Current techniques for implanting hardware in deep brain structures of non-human primates are inaccurate or cumbersome. Orthogonal stereotactic frames inadequately hold the skull using ear bars. Registration is performed using surface landmarks and standard stereotactic atlases and this may lead to significant errors in the placement of electrodes and catheters. It is also difficult to accurately define oblique trajectories. Frameless systems are employed to improve registration and targeting but are limited by a dependence between the location of the target site and the entry point in the skull. We have developed an arc based stereotactic frame by translating standard technology used in human functional brain surgery. An MRI compatible halo and imaging box is fixed to the animal and a pre-operative MRI is performed. Registration is achieved using the anatomy of deep brain structures. The orthogonal coordinates of each target are then calculated and used as coordinates in the frame. The advantage of this system is that a deep brain target can easily be accessed through any entry site. It also enables precise targeting along predefined trajectories. The main challenges of employing this technology are due to differences in anatomy such as the small size of the rhesus monkey brain compared to the human brain, differences in calvarial and facial skull shape, and increased cranial and cervical muscle bulk. This arc based stereotactic frame enables the rapid and simple implantation of hardware in a minimally invasive manner and will result in novel experimental paradigms.
Arc Based Stereotactic Surgery for Precise Implantation of Hardware into Brain Structures of Non-human Primates