Botulinum toxin-A injections via electrical motor point stimulation to treat writer's cramp: pilot study.
OBJECTIVE
Writer's cramp describes a task-specific dystonia, in which the act of writing initiates dystonic posturing of the hands. Previous studies have described the efficacy of injections of botulinum toxin type-A (BTX-A) under electromyographic guidance, in which the injected muscle is either voluntarily, or less often, electrically (electrical motor point stimulation, EMPS) activated to ensure that the needle is in the target muscle. We performed an open label, prospective study to assess the efficacy of BTX-A injections, performed with EMPS under electromyographic guidance.


METHODS
Eight patients (seven male and one female) of mean age 44 (range 25-66) were recruited. All had idiopathic writer's cramp. Outcome measures, which included timed writing, objective assessment of dystonia (modified Ashworth scale and a visual analog scale rating) and patient assessment of functional disability, were assessed before injections and at six weeks follow-up.


RESULTS
The total dose of BTX-A injected for writer's cramp ranged from 50 to 130 units, which was less than that reported in previous studies using muscle activation techniques (up to 300 units). Improvements were observed in all outcome measures. Patients reported mild (non-disabling) weakness of injected, but not of uninjected muscles.


CONCLUSIONS
Lower dosages of BTX-A, administered using EMPS, offers the advantages of decreased cost and increased accuracy of targeting, while achieving good outcomes.
Lim
E C H
EC
Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. mdcelch@nus.edu.sg
Quek
A M L
AM
Seet
R C S
RC
D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage* / Q000009:adverse effects; D004185:Disability Evaluation; D004305:Dose-Response Relationship, Drug; D020821:Dystonic Disorders / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006225:Hand / Q000294:innervation / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000139:chemically induced; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation / Q000503:physiopathology*; D009466:Neuromuscular Blocking Agents / Q000008:administration & dosage / Q000009:adverse effects; D009469:Neuromuscular Junction / Q000502:physiology; D017063:Outcome Assessment, Health Care; D010865:Pilot Projects; D011446:Prospective Studies; D016896:Treatment Outcome
D009466:Neuromuscular Blocking Agents; D019274:Botulinum Toxins, Type A