Impact of Severe Brain Injury on Neuro-vascular and Endothelial Regulation of Peripheral Microcirculation.

Inclusion Criteria: Healthy volunteers : * Men and women, over 18 years of age * Affiliation to a social security scheme * Signed Consent Patients with Severe Brain Injury : * Male and female, over 18 years of age * Isolated severe brain injury, defined by an initial Glasgow score less than or equal to 8. * Affiliation to a social security scheme * Signed informed consent Severe traumatized patients without associated severe brain injury: * men and women, over 18 years of age * severe trauma, defined by an Injury Severity Score (ISS) ≥ 16. * absence of associated severe brain injury, defined by an initial Glasgow score less than or equal to 8. * affiliation to or beneficiary of a social security scheme * signed informed consent Exclusion Criteria: * Hypersensitivity to lidocaine and/or prilocaine or to amide type local anesthetics or to any of the excipients of the cream. * History of axillary lymph node dissection, trauma or axillary surgery * Prohibited treatments and procedures : * In patients with head trauma: ongoing treatment with systemic vasodilators (calcium channel blocker, milrinone). * In healthy volunteers: no treatment will be authorized other than paracetamol, hormone supplementation (contraceptive pill, hormone therapy, thyroid hormones). * Pregnant, parturient or breastfeeding women * Subject in a period of exclusion from another study, * Person deprived of liberty by judicial or administrative decision, person subject to a legal protection measu…