A modified stereotactic frame as an instrument holder for frameless stereotaxis: Technical note

From imaging to precision: low cost and accurate determination of stereotactic coordinates for brain surgery Sapajus apella using MRI

The capuchin monkey (Sapajus apella), a New World monkey species, exhibits prominent characteristics that make it an ideal model for neuroscience research. These characteristics include its phylogenetic traits, telencephalization coefficient, anatomical structures and pathways, genetic profile, immune responses, cognitive abilities, and complex behavioral repertoires. Traditionally, methodologies for stereotactic neurosurgery in research models have relied on the use of brain atlases. However, this approach can lead to errors due to the considerable variation in brain size and shape among individual monkeys. To address this issue, we developed a protocol for deriving individual coordinates for each monkey using a straightforward and relatively inexpensive method involving MRI imaging. Our protocol utilizes a specially designed, 3D-printed stereotactic head-holder that is safe to use with an MR magnet, non-invasive placement of fiducial markers, and post-processing with open-source software. This approach enhances MRI data visualization, improves anatomical targeting, and refines the design of neurosurgical experiments. Our technique could also prove beneficial in other areas of neuroscience research that require accurate calculation of stereotaxic coordinates. Furthermore, it could be useful for other nonhuman primate species for which brain atlases are typically unavailable.

Use of Frameless Stereotactic Navigation System Combined with Intraoperative Magnetic Resonance Imaging and 5-Aminolevulinic Acid

OBJECTIVE

We have described the integrated use of a neuronavigation-guided system for frameless stereotaxy (VarioGuide [Brainlab AG, Munich, Germany]) with intraoperative magnetic resonance imaging (iMRI) and 5-aminolevulinic acid (5-ALA) and report the advantages and disadvantages that the use of these tools together can have in the treatment of various types of intracerebral lesions.

METHODS

After the skin incision, creation of a burr hole at the entry point, and dura opening, the VarioGuide procedure was started. Initially, the wizard software will require positioning of the stereotactic arm over the burr hole and provides feedback regarding the correct position. The procedure is performed in an iMRI theater furnished with a surgical microscope (Kinevo [Carl Zeiss AG, Oberkochen, Germany]) supplied with a violet-blue excitation light for 5-ALA fluorescence. At the end of the surgery, iMRI was performed. We present 2 exemplary cases to describe the application and workflow of these tools.

RESULTS

When used for traditional biopsy, the possibility of performing a new iMRI scan could be of paramount importance because the brain shift can be compensated for and an alternative trajectory can be calculated from the new images and fiber tracking reconstruction. The fluorescence of the tissue sample examined under the microscope filter can provide immediate information about the nature of the lesion, allowing for the possibility of converting the procedure to open craniotomy and tumor removal.

CONCLUSION

The use of combination frameless stereotaxy with iMRI and 5-ALA has shown benefits in terms of safety and precision. Moreover, the use of these tools can simplify tumor removal after simple biopsy, widening the spectrum of indications.

Accuracy of VarioGuide Frameless Stereotactic System Against Frame-Based Stereotaxy: Prospective, Randomized, Single-Center Study

INTRODUCTION

Frameless stereotactic brain biopsy systems are widely used today. VarioGuide (VG) is a relatively novel frameless system. Its accuracy was studied in a laboratory setting but has not yet been studied in the clinical setting. The purpose of this study was to determine its accuracy and diagnostic yield and to compare this with frame-based (FB) stereotaxy.

MATERIAL AND METHODS

Overall, 53 patients (33 males and 20 females, 60 ± 15 years old) were enrolled into this prospective, randomized, single-center study. Twenty-six patients were randomized into the FB group and 27 patients into the VG group. Real trajectory was pointed on intraoperative magnetic resonance. The distance of the targets and angle deviation between the planned and real trajectories were computed. The overall discomfort of the patient was subjectively assessed by the visual analog scale score.

RESULTS

The median lesion volume was 5 mL (interquartile range [IQR]: 2-16 mL) (FB) and 16 mL (IQR: 2-27 mL) (VG), P = 0.133. The mean distance of the targets was 2.7 ± 1.1 mm (FB) and 2.9 ± 1.3 mm (VG), P = 0.456. Mean angle deviation was 2.6 ± 1.3 deg (FB) and 3.5 ± 2.1 deg (VG), P = 0.074. Diagnostic yield was 93% (25/27) in VG and 96% (25/26) in FB, P = 1.000. Mean operating time was 47 ± 26 minutes (FB) and 59 ± 31 minutes (VG), P = 0.140. One minor bleeding was encountered in the VG group. Overall patient discomfort was significantly higher in the FB group (visual analog scale score 2.5 ± 2.1 vs. 1.2 ± 0.6, P = 0,004).

CONCLUSIONS

The VG system proved to be comparable in terms of the trajectory accuracy, rate of complications and diagnostic yield compared with the "gold standard" represented by the traditional FB stereotaxy for patients undergoing brain biopsy. VG is also better accepted by patients.