Writer's Cramp

Author: Jonathan B Strober, MD; Chief Editor: Selim R Benbadis, MD more...

Updated: May 10, 2012

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Background
Pathophysiology
Epidemiology
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Background

Writer's cramp is a form of task-specific focal dystonia. Dystonia is an involuntary, sustained muscle contraction causing twisting movements and abnormal postures; focal dystonia means only one body part is affected. Writer's cramp is the most common dystonia occurring in the setting of repetitive movement disorders. A focal dystonia can sometimes be the first manifestation of a generalized dystonia.

Pathophysiology

Normally, an antagonist muscle relaxes when an agonist muscle is contracted. Patients with dystonia have simultaneous contraction of both groups of muscles. Spinal reciprocal inhibition, a process that inhibits the antagonist muscles when the agonist muscles are active, is reduced in patients with writer's cramp. This is most probably due to aberrant descending commands.

Abnormalities in the basal ganglia lead to abnormalities of sensory processing and motor output. The normal increase in cerebral blood flow in the supplementary motor area is reduced in response to vibration and abnormal somatosensory evoked potentials. These provide evidence for the abnormal sensory processing in patients with dystonia. Increased motor cortex excitability along with decreased cortical inhibition causes abnormal motor output.

Frequency

United States

One study estimated the prevalence to be 69 cases per 100,000 population; this is thought to be an underestimation because a high percentage of patients never seek medical assistance.

International

Again, because of the small percentage of affected patients seeking medical attention, accurate prevalence estimates are not available.

Sex

Prevalence is slightly higher in men; the male-to-female ratio is 1.3:1.

Age

Typically, patients present in the third to fifth decades, and women usually present earlier than men.

Proceed to Clinical Presentation

Contributor Information and Disclosures

Author

Jonathan B Strober, MD Director, Pediatric Muscular Dystrophy Association Clinic; Associate Clinical Professor, Departments of Pediatrics and Neurology, Division of Child Neurology, University of California at San Francisco

Jonathan B Strober, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, Child Neurology Society, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Stephen T Gancher, MD Adjunct Associate Professor, Department of Neurology, Oregon Health Sciences University

Stephen T Gancher, MD is a member of the following medical societies: American Academy of Neurology, American Neurological Association, and Movement Disorders Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Nestor Galvez-Jimenez, MD, MSc, MHA Chairman, Department of Neurology, Program Director, Movement Disorders, Department of Neurology, Division of Medicine, Cleveland Clinic Florida

Nestor Galvez-Jimenez, MD, MSc, MHA is a member of the following medical societies: American Academy of Neurology, American College of Physicians, and Movement Disorders Society

Disclosure: Nothing to disclose.

Chief Editor

Selim R Benbadis, MD Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida College of Medicine

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association

Disclosure: UCB Pharma Honoraria Speaking, consulting; Lundbeck Honoraria Speaking, consulting; Cyberonics Honoraria Speaking, consulting; Glaxo Smith Kline Honoraria Speaking, consulting; Pfizer Honoraria Speaking, consulting; Sleepmed/DigiTrace Honoraria Speaking, consulting

References

Tinazzi M, Farina S, Bhatia K, Fiaschi A, Moretto G, Bertolasi L, et al. TENS for the treatment of writer's cramp dystonia: a randomized, placebo-controlled study. Neurology. Jun 14 2005;64(11):1946-8. [Medline].
Goto S, Shimazu H, Matsuzaki K, Tamura T, Murase N, Nagahiro S, et al. Thalamic Vo-complex vs pallidal deep brain stimulation for focal hand dystonia. Neurology. Apr 15 2008;70(16 Pt 2):1500-1. [Medline].
Baur B, Schenk T, Furholzer W, Scheuerecker J, Marquardt C, Kerkhoff G, et al. Modified pen grip in the treatment of Writer's Cramp. Hum Mov Sci. Oct 2006;25(4-5):464-73. [Medline].
Chen R, Hallett M. Focal dystonia and repetitive motion disorders. Clin Orthop. Jun 1998;(351):102-6. [Medline].
Chen RS, Tsai CH, Lu CS. Reciprocal inhibition in writer's cramp. Mov Disord. Sep 1995;10(5):556-61. [Medline].
Cohen LG, Hallett M. Hand cramps: clinical features and electromyographic patterns in a focal dystonia. Neurology. Jul 1988;38(7):1005-12. [Medline].
Epidemiologic Study of Dystonia in Europe (ESDE) Collaborative Group. Sex-related influences on the frequency and age of onset of primary dystonia. Neurology. Nov 10 1999;53(8):1871-3. [Medline].
[Best Evidence] Kruisdijk JJ, Koelman JH, Ongerboer de Visser BW, de Haan RJ, Speelman JD. Botulinum toxin for writer's cramp: a randomised, placebo-controlled trial and 1-year follow-up. J Neurol Neurosurg Psychiatry. Mar 2007;78(3):264-70. [Medline].
Marsden CD, Sheehy MP. Writer's cramp. Trends Neurosci. Apr 1990;13(4):148-53. [Medline].
Rhoad RC, Stern PJ. Writer's cramp--a focal dystonia: etiology, diagnosis, and treatment. J Hand Surg Am. May 1993;18(3):541-4. [Medline].
Schmidt A, Jabusch HC, Altenmuller E, et al. Dominantly transmitted focal dystonia in families of patients with musician's cramp. Neurology. Aug 22 2006;67(4):691-3. [Medline].

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