Predicting Improvement in Writer's Cramp Symptoms following Botulinum Neurotoxin Injection Therapy.
BACKGROUND
Writer's cramp is a specific focal hand dystonia causing abnormal posturing and tremor in the upper limb. The most popular medical intervention, botulinum neurotoxin type A (BoNT-A) therapy, is variably effective for 50-70% of patients. BoNT-A non-responders undergo ineffective treatment and may experience significant side effects. Various assessments have been used to determine response prediction to BoNT-A, but not in the same population of patients.


METHODS
A comprehensive assessment was employed to measure various symptom aspects. Clinical scales, full upper-limb kinematic measures, self-report, and task performance measures were assessed for nine writer's cramp patients at baseline. Patients received two BoNT-A injections then were classified as responders or non-responders based on a quantified self-report measure. Baseline scores were compared between groups, across all measures, to determine which scores predicted a positive BoNT-A response.


RESULTS
Five of nine patients were responders. No kinematic measures were predictably different between groups. Analyses revealed three features that predicted a favorable response and separated the two groups: higher than average cramp severity and cramp frequency, and below average cramp latency.


CONCLUSIONS
Non-kinematic measures appear to be superior in making such predictions. Specifically, measures of cramp severity, frequency, and latency during performance of a specific set of writing and drawing tasks were predictive factors. Since kinematic was not used to determine the injection pattern and the injections were visually guided, it may still be possible to use individual patient kinematics for better outcomes.
Lawson Health Research Institute, London, ON, Canada.
Mallory
M
Jackman
Faculty of Electrical Engineering, K. N. Toosi University of Technology, Tehran, Iran.
Mehdi
M
Delrobaei
Department of Electrical and Computer Engineering, Bonab University, Bonab, East Azerbaijan, Iran.
Fariborz
F
Rahimi
Department of Electrical and Computer Engineering, Western University, London, ON, Canada.
S Farokh
SF
Atashzar
Department of Electrical and Computer Engineering, Western University, London, ON, Canada.
Mahya
M
Shahbazi
Lawson Health Research Institute, London, ON, Canada; Department of Electrical and Computer Engineering, Western University, London, ON, Canada.
Rajni
R
Patel
Lawson Health Research Institute, London, ON, Canada; Department of Clinical Neurological Sciences, Western University, London, ON, Canada.
Mandar
M
Jog
Writer’s cramp; botulinum toxin; focal hand dystonia; kinematics