This paper proposes a new approach to support medical decision making based on the analysis of multidisciplinary clinical discussions, which are becoming routine in hospitals and other health structures. In a medical discussion, participants make important pieces of knowledge explicit, by presenting different opinions, providing evidences that support hypotheses, and possibly arguing about clinical guidelines. However, this knowledge is often lost after the meeting is closed, since only the final decisions are written in patient records. Therefore, a computer-based system is proposed to help physicians manage clinical discussions, analyze them by means of argumentation-based techniques, and arrive, in the long run, at a synthesis of new knowledge fragments useful for future decisions. A preliminary experimentation of the system is presented in the domain of cognitive degeneration diseases.