WRITER’S CRAMP

Synonyms – Mogigraphia , Scrivener’s palsy

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.


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


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.

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.

Clinical

History –
Incoordination, cramping, and aching of the hand with task-specific movements are usually the
initial complaints.
The hand assumes a semiflexed position of the fingers with possible hyperextension of the fingers
and hyperflexion or extension of the wrist with supination or pronation.
The symptoms become exaggerated with attempts to perform a specific task, such as writing. In somecases, the hand may dart across the page with a sudden jerk.
A related condition is primary writing tremor. Affected individuals exhibit a prominent large amplitude tremor only with writing.

Physical
Neurologic examination findings are usually normal.
Subtle findings include mild dystonic postures developing either spontaneously or with movement and reduced arm swing.
One third of patients have a tremor in the affected arm or hand while writing or when the extremity is outstretched. Observation of the limb during writing is an important part of the examination; the
assumption of dystonic postures should be demonstrable. Patients affected with primary writing tremor, a variant of writer's cramp, may exhibit a large-amplitude tremor only during writing. In
contrast to essential tremor, action or sustentation tremors are not seen with other tasks such as holding a full cup of liquid or coordination testing. Dystonic posturing is usually not seen with this condition.

Causes
Writer's cramp frequently affects persons who write a great deal or perform other repetitive hand movements such as typing.
Approximately 5% of patients have a positive family history of a similar condition.
Five to ten percent report an accident or injury to the hand or arm immediately preceding the onset of symptoms.
Several possible, but rare, associations have been reported, including C6 ruptured disk, lithium use, basalganglia or cortical tumors, arteriovenous malformations (AVMs), and stroke. However, most cases are idiopathic.

Differential Diagnoses

Dopamine-Responsive Dystonia
Multiple Sclerosis
Parkinson Disease
Wilson Disease
Primary writing tremor
Postural tremor
Idiopathic torsion dystonia

Workup

Imaging Studies - MRI - If a structural lesion is suspected
Procedures - Electromyography/nerve conduction studies
To evaluate for nerve injury, if trauma is the suspected cause
Confirm diagnosis by showing simultaneous contraction of agonist and antagonist muscles

Treatment

Medical Care

Approximately 5% of patients have spontaneous remission, most probably in the first 5 years.
However, the majority of these patients have relapses.Treatment is generally disappointing.
Transcutaneous electrical nerve stimulation (TENS) delivered to the forearm flexor muscles for
a 2-week period has been found to improve symptoms for upto 3 weeks after treatment.
Behavioral changes may help.
Biofeedback, hypnotherapy, and relaxation therapy have been tried.


Activity

Altering the grip of the pen and/or increasing the diameter of the pen used is the first step in treatment. Patients can use a writing device or other means of transcription, such as typing or dictation.

Medication

Several classes of drugs have been used in patients with writer's cramp. Anticholinergics have had conflicting results. Beta-blockers have helped the tremor in a few patients. Botulinum toxin injections seem to have the best results.

Anticholinergic

Blocking cholinergic innervation of the basal ganglia is hypothesized to increase the dopaminergic effect,thereby reducing dystonia.
Trihexyphenidyl (Artane)
Substituted piperidine that inhibits parasympathetic system. Available as 2 mg tab or 2 mg/5 cc
elixir.

Adult

Start with 1 mg PO qd, then increase by 2 mg at intervals of 3-5 d up to 6-15 mg/d divided tid
Dosing Interactions Contraindications Precautions
Dosing Interactions Contraindications Precautions
Beta-adrenergic blockers
These agents help reduce the tremor.
Propranolol (Inderal, Betachron E-R)
Class II antiarrhythmic, nonselective, beta-adrenergic, receptor blocker with membrane-stabilizing activity that decreases automaticity of contractions. Available as 10 mg, 20 mg, 40 mg, and 80 mg tablets and 60 mg, 80 mg, 120 mg, and 160 mg long-acting tablets (Inderal LA)


Neurotoxins
Neurotoxin complex blocks neuromuscular conduction by binding to receptor sites on motor nerve  terminals, entering the nerve terminals, and inhibiting the release of acetylcholine. When injected intramuscularly, it produces a localized chemical denervation muscle paralysis.

Botulinum toxin type A (BOTOX®)
Local intramuscular injections weaken overactive muscles, reducing dystonic symptoms.
Pediatric - Administer as in adults

Adult - 40 mg PO bid initially; increase as tolerated; not to exceed 240-320 mg/d divided bid/tid

Pediatric - 2-4 mg/kg PO divided bid; increase as tolerated; not to exceed 16 mg/kg/d

Adult - Injections usually given under EMG guidance and should be administered by physicians experienced in giving the injections
Pediatric - Not established

Follow-up

Prognosis - The prognosis is good.
Patient Education - Patients should reduce the task-specific activities that precipitate the
condition.

Medicolegal Pitfalls - Do not consider patients with writer's cramp and other action dystonias as having a psychiatric disorder.This could deprive the patient of evaluation by a movement
disorder specialist and hence the benefit of adequate treatment. Patients with writer's cramp do not have a higher incidence of psychiatric disorder than the general population.