Writer's Cramp

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 commonest 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.¹

It is difficult to know the true incidence of the condition as most sufferers do not seek medical attention. The picture is rather complex.³ 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 hand writing is increasingly replaced by use of a keyboard.

Risk factors²

These would seem to be doing a great deal of hand writing 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.⁴ Symptoms follow an accident to the hand or arm in 5 to 10%.

History

• 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.

Examination

• 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.⁶ 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.⁷ 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).⁸
• Electromyelography (EMG) may show simultaneous contraction of agonists and antagonists.⁹
• Nerve conduction studies may be required to exclude a trapped nerve.⁷
• An MRI scan may be indicated if a structural lesion is suspected.²

• 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.
• Hand writing training produces improvement but does not bring return to normality.¹⁰ Using a modified pen grip is sometimes beneficial.¹⁰
• 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.²
• Transcutaneous electrical nerve stimulation (TENS) gives better results than placebo.¹¹
• A number of drugs, especially anticholinergics and L dopa, have been used with little benefit but botulinum toxin injection seems the most effective.⁹ Patients who are most likely to benefit can be identified.¹²
• In exceptional cases stereotactic nucleus ventrooralis thalamotomy may be of value.¹³

Prognosis is variable, as is response to treatment. Many patients stabilise within five years but the condition can recur, particularly at times of stress.¹⁴