Objective: To study the clinical features in task specific dystonia and its response to botulinum neurotoxin (BoNT) treatment.

Background: Task specific dystonia is rare form of dystonia, which affects usually younger people. It is usually limited to specific tasks in repetitive tasks, most commonly manifested as writer’s cramp (WC) and sometimes as musician’s dystonia.  The treatment choices for task specific dystonia are limited, mostly in selected casesBoNT injections.

Method: We studied the patients with task specific dystonia treated in the university hospitals of Tampere and Helsinki between the years 2007-2016. The following data was collected from patient records: gender, age of onset of dystonia symptoms, response to BoNT and dystonia type.  The sickness allowance data and retirement months were calculated from social insurance institution and pension registry information and compared to age and gender matched controls.

Results: Patient records revealed 117 task specific dystonia patients, of which 26 had musician’s dystonia. The instruments used with musicians were guitar/bass (3), violin (6), piano (5), drums (5), wind instruments (7), of these three had embouchure dystonia.  21 patients had action induced dystonia that was not limited to one task. 19 patients had segmental or multifocal dystonia. The mean age for patients was, 40,8 ± 13,2 years, no significant differences were seen, even though the patients with segmental or multifocal dystonia were slightly younger at the onset of dystonia (35,8 ± 16,3 years). 80% of the patients with WC received BoNT treatment, and 50% having musician’s dystonia, respectively. For all patients, type A BoNT was used. BoNT response was worst in patients with musician’s dystonia (23%), otherwise about 50 % of the patients did benefit of BoNT. The reasons not to receive BoNT treatment were the mild symptoms, fear of side effects or doctor’s previous experiences with similar type of patients.

Conclusion: The response to BoNT in different task specific dystonia was mediocre, but no severe side effects were seen. Musicians had worse response for BoNT than other task specific dystonia. Although the dystonia begun as focal task specific dystonia, in 34% of the patients the dystonia manifestation became more widespread. The dystonia symptom did not reflect in sick allowances, but many patients changed their work functions.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/task-specific-dystonia-and-its-response-to-botulinum-neurotoxin-treatment/