Communication is an important act in the development and empowerment of human beings. Through language, humans communicate their needs, desires, moods... Unfortunately, many physical and mental disabilities deprive some people of such communication means. Nowadays various Augmentative and Alternative Communication (AAC) systems exist in order to help people with disabilities. Virtual keyboards are the most common AAC systems for physical disabilities. Concerning mental disability, there are tools based on pictograms. This paper is divided into two parts. First, we put forward a critical review of various AAC systems with a focus on users with athetoid cerebral palsy. Second, the paper presents work in progress concerning a communication system for such users.