Upper-limb Active Function and Botulinum Toxin a

This study in an observational, prospective and longitudinal study. The aim of the study is to evaluate the effect of botulinum toxin type A (BTX) injections into the elbow flexors on the reduction of spastic co-contractions (spastic co-contraction index, SCCI) during an active elbow extension in chronic post-stroke patients.TBA injections are performed as part of routine care

BTX is a valuable treatment in the management of the focal muscle overactivity (spasticity) following acquired brain injury. If BTX injections reduce spasticity, few studies have examined its effect on the improvement of active function of the upper limb.

Motor task involves the muscles agonists and antagonists by phenomena of muscular coactivation.

In post-stroke patients, functional cortical reorganization secondary to the phenomena of plasticity leads to a reduced motor selectivity. The increase of muscular coactivation correspond to the spastic cocontraction, which are a little evaluated in clinical practice and research, whereas they appear to have a greater impact than spasticity on limitation of active movement.

This study does not evaluate the efficacy of treatment (BTX injection) but the effect of this treatment on a component of muscle hyperactivity, the spastic cocontraction.

In addition to the 5 follow-up visits, patients have 6 intercurrent visits. These visits are less invasive and include only a clinical assessment with surface EMG registration. These evaluations will evaluate the efficacy and harm effect of BTX on clinical parameters and on the spastic co-contraction index. Five intercurrent visits I1, I2, I3, I4, I5 are perform respectively 2 weeks after T1 and, 3, 6, 9, 12 weeks after T2.

Eligibility Criteria:
Stroke group :

Inclusion Criteria:

* Cortical and/or subcortical ischemic or haemorrhagic stroke for at least 6 months;
* Indication to an injection of BTA in the elbow flexor muscles according to the usual clinical criteria: request of elbow extension improvement with a functional or aesthetic objective;
* Being under prescription of abobotulinum toxin A (DYSPORT®, Ipsen-Pharma);
* Ability of active elbow extension\> 20 degrees;
* Limitation of active movement of elbow extension \> 15 degrees or decreased or 50% decrease in the active elbow extension rate;
* Patients who have never been treated with BTX or only a first injection that having targeted the elbow flexors more than 4 months ago;
* Age\> 18 years;
* Signature of informed consent;
* Subject affiliated to the social security coverture.

Exclusion Criteria:

* Passive limitation of elbow extension \> 30 degrees;
* Pain during active movements of elbow flexion/extension;
* Cognitive disorder with limited comprehension of three basic instructions (like the test of the 3 papers of the MMS);
* Evolutionary or decompensated neurological disease;
* Unstabilized epilepsy;
* Anticoagulant treatment with a curative dose or hemostasis disorder that contraindicates intramuscular injections;
* Claustrophobia or metallic foreign bodies contraindicated for MRI;
* General contraindication for botulinum toxin injection: hypersensitivity to the active substance or to one of the excipients, swallowing disorder, chronic respiratory disorders, antecedent of myasthenia or Lambert Eaton syndrome; antecedent of neuromuscular disease; surgery with curarization for less than a month; current treatment with aminoglycoside, aminoquinoline, cyclosporine or anticholinesterase.
* Presence of skin infection or inflammation at the injection site.
* Legal incapacity.
* Pregnant or breastfeeding woman;
* Woman with a desire to become pregnant within 18 months.
* Non-menopausal woman (a postmenopausal state is defined as no menses for 12 months without an alternative medical cause) who does not use one of the following contraceptive methods considered highly effective : intrauterine device, oestroprogestonic contraception or progestogen hormonal contraception associated with inhibition of ovulation, intrauterine hormone-releasing system, or bilateral tubal occlusion.

Control group

* inclusion criteria:

  * Age\> 18 years
  * Signature of informed consent.
* exclusion criteria:

  * History of orthopedic or neurologic disorders;
  * Subject expert in a sport intensively requiring the upper limbs (at least departmental competition level);
  * Legal incapacity.