Writer's cramp is a type of focal dystonia that is specific to the task. Dystonia is an involuntary, sustained muscle contraction. Focal dystonia affects only one body part. Writer's cramp is the most common dystonia of the repetitive movement disorders. Cerebellar abnormalities have been detected but it is not known whether these are the cause or the effect of writer's cramp. An MRI study of activity in the Brodmann area of the cortex suggested decreased baseline activity, or an impaired activation in response to motor tasks in patients with writer's cramp, for the dystonic and the clinically unaffected hand.
It is difficult to know the true incidence of the condition as most sufferers do not seek medical attention. The picture is rather complex. It is thought to be most prevalent between the ages of 30 and 50. There is a slight male preponderance but females tend to present slightly earlier. It is likely that the condition is becoming less frequent as writing with the hand is increasingly replaced by use of a keyboard.
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These would seem to be doing a great deal of writing by hand without adequate breaks, and possibly gripping the pen too tightly. 5-20% give a family history of this or a similar condition and it is highly likely that there is a genetic component in these cases. Indeed, a genetic defect has been found in some patients. Symptoms follow an accident to the hand or arm in 5-10%.
One study also identified that:
- Cases had a college or university degree more frequently than controls.
- The risk of writer's cramp increased with the time spent writing each day.
- It was also associated with an abrupt increase in the writing time during the year before onset.
- Head trauma with loss of consciousness and myopia were both associated.
The study found no association with peripheral trauma, left-handedness, constrained writing, writing in stressful situations or the choice of writing tool.
- Prolonged periods of writing cause cramping, aching and incoordination of the hand. As the condition progresses, the duration required to produce these symptoms reduces.
- There is often an exaggeration of the normal semiflexed position of the fingers, but hyperextension of the distal interphalangeal joint of the index finger. There may also be hyperflexion or extension of the wrist with supination or pronation.
- Symptoms may become exaggerated with attempts to write and the hand may even dart across the page with a sudden jerk.
- One third of patients have a tremor in the affected arm or hand while writing or when the arm is outstretched.
- There may be very subtle findings like mild dystonic postures developing, either spontaneously or with movement, and reduced arm swing on walking.
- Neurological examination reveals no abnormality.
- Observe the patient writing. Dystonic postures should be apparent.
- Parkinson's disease causes difficulty with writing but with micrographia and distinct physical signs.
- If other dystonias are found, there should be suspicion of a more general dystonia syndrome.
- Neurological signs suggest a different diagnosis, such as multiple sclerosis or Wilson's disease.
- Compartment syndrome of the forearm causes cramp and may need to be excluded if discomfort is a predominant feature.
- Primary writing tremor is a variant of writer's cramp with large-amplitude tremor only during writing. Dystonic posturing is unusual with this condition.
- Repetitive strain injury (RSI) related to keyboard use is probably replacing writer's cramp to a large extent. Musicians can also get repetitive cramp if they have practised for many hours a day.
- The diagnosis is essentially clinical . Functional assessments such as the Arm Dystonia Disability Scale (ADDS) or Writer's Cramp Rating Scale (WCRS) may be useful in some patients, as may kinematic analysis of handwriting movements (kinematics = the study of motion).
- Electromyelography (EMG) may show simultaneous contraction of agonists and antagonists.
- Nerve conduction studies may be required to exclude a trapped nerve.
- An MRI scan may be indicated if a structural lesion is suspected.
- Reducing the amount of writing that is done is basic to an overuse syndrome. Use of a keyboard instead of a pen may help.
- There may be some benefit from using a wider pen or an attachment to make it wider.
- Training to write with the hand and using a modified pen grip are sometimes beneficial.
- Treatment aimed at facilitating interdigit separation of digits 1, 2 and 3 may be beneficial.
- Psychological treatment, such as habit reversal, seems no better than relaxation exercises. Historically there has been a tendency to classify the condition as a neurosis but the evidence points to a physical aetiology.
- Behavioural techniques, such as auditory grip force feedback (using an auditory signal to indicate grip strength), has been found beneficial.
- Transcutaneous electrical nerve stimulation (TENS) gives better results than placebo.
- A number of drugs, especially anticholinergics and L-dopa, have been used with little benefit but botulinum toxin injection seems the most effective. Patients who are most likely to benefit can be identified.
- Thalamic deep brain stimulation has been helpful in some patients.
- In exceptional cases, stereotactic nucleus ventrooralis thalamotomy may be of value.
Prognosis is variable, as is response to treatment. Many patients stabilise within five years but the condition can recur, particularly at times of stress.
Further reading & references
- Delmaire C, Vidailhet M, Elbaz A, et al; Structural abnormalities in the cerebellum and sensorimotor circuit in writer's cramp. Neurology. 2007 Jul 24;69(4):376-80.
- Strober J; Writer's Cramp eMedicine.com 2006
- Defazio G, Abbruzzese G, Livrea P, et al; Epidemiology of primary dystonia. Lancet Neurol. 2004 Nov;3(11):673-8.
- Bhidayasiri R, Jen JC, Baloh RW; Three brothers with a very-late-onset writer's cramp. Mov Disord. 2005 Oct;20(10):1375-7.
- Ritz K, Groen JL, Kruisdijk JJ, et al; Screening for dystonia genes DYT1, 11 and 16 in patients with writer's cramp. Mov Disord. 2009 Jul 15;24(9):1390-2.
- Koukouni V, Valente EM, Cordivari C, et al; Unusual familial presentation of epsilon-sarcoglycan gene mutation with falls and Mov Disord. 2008 Oct 15;23(13):1913-5.
- Roze E, Soumare A, Pironneau I, et al; Case-control study of writer's cramp. Brain. 2009 Mar;132(Pt 3):756-64. Epub 2009 Jan 29.
- Moberg-Wolff E et al, Dystonias, Medscape, Jan 2010
- Modugno N, Nakamura Y, Bestmann S, et al; Neurophysiological investigations in patients with primary writing tremor. Mov Disord. 2002 Nov;17(6):1336-40.
- Keller K, Corbett J, Nichols D; Repetitive strain injury in computer keyboard users: pathomechanics and treatment principles in individual and group intervention. J Hand Ther. 1998 Jan-Mar;11(1):9-26.
- Zeuner KE, Peller M, Knutzen A, et al; How to assess motor impairment in writer's cramp. Mov Disord. 2007 Jun 15;22(8):1102-9.
- Gordon NS; Focal dystonia, with special reference to writer's cramp. Int J Clin Pract. 2005 Sep;59(9):1088-90.
- Baur B, Furholzer W, Jasper I, et al; Effects of modified pen grip and handwriting training on writer's cramp. Arch Phys Med Rehabil. 2009 May;90(5):867-75.
- Nelson AJ, Blake DT, Chen R; Digit-specific aberrations in the primary somatosensory cortex in Writer's cramp. Ann Neurol. 2009 Aug;66(2):146-54.
- Baur B, Furholzer W, Marquardt C, et al; Auditory grip force feedback in the treatment of Writer's cramp. J Hand Ther. 2009 Apr-Jun;22(2):163-70; quiz 171. Epub 2009 Feb 1.
- Tinazzi M, Zarattini S, Valeriani M, et al; Effects of transcutaneous electrical nerve stimulation on motor cortex excitability in writer's cramp: neurophysiological and clinical correlations. Mov Disord. 2006 Nov;21(11):1908-13.
- Djebbari R, du Montcel ST, Sangla S, et al; Factors predicting improvement in motor disability in writer's cramp treated with botulinum toxin. J Neurol Neurosurg Psychiatry. 2004 Dec;75(12):1688-91.
- Cho CB, Park HK, Lee KJ, et al; Thalamic Deep Brain Stimulation for Writer's Cramp. J Korean Neurosurg Soc. 2009 Jul;46(1):52-5. Epub 2009 Jul 31.
- Taira T, Harashima S, Hori T; Neurosurgical treatment for writer's cramp. Acta Neurochir Suppl. 2003;87:129-31.
- Prognosis; Dystonia Medical Research Foundation 2007
|Original Author: Dr Laurence Knott||Current Version: Dr Laurence Knott|
|Last Checked: 22/01/2010||Document ID: 2944 Version: 21||© EMIS|
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