Predicting Improvement in Writer's Cramp Symptoms following Botulinum Neurotoxin Injection Therapy

Mallory Jackman; Mehdi Delrobaei; Fariborz Rahimi; S Farokh Atashzar; Mahya Shahbazi; Rajni Patel; Mandar Jog

doi:10.7916/D82Z15Q5

Predicting Improvement in Writer's Cramp Symptoms following Botulinum Neurotoxin Injection Therapy

Tremor Other Hyperkinet Mov (N Y). 2016 Sep 3:6:410. doi: 10.7916/D82Z15Q5. eCollection 2016.

Authors

Mallory Jackman¹, Mehdi Delrobaei², Fariborz Rahimi³, S Farokh Atashzar⁴, Mahya Shahbazi⁴, Rajni Patel⁵, Mandar Jog⁶

Affiliations

¹ Lawson Health Research Institute, London, ON, Canada.
² Faculty of Electrical Engineering, K. N. Toosi University of Technology, Tehran, Iran.
³ Department of Electrical and Computer Engineering, Bonab University, Bonab, East Azerbaijan, Iran.
⁴ Department of Electrical and Computer Engineering, Western University, London, ON, Canada.
⁵ Lawson Health Research Institute, London, ON, Canada; Department of Electrical and Computer Engineering, Western University, London, ON, Canada.
⁶ Lawson Health Research Institute, London, ON, Canada; Department of Clinical Neurological Sciences, Western University, London, ON, Canada.

Abstract

Introduction: 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.

Discussion: 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.

Keywords: Writer’s cramp; botulinum toxin; focal hand dystonia; kinematics.