This chapter presents the rich body of recent works in persons with disabilities (PWD) area, with a special focus on a few teams in various parts of the world who achieved standards of performance that would allow these systems to truly benefit patients in the context of cross-disciplinary care. It focuses on the very specific case of users whose disability is sufficiently severe so as to prevent all communication without assistance from an augmentative and alternative communication (AAC) system, whether verbal or non-verbal. The performance of medical communication brain-computer interface (BCIs) has been proven in a number of clinical trials with patients. The studies on BCIs have exhibited a large variety of techniques and interfaces, with a strong preference for visual interfaces and in particular interfaces based on the P300 wave. Reactive interfaces have occupied a decisive role in the evolution and popularity of BCIs.