Botulinum toxin for writer's cramp: a randomised, placebo-controlled trial and 1-year follow-up

Background

Botulinum toxin type A (BoNT‐A) has become the treatment of choice for most types of focal dystonia.

Objective

To investigate the efficacy of BoNT‐A injections in patients with writer''s cramp in a double‐blind, randomised, placebo‐controlled trial and to evaluate the follow‐up results.

Methods

Forty participants were randomised to treatment with either BoNT‐A or placebo injections in two sessions. Trial duration was 12?weeks. The primary outcome measure was the patients'' choice to continue with the treatment, despite its possible disadvantages. Secondary outcome measures included several clinical rating scales on the levels of impairment and disability. Assessments were made at baseline and 2?months (secondary outcomes) and 3?months (primary outcome). Duration of follow‐up was 1?year.

Results

39 patients completed the trial. Fourteen of 20 patients (70%) receiving BoNT‐A reported a beneficial effect and chose to continue treatment, versus 6 of 19 patients (31.6%) in the placebo group (p?=?0.03). The changes on most of the clinical rating scales were significantly in favour of BoNT‐A. Side effects reported were hand weakness, which was mostly mild and always transient, and pain at the injection site. After 1?year, 20 of 39 patients were still under treatment with a positive effect.

Conclusion

Treatment with BoNT‐A injections led to a significantly greater improvement compared with placebo, according to patients'' opinion and clinical assessment scales. Weakness in the hand is an important side effect of BoNT‐A injections, but despite this disadvantage, most patients preferred to continue treatment. About 50% of our patients were still under treatment after 1?year.Writer''s cramp is a task‐specific, focal hand dystonia. It is characterised by involuntary, repetitive or sustained contractions of finger, hand or arm muscles that occur during writing and produce abnormal postures or movements that interfere with normal handwriting.^1,2,3,4 Two categories are recognised: simple writer''s cramp, in which dystonic posturing of the hand and arm occurs only during writing, and complex or dystonic writer''s cramp, in which the condition manifests also during other manual tasks and sometimes with spontaneous abnormal posturing.^1,2,5 In most patients, no specific cause can be identified. Although the prevalence is relatively low, varying from 3 to 7/100?000,^6,7,8 writer''s cramp may be responsible for considerable morbidity in terms of working impairment, pain, embarrassment, low self‐esteem and poor social interaction.Therapeutic recommendations have included physical treatment, postural and writing re‐education exercises, relaxation techniques, hypnosis, biofeedback, use of special writing devices, acupuncture and transcranial magnetic stimulation, but most of the patients do not obtain satisfactory and sustained benefit.^9,10,11,12 Some patients learn to write with their non‐dominant hand, but there is a 25% chance that this hand will become afflicted with the same problem.¹³ Drug treatment has been disappointing so far.^3,9,14 The use of splints or braces and constraint‐induced movement treatment may occasionally be helpful, but it is not clear if they produce sustained relief.^15,16,17 There is presently only limited experience with stereotactic neurosurgical procedures for focal hand dystonia.^18,19 The treatment of dystonic syndromes such as blepharospasm and cervical dystonia has been much improved by the introduction of botulinum toxin as a therapeutic agent.^20,21 When botulinum toxin is injected into muscles, the toxin produces local chemodenervation by interfering with the release of acetylcholine from the presynaptic nerve terminal.⁴ However, there are also several drawbacks. Firstly, the effects of botulinum toxin type A (BoNT‐A) are not permanent, lasting for only approximately 3?months; thus, regular injections are required. Secondly, inconvenient muscle weakness interfering with other non‐writing activities may occur.²² Regarding the treatment of writer''s cramp, three randomised, double‐blind, placebo‐controlled studies have been undertaken, however, with small numbers of patients, different methods and inconclusive results.^23,24,25We performed a randomised, double blind, placebo‐controlled trial in 40 patients with writer''s cramp, to assess whether the benefits of BoNT‐A treatment outweigh its disadvantages. The trial duration was 12?weeks and thereafter patients were followed for 1?year.