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

The study will be performed within one week (i.e, 7 days) and consists of two phases: * Phase 1 "Patients selection (D0)": Patients will be assessed by the NCS-R during experimental stimulation (rest, tactile, noxious) and mobilizations (physiotherapy). Patients with potential pain will be included in the phase 2. * Phase 2 "Analgesic administration (D1 and D2)": double-blind placebo-controlled randomized clinical trial on potential responders identified in phase 1. A medical doctor of our team will suggest to the physician in charge to prescribe the dedicated medication. One placebo and one real treatment will be administered on day 1 and 2 by the nurses at least half-hour before the physiotherapy. Randomization between day 1 and 2 will be applied at that time. For each day of phase 1 and 2, several assessments will be performed: NCS-R, CRS-R and spasticity assessment.