Impact of Hypno-analgesia on Pain During a Lumbar Puncture for Diagnosis of Alzheimer's Disease

The main objective was to assess whether the use of hypnoanalgesia technic during the LP procedure comparing to commun procedure reduce the pain of the patient evaluated by the hetero-evaluation ALGOPLUS scale. Secondary objectives were to evaluate the differences between the hypno-analgesia and the helping relationship on: * pain assessed by the Simple Verbal Scale (EVS); * pain assessed by the Visual Analog Scale (EVA); * pain and stress measured by conductance analysis; * the anxiety score assessed by a STAI self-assessment questionnaire (State-Trait Anxiety Inventory, STAI-Y); * the rate of failure during the LP procedure. Methodology : A monocentric randomized controlled, open-label (with an evaluation of the blind randomization of the randomization arm) with two parallel arms: * the arm named "hypno-analgesia + EMLA patch" = cutaneous anesthesia associated with hypno-analgesia. * the arm called "helping relationship + EMLA patch" = cutaneous anesthesia associated with a helping relationship The estimated number of patients was 100. Analysis of the primary outcome measure: The score of the ALGOPLUS scale will compared between the two groups of patients using the Chi2 test after checking the validity conditions of the test. The project will last 36 months and the duration of the inclusions 24 months. The LP will be carried out during one day of hospitalization as part of the diagnosis assessments. No specific follow-up is scheduled.