The pig model in brain imaging and neurosurgery.

The pig model is increasingly used in the field of neuroscience because of the similarities of its brain with human. This review presents the peculiarities of the anatomy and functions of the pig brain with specific reference to its human counterpart. We propose an approximate mapping of the pig's cortical areas since a comprehensive description of the equivalent of Brodmann's areas is lacking. On the contrary, deep brain structures are received more consideration but a true three-dimensional (3D) atlas is still eagerly required. In the second section, we present an overview of former works describing the use of functional imaging and neuronavigation in the pig model. Recently, the pig has been increasingly used for molecular imaging studies using positron emission tomography (PET). Indeed, the large size of its brain is compatible with the limited spatial resolution of the PET scanner built to accommodate a human being. Similarly, neuronavigation is an absolute requirement to target deep brain areas in human and in pig since the surgeon cannot rely on external skull structures for zeroing the 3D reference frame. Therefore, a large body of methodological refinements has been dedicated to image guided surgery in the pig model. These refinements allow now a millimetre precision: an absolute requirement for basal nuclei targeting. In the third section, several examples of ongoing studies in our laboratory were presented to illustrate the intricacies of using the pig model. For both examples, after a brief description of the scientific context of the experiment, we present, in detail, the methodological steps required to achieve the experimental goals, which are specific to the porcine model. Finally, in the fourth section, the anatomical variations depending on the breed and age are discussed in relation with neuronavigation and brain surgery. The need for a digitized multimodality brain atlas is also highlighted.