Improvement of image guided surgery systems requires a better anticipation of the surgical procedure. This anticipation may be provided by a better understanding of surgical procedures and/or the use of information models related to neurosurgical procedures. We are introducing a generic model of surgical procedures in the context of multimodal image-guided craniotomies. The basic principle of the model is to break down the surgical procedure into a sequence of steps defining the surgical script. Each step is defined by an action; the model assigns to each surgical step a list of image entities extracted from multimodal preoperative images (anatomical and/or functional images) which are relevant to the performance of that particular step. The model has been built in two phases: creation and consolidation. Besides, a planning software prototype based on the generic model has been built. The resulting generic model is described by an UML class diagram and textual description. Some initial benefits of this approach can already be outlined: improvement of multimodal information management, enhancement of the preparation and the guidance of the surgical act.