Use of Analgesic Treatment to Reduce Signs of Pain in Patients With Disorders of Consciousness.

Inclusion Criteria: * Have had an acquired brain injury with a loss of consciousness \> 28 days (patients) or have no history of previous brain injury (healthy controls) * Legally authorized surrogate available to provide informed consent. * Diagnosis of vegetative/unresponsive (VS/UWS) or minimally conscious state (MCS) or emergence of the minimally conscious state without communication (eMCS; as defined by the CRS-R, see above). * Medically stable (i.e., no systemic illness or disease). * Patients with NCS-R score during mobilization above or equal to the previously determined cut-off score or NCS-R scores during mobilization equivalent to NCS-R score obtain during nociceptive stimulation will be included in the second phase of the study (i.e. D1 and D2). Exclusion Criteria: * History of developmental, neurologic, or major psychiatric disorder resulting in functional disability. * Contraindication or unwillingness to discontinuing sedating and centrally-active drugs (benzodiazepine, long-acting sedating drugs) within 48 hours of assessment. * Upper limb contusions, fractures or flaccid paralysis. * Uncontrolled epilepsy and already on level 1 drugs