34th Annual Scientific Meeting proceedings

Introduction

Neurosurgery demands a deep anatomical and physiological knowledge of the nervous system, and also from their protective and covering layers: bone, ligaments, muscle and skin. During the last two centuries, the knowledge of neuroanatomy has allowed us to identify and locate eloquent regions in the central nervous system, their anatomical relationships with adjacent structures, their interconnection pathways and anatomical projection towards the cerebral cortex, the skull and skin, this has allowed us to discover anatomical corridors that give us surgical access to deep regions of the nervous system, avoiding injury to tissues that we must preserve.

Likewise, in addition to developing safer and more efficient surgical accesses for the patient, increasingly less invasive approaches have been developed, both for cranial and spineal surgery, using “key-hole approach” techniques, endoscopic surgery or with tubular minimally invasive approaches

Less invasive surgical approaches allow the manipulation of the nervous tissue to be limited, which, in turn, reduces the risk of injury; however, the concept of minimal invasion itself implies a reduction in the anatomical exposure of the surgical field, which can limit the exposure of “classical” landmarks as well as the space available to manipulate the tissues, increasing the technical difficulty of the procedure, facilitating the possibility of becoming “disoriented” anatomically during prolonged surgeries and increasing the difficulty of teaching. This is where neuronavigation (mainly) and possibly robotics play a very important role in modern surgery, as a support of the anatomical knowledge, which is fundamental.

Neuronavigation

Neuronavigation is the set of computer-assisted technologies used by neurosurgeons to guide or "navigate" within the confines of the skull or vertebral column during surgery. Can be considered as a next step to stereotaxy, although in reality, for some procedures, it does not achieve sufficient precision to replace it. The advent of modern neuro-imaging technologies such as computed tomography (CT) and magnetic resonance imaging (MRI), along with the ever-increasing capabilities of digitalization, computer-graphic modelling and accelerated manipulation of data, made possible the real-time spatial fusion of images of the patient with the created “coordinate system” for the purpose of guiding the surgeon's instrument or probe to a selected target. This, give us the ability to relate the position of a real surgical instrument in our hand or even the microscope's focal point, to the location of the imaged pathology, updated in "real time" in an "integrated operating room", that can be enhanced  with new neuro-imaging technologies (intra-opperative CT or MRI), real-time imaging capabilities (ultrasound), or new technologies to transfer the information in the operating room for 3-D localization, real-time neuro-monitoring, robotics, and new and better algorithms to handle data via more sophisticated computer technology.

Robotics in neurosurgery

Currently, when referring to robotic or robotic surgery in neurosurgery, we are really talking about robotic “assistants” to surgery, since they are robotic arms that assists the surgeon during the procedure, not devices through which perform the surgery. Using these devices, and always associated with state-of-the-art navigation systems, the trajectories of our approaches can be programmed in the robot to: hold endoscopes or working channels to implant deep brain recording or stimulation electrodes, for spinal decompressions or screw implantation.

Navigation in cranial surgery

Neuronavigation has facilitated cranial surgical through “key-hole approaches”, it has increased the safety of surgical procedures by helping to locate critical structures (such as arteries or veins) before even seeing them within the surgical field, or, once segmented within the navigator, locate eloquent cortical or deep structures or the lesion itself, to know the distance margin to them or to quantify possible tumor remains.

Navigation and robotic in spine Surgery

Total neuronavigation in spinal surgery has a series of advantages: it increases the precision of the surgery by optimizing the size and position of the implant, which results in greater safety for the patient, it reduces radiation exposure of the surgical team, it can accelerate workflow, improve results in oncological surgery, avoid complications in non-instrumented surgery, facilitate education and can eliminate the need for reintervention to reposition a malpositioned implant. In addition to the neuronavigator, there is a 3D image acquisition system using CT or CT-alike, for patient registration and subsequent intraoperative control. This neuronavigation system with intraoperative CT can be complemented with a robotic arm, which allows, once the coordinates and trajectories have been selected on the image study carried out in-situ and through the navigator, to be directed “autonomously” towards the entry points and trajectories designed, to hold tubular dissectors or working channels through which to place implants.

Limitations

The main limitation of neuronavigation systems is the risk of loss of calibration, as they depend on an external reference “frame” or “star” adjacent to the patient, which may be fixed to him (spinous process, iliac crest) or to its support (craniostat) by means of an articulated arm or clamp, other limitation is due to operating with a previously acquired radiological image, which is not updated in-vivo as the surgery progresses: the soft tissues are displaced, resected or swollen, which It gives rise to a phenomenon known as “shifting” that generates a loss of correlation between our surgical field and the radiological image loaded in the navigator. These phenomena must be known and recognized by the surgeon so that, once identified, can be taken into account when continuing surgery or corrected using intraoperative support or recording techniques: anatomical recalibration, navigated ultrasound recalibration, or intraoperative CT or MRI registration.