Seven BBB opening session will be performed at a bi-monthly rate focusing on the left supramarginal gyrus, a cortical structure known to be affected by both amyloid and tau lesions early on during the evolution of the disease. All adverse events induced by surgery itself or by the LICU will be recorded. Amyloid ß and Tau lesion load will be evaluated benefiting from the PET-MRI that allows to clearly evaluate fine changes in SUVR taking into account loco-regional cortical specificity (cortical thickness). PET image analysis.