Neuronavigation is a computer-assisted, software-controlled neurosurgical procedure. It is mainly used for operations on the brain or spine. The aim of neuronavigation is to ensure better planning of the operation and better orientation during the operation.
Here you will find further information and selected specialists for neuronavigation.
Neurosurgery is a computer-assisted procedure in neurosurgery. This means that computers are used to assist the surgeon and minimize errors and complications.
In a broader sense, computer-assisted procedures belong to the equipment-based techniques of intraoperative diagnostics. These are diagnostic methods that are used during a surgical procedure. These techniques have become an integral part of everyday neurosurgical practice.
Neuronavigation enables the surgeon to see "more" than the surgical site in front of him. He can see the three-dimensional tissue, nerve and other structures on a monitor. The computer also displays the current position of the microsurgical instruments used. This enables the surgeon to orientate himself precisely.
Synonyms for the term neuronavigation are
The first description of intraoperative navigation goes back to the American neurosurgeon D. Roberts in 1986. At almost the same time, similar systems were developed in Europe (Mösges, Reinhardt) and Japan (Watanabe).
In recent years, the technology has been developed further and further. Neuronavigation is no longer only used in brain tumor surgery. It is becoming increasingly widespread in other disease entities such as
The range of applications and clinical indications for neuronavigation are the same for all systems. The possible sources of error and the limitations of the method are also independent of the individual components selected.
Theclinical purpose of neuronavigation is
The spectrum of intraoperative diagnostics ranges from neuronavigation and intraoperative imaging to intraoperative neurophysiological monitoring. All of these methods represent an improvement in surgical procedures. Their aim is to
Neuronavigation achieves this by increasing spatial orientation options during the surgical procedure. Neurophysiological monitoring provides more functional data from the operated brain areas.
Neuronavigation is based on stereotaxy. This is a procedure for the spatially precise, targeted control of radiotherapy or interventions. Compared to stereotaxy, neuronavigation lacks the
Both methods have the principle of precisely localizing the structures to be treated on the CT or MRI images of a patient in the surgical field. To do this, it is necessary to correlate both coordinate systems, that of the patient and that of the image data. This means that the system must know which point on the image corresponds to which point in reality. This procedural process is called registration (see below).
Figure 1: Performing preoperative referencing to correlate the real neuroanatomy with the virtual image data (MRI): The patient's head is fixed in the head holder. The reference frame is recognized by the camera. A digitizer is used to merge the two coordinate systems pre-/intraoperatively.
Neuronavigation works framelessly. A three-dimensional digitizing instrument (digitizer) serves as a link between the patient's anatomical reference structures and the image data. This digitizer is used to define the individual points within the working space. For example, the position of an instrument tip requires x-, y- and z-coordinates. In this way, the surgical field and the three-dimensional image of the patient are digitized.
In neuronavigation, the patient's image data is available intraoperatively as three-dimensional data sets. The individual points, e.g. inside the skull, are precisely defined in the x, y and z axes. Increasingly powerful computer technology can process and display the data from the digitizer and the huge amounts of image data more quickly.
The individual system components of navigation units in neuronavigation procedures are largely similar:
During neuronavigation, the system continuously evaluates the spatial position and coordinates of the digitizer. It forwards the processed data so that its localization can be displayed on the image data at any time. It is therefore possible to determine the position and display the location of the digitizer at all times during the operation. The digitizer can also be defined intraoperatively via the microscope focus point.
Various systems are used as digitizers in neuronavigation. Optical systems are currently established as a kind of standard in neurosurgery. Infrared or visible light, which is detected by cameras, is used to locate the localization instrument or the surgical microscope.
Magnetic sensor systems are currently experiencing a renaissance. They use the deformation of a magnetic field emitted by the system to determine position. In the meantime, they were hardly ever used.
The choice of method used for neuronavigation ultimately depends on the type of process to be visualized.
For example, a bone-associated process is more likely to be optimally visualized in a CT scan. This applies in particular to spinal neuronavigation. For most indications in tumor surgery, however, the MRI examination plays the greater role. Functional data such as the imaging of speech functions can be implemented more easily here (so-called matching; see also Figure 3).
Regardless of the imaging method chosen, the doctors place markers in the surgical area before the procedure. These markers are used for later registration. In addition, a volume data set of this surgical area, e.g. the skull, is created. A volume data set consists of several images at different heights of the skull, which can later be combined in three dimensions.
The data sets are then transferred to the navigation system. There, in preparation for neuronavigation, registration is carried out using the markers and a 3D image is reconstructed.
The surgeons can then plan the approaches and finally define the tumor boundaries in the data set.
At the start of the operation, the patient is positioned and their head is immobilized. The reference frame is usually attached directly to the headrest (Figure 1). It therefore remains in the correct position in relation to the patient's head during table movements.
The data set is then registered in correlation to the patient. Once both coordinate systems have been compared using the digitizer, neuronavigation can be initiated.
The basis for registration in neuronavigation is the correlation of identical points in both coordinate systems. This is done either by
The accuracy of the registration depends crucially on the intraoperative deviation, which then allows precise localization of the target area during neuronavigation.
Following registration, the navigation system is ready for use.
The surgeon can plan the approach and the size and position of the skull opening. This is important in order to minimize surgical trauma (Figure 2).
In this phase of the procedure, the available image data is usually displayed via the microscope focal point. This then takes over the function of the digitizer (Figure 3). In this way, normal and pathological structures can be differentiated under the microscope. When the imaging signals reach the tumor margins, neuronavigation can be used to check the progress of the operation.
Figure 2: Screenshot of a Stryker-Leibinger navigation in the three spatial axes sagittal, coronal and axial: The brain tumor with a large necrotic component was marked in yellow. The crosshairs show the shortest access route to the center of the lesion. In the 3D view, the tumor contours are projected onto the skin surface of the skull.
Figure 3: Intraoperative navigation with surgical microscope, representation of the process, a sarcomatous tumor, in the axes of the 3D space: In addition, the image data of a functional MRI are underlaid so that functionally important areas for the hand and foot region can be integrated. In addition, electrophysiological monitoring, a motor cortex stimulation (plate electrode), is carried out to reliably define and protect functionally important areas.
Despite numerous innovations, applications such as neuronavigation cannot replace the surgeon's knowledge of neuroanatomy.
Only the neurosurgeon can be responsible for the plausibility of the navigation data and incorrect information in neuronavigation. Known sources of error are
The main weakness of neuronavigation is that the surgeon changes the anatomical structures during the procedure. However, neuronavigation continues to use the previously created images. In other words, the image on the monitor shows an outdated position before the operation.
This error, commonly referred to as brain shift, can be significant. It can only be corrected by using intraoperative imaging, such as MRI or sonography.
Despite the widespread use of neuronavigation in neurosurgery, there is no evidence-based data that it is absolutely necessary.
The working group led by C.R. Wirtz (Wirtz) has carried out a comparative study on the effectiveness of tumor removal without and with the use of neuronavigation. He showed an increase in the radicality of the operation without being able to prove a significantly better result.
There is a broad consensus that neuronavigation should only be used for deep-seated lesions. There are still no forensic consequences of failing to use neuronavigation in neurosurgical procedures. The responsibility of the surgeon also remains unchanged.
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