and this sensation builds up to an overwhelming "urge" to perform a sustained, tonic tic e.g. head turning; patients often report relief immediately after performing the tic, but this is soon followed by recurrence of the urge to perform the tic again
  • Iatrogenic causes: dopamine receptor-blocking medications, e.g. neuroleptics and phenothiazine-based antiemetics, can produce an acute dystonic reaction from a single dosage, or tardive dystonia from chronic usage[16]


References

  1. 1.0 1.1 1.2 1.3 1.4 Aranguiz, R., Chana-Cuevas, P., Alburquerque, D. Leon, M. (2011). Focal dystonia in musicians. Neurologia, 26(1), 45-52. doi: 10.1016/j.nrl.2010.09.019
  2. Defazio, G., Abbruzzese, G., Livrea, P. Berardelli, A. (2004). Epidemiology of primary dystonia. Lancet Neurol, 3(11), 673-678. doi: 10.1016/s1474-4422(04)00907-x
  3. Jabusch, H. C., Zschucke, D., Schmidt, A., Schuele, S., Altenmuller, E. (2005). Focal dystonia in musicians: treatment strategies and long-term outcome in 144 patients. Mov Disord, 20(12), 1623-1626. doi: 10.1002/mds.20631
  4. Associated Press. Musician Billy McLaughlin Outwits Focal Dystonia. Available from: http://www.youtube.com/watch?v=cNOkvG-15wA [last accessed 29/08/16]
  5. 5.0 5.1 5.2 Byl, N. N., Archer, E. S.; McKenzie, A. (2009). Focal hand dystonia: effectiveness of a home program of fitness and learning-based sensorimotor and memory training. J Hand Ther, 22(2), 183-197; quiz 198. doi: 10.1016/j.jht.2008.12.003
  6. 6.0 6.1 Byl, N. N., Nagajaran, S.McKenzie, A. L. (2003). Effect of sensory discrimination training on structure and function in patients with focal hand dystonia: a case series. Arch Phys Med Rehabil, 84(10), 1505-1514.
  7. 7.0 7.1 7.2 Altenmuller, E. Jabusch, H. C. (2010). Focal dystonia in musicians: phenomenology, pathophysiology, triggering factors, and treatment. Med Probl Perform Art, 25(1), 3-9.
  8. Ceballos-Baumann, A. O., Sheean, G., Passingham, R. E., Marsden, C. D. Brooks, D. J. (1997). Botulinum toxin does not reverse the cortical dysfunction associated with writer's cramp. A PET study. Brain, 120 ( Pt 4), 571-582.
  9. Priori, A., Pesenti, A., Cappellari, A., Scarlato, G. Barbieri, S. (2001). Limb immobilization for the treatment of focal occupational dystonia. Neurology, 57(3), 405-409 (abstract only)
  10. Berque, P., Gray, H., Harkness, C. McFadyen, A. (2010). A combination of constraint-induced therapy and motor control retraining in the treatment of focal hand dystonia in musicians. Med Probl Perform Art, 25(4), 149-161 (abstract only).
  11. Fahn S, Burke R, Stern Y: Antimuscarinic drugs in the treatment of movement disorders. Progr Brain Res 1990; 84:389-397
  12. Tinazzi, M., Zarattini, S., Valeriani, M., Stanzani, C., Moretto, G., Smania, N., . . . Abbruzzese, G. (2006). Effects of transcutaneous electrical nerve stimulation on motor cortex excitability in writer's cramp: neurophysiological and clinical correlations. Mov Disord, 21(11), 1908-1913. doi: 10.1002/mds.21081
  13. Dr. Larry Santora. Physical therapy for focal hand dystonia. Available from: http://www.youtube.com/watch?v=Ihew0-BAkC8 [last accessed 29/08/16]
  14. Demirkiran M, Jankovic J: Paroxysmal dyskinesias: clinical features and classification. Ann Neurol 1995; 38:571-579
  15. Ichinose H, Ohye T, Takahashi E, et al: Hereditary progressive dystonia with marked diurnal fluctuation caused by mutations in the GTP cyclohydrolase I gene. Nat Genet 1994; 8:236-242
  16. Miller LG, Jankovic J: Neurologic approach to drug-induced movement disorders: a study of 125 patients. South Med J 1990; 83:525-532