Inclusion Criteria- Age 18 to 80 years.
- Hemiplegia sequelae of stroke
- Spasticity of the triceps surae listed at least 1 + / 4 on the modified Ashworth scale
- Ability to give written consent
Exclusion Criteria- Injection of botulinum toxin older than 3 months
- Patient who has already received ultrasound-guided injection of botulinum toxin
- Indication of botulinum toxin injection in other muscle groups in the lower limb than triceps surae
- Swallowing impairment
- Ongoing AVK anticoagulation treatment with INR greater than 3 during one week before randomization.
- Ongoing treatment by aminoglycosides
- General anesthesia with injection of curare planned during the participation in the protocol
- Wearing a pacemaker
- History of ankle arthrodesis
- Other cons-indication for botulinum toxin injection: myasthenia gravis, pregnancy, lactation.