Writer's cramp: the experience with botulinum toxin injections in 25 patients.

Twenty-five writer's cramp patients have been attending the Movement Disorder Clinic at the Division of Neurology, Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok during three years period (between January 1988 - January 1991). There were 17 male subjects and the male to female sex ratio was 2.125:1. The mean age of the patient was 36.80 (SD 10.21) years with the range of 18-60 years. The mean duration of illness of all patients was 5.88 (SD 7.14) years with the range of 1 to 30 years. Eighteen patients (72.0%) were classified as simple writer's cramp and seven patients (28.0%) were dystonic writer's cramp. The mean age of the patients of both groups was not different while the duration of illness in the dystonic group was statistically significantly longer than the simple group, i.e. 12.0 (SD 12.1) versus 3.9 (SD 3.1) years. Fourteen patients (56%) had associated pain during writing and 6 patients (24%) had hand tremor. All patients were right handed and had a history of various pharmacological treatments without any consistent benefit. They included muscle relaxants, tranquillisers, antiepileptic drugs, and betablockers. Fourteen patients from 17 available history records (82.4%) had been spending at least 4-10 hours writing each day. Twenty-one patients (84%) had botulinum toxin injections, 40-80 international mouse units were given in 2-4 divided doses over the overactive forearm muscles observed during writing without the electromyographic glidance. There was no loss to the follow-up. Fourteen of the 21 subjects (66.7%) showed definite improvement in hand writing, 4 patients (19.0%) improved minimally and 3 patients (14.3%) revealed no improvement. Arm pain in all 12 patients associated during writing was abolished after the injections. There were complications in 7 patients (33.3%) presented as transient finger drop (5 patients, 23.8%) and easily fatigued arm (2 patients, 9.5%). These preliminary results confirm that botulinum toxin injections is a successful treatment for many patients with writer's cramp without performing complex electromyographic recordings while the patients are writing. The constraints of this treatment are its high cost (i.e. 1 vial of 100 units costs 300 US dollars) and its benefit lasts for only 4-6 months.