This study is a multicenter, double-blind, randomized placebo controlled, parallel group, superiority trial in order to test the superiority of intramuscular injections of IncobotulinumtoxinA against placebo using a 1:1 allocation ratio.

After a baseline evaluation, each patient will receive a first injection of IncobotulinumtoxinA or placebo (50:50 randomization) in a double blinding setting. Assessment of the Focal hand dystonia (FHD) will be done at each site by an investigator blinded to the treatment.

A first evaluation of the efficacy will be performed after 6 weeks. After 6 weeks, patients unsatisfied with treatment and wishing to continue the treatment will receive an injection of IncobotulinumtoxinA regardless of the treatment arm they were initially assigned to at baseline. These patients will subsequently be excluded from the study.

A second assessment will be performed after 12 weeks (only for patients not receiving a second injection of IncobotulinumtoxinA at week 6).

Inclusion Criteria:

• Informed Consent as documented by signature
• Age ≥ 18 years
• Focal hand dystonia (FHD). Diagnosis must be made by a neurologist specialized in movement disorder (at least 2 years specific training, all partners listed have at least 2 years training)
• Both idiopathic and secondary FHD are allowed
• Both drug naive subjects and subjects previously treated with other BoNT-A will be included
• Patients must be willing and able to comply with the study procedures
• Female patients of childbearing potential must agree to use an effective method of contraception during the treatment period

Exclusion Criteria:

• Presence of spasticity, or other central sensorimotor lesion of motor system other than dystonia in the affected limb
• Peripheral nerve lesion (diagnosis either clinical or electrophysiological) in the affected limb, for example with a muscle weakness at baseline
• Contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to BoNT-A toxins including IncobotulinumtoxinA
• Doses and schedules of any ongoing treatment with potential confounding drugs such as muscle relaxants (for example Tolperison, Tizinadid, Baclofen, Mestinon, Dantrolen), benzodiazepine, neuroleptics or antidepressants have to be kept unchanged throughout the study and no changes should be made between the first trial injection and the end of study visit at week 12.
• Previous treatment with other BoNT-A less than 3 months before the inclusion in this study
• Women who are pregnant or breast feeding,
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• Participation in another study with investigational drug within the 30 days preceding and during the present study
• Previous enrolment into the current study
• Enrolment of the investigator, his/her family members, employees and other dependent persons
• Severe depression (>29 as measured with the Beck Depression Inventory, see Appendix 8) or other relevant psychiatric disorder
• INR > 2 on the day of injection if the patient is anticoagulated. If INR > 2, the study injection will be delayed until the return to a safer INR.