In the context of an insufficiency of clinical results for cortical stimulation in treatment of brachial plexus post-avulsion pains, one of the possibility for failure is the bad pre-surgery mapping of the area to stimulated bu the usual methods (PEM et fMRI). This purpose of this study is to realise a precise mapping of the primary motor cortex post brachial plexus avulsion.

The principal endpoints is to identify and test the reliability of a muscular marker for which the cortical representation is localized immediately next to the superior member area. Several muscles of cephalic, cervical and chest area will be investigate.

The methods used will be mono-shock transcranial magnetic stimulation (mTMS) and functional MRI.

Concerning mTMS, several methods will be tested: best position on the scalp, realisation of outputs maps with extreme points average method, with mass center method.

Concerning fMRI studies, the above paradigms will be checked: imaginary movements of hand, blow up and down abdomen, eyes winking.

Statistical tests will confirm the best muscle candidate and will permit to evaluate the reliability of the method.

Inclusion Criteria:

• For all groups: informed consent, social insurance
• For group 1 "painful BPA": consulting to the Nantes'UH for pain of BPA, EVA≥4, neurological deficiency partial or total
• For group 2 "painless BPA": EVA<4, neurological deficiency partial or total, matching with group 1 on the neurological deficiency
• For group 3 "Healthy": matching with group 1 on age ±10 years

Exclusion Criteria:

• No informed consent
• Medical history of epilepsy
• Pregnant women
• Contra-indication to MRI