The aim of this study is to confirm the efficacy and safety of the intra-articular injection of BT-A in a multicentric double blind randomised study. For this purpose intra-articular injection of BT-A will be compared with the intra-articular steroid injection that is the current "gold standard" for the treatment of HSP.

Shoulder pain is one of the most common complications of stroke. In fact, it occurs up to 70% of stroke victims. Post-stroke shoulder pain impacts negatively on daily activities. Moreover, it interferes with the rehabilitation process, is related to poor quality of life and has been associated to a worse outcome and to prolonged hospitalization.The aetiology of post-stroke HSP is uncertain, although it has been associated with various factors: joint disorders, capsulitis adhesive, subluxation of the head of the humerus, rotator cuff tendons injuries and spasticity of surrounding muscles. Clinicians use a wide variety of approaches to treat post-stroke HSP, although none has yet been proven effective. Correct positioning and careful handling of the hemiplegic limb are believed to prevent HSP. Physiotherapy alone does not seem to be effective for this complication. Capsulitis adhesive can be successfully treated with corticosteroid injections in the shoulder. However, despite many randomized controlled trials of corticosteroid injections for shoulder pain, their effects remain controversial. The large number of interventions and the lack of consensus about their effectiveness suggest that the aetiology is poorly understood and hence its treatment remains to be established. Intramuscular injections of botulinum toxin type A (BT-A) have also been demonstrated to reduce HSP. The mechanism whereby intramuscular inoculation of BT-A reduces pain may include a muscle relaxant effect and inhibition of the release of neurotransmitters by sensory neurons. Nevertheless, this approach has some limitations: it is probably more effective in muscular than in articular pain and it may be influenced by the muscles affected and site of injection. Intra-articular injection of BT-A has recently proven safe and effective in the treatment of refractory joint shoulder pain caused by chronic arthritis. The mechanisms by which it exerts this effect are not known, but could include inhibition of the release of pain peptides from nerve terminals and sensory ganglia, and anti-inflammatory and anti-glutaminergic effects.

Inclusion Criteria:

• Patients with hemiparesis and shoulder pain due to first stroke (ischemic or hemorrhagic) admitted in a rehabilitative department to carry out a standard post-acute rehabilitative program
• Pain score of 45 or greater on a 0-100 mm pain visual analog scale (VAS; 0 = no pain, 100 = worst possible pain)
• Duration of HSP for at least one month
• Pain refractoriness to conventional treatment i.e. common analgesics (such as paracetamol and NSAIDs), slings, strapping and handling of the arm, functional electrical stimulation of shoulder muscles

Exclusion Criteria:

• Significant spasticity in the upper shoulder joint, defined as a score of 2 or more at the modified Ashworth scale
• History of shoulder pain or shoulder diseases.
• History of neurological diseases (i.e. Parkinson disease, dystonia).
• History of botulinum toxin treatment