Mobile intraoperative CT-assisted frameless stereotactic biopsies achieved single-millimeter trajectory accuracy for deep-seated brain lesions in a sample of 7 patients

Background Brain biopsies are crucial diagnostic interventions, providing valuable information for treatment and prognosis, but largely depend on a high accuracy and precision. We hypothesized that through the combination of neuronavigation-based frameless stereotaxy and MRI-guided trajectory planning with intraoperative CT examination using a mobile unit, one can achieve a seamlessly integrated approach yielding optimal target accuracy. Methods We analyzed a total of 7 stereotactic biopsy trajectories for a variety of deep-seated locations and different patient positions. After rigid head fixation, an intraoperative pre-procedural scan using a mobile CT unit was performed for automatic image fusion with the planning MRI images and a peri-procedural scan with the biopsy cannula in situ for verification of the definite target position. We then evaluated the radial trajectory error. Results Intraoperative scanning, surgery, computerized merging of MRI and CT images as well as trajectory planning were feasible without difficulties and safe in all cases. We achieved a radial trajectory deviation of 0.97 ± 0.39 mm at a trajectory length of 60 ± 12.3 mm (mean ± standard deviation). Repositioning of the biopsy cannula due to inaccurate targeting was not required. Conclusion Intraoperative verification using a mobile CT unit in combination with frameless neuronavigation-guided stereotaxy and pre-operative MRI-based trajectory planning was feasible, safe and highly accurate. The setting enabled single-millimeter accuracy for deep-seated brain lesions and direct detection of intraoperative complications, did not depend on a dedicated operating room and was seamlessly integrated into common stereotactic procedures.

Transcranial brain stimulation and structural MRI

Non-invasive transcranial brain stimulation (NTBS) benefits in multiple ways from structural magnetic resonance imaging (sMRI). Individual structural brain scans can be used to guide spatial targeting with frameless stereotaxy. For instance, sMRI informed transcranial magnetic stimulation (TMS) enables personalized cortical mapping aligned to the individual gyral anatomy. Segmented sMRI scans increase the accuracy and robustness of computational dosimetry approaches which are key to standardize the individual dose across individuals, mapping the NTBS induced electrical fields onto the individual brain. Several sMRI modalities can be used to identify macro and microstructural features that are related to the physiological and behavioral effects of NTBS. Structural MRI before NTBS can identify interindividual variations in brain structure that influence NTBS outcomes, including disease or age related anatomical changes. Repeated structural MRI measurements can trace NTBS induced changes in regional macro and microstructure. NTBS based functional markers can be combined with MRI based structural markers to predict disease progression or recovery in individual patients.

How precise are oral splints for frameless stereotaxy in guided ear, nose, throat, and maxillofacial surgery: a cadaver study

Background Computer-assisted surgery optimises accuracy and serves to improve precise surgical procedures. We validated oral splints with fiducial markers by testing them against rigid bone markers. Methods We screwed twenty bone anchors as fiducial markers into different regions of a dried skull and measured the distances. After computed tomography (CT) scanning, the accuracy was evaluated by determining the markers’ position using frameless stereotaxy on a dry cadaver and indicated on the CT scan. We compared the accuracy of chairside fabricated oral splints to standard registration with bone markers immediately after fabrication and after a ten-time use. Accuracy was calculated as deviation (mean ± standard deviation). For statistical analysis, t test, Kruskal-Wallis, Tukey's, and various linear regression models, such as the Pearson's product–moment correlation coefficient, were used. Results Oral splints showed an accuracy of 0.90 mm ± 0.27 for viscerocranium, 1.10 mm ± 0.39 for skull base, and 1.45 mm ± 0.59 for neurocranium. We found an accuracy of less than 2 mm for both splints for a distance of up to 152 mm. The accuracy persisted even after ten times removing and reattaching the splints. Conclusions Oral splints offer a non-invasive indicator to improve the accuracy of image-guided surgery. The precision is dependent on the distance to the target. Up to 150-mm distance, a precision of fewer than 2 mm is possible. Dental splints provide sufficient accuracy than bone markers and may opt for higher precision combined with other non-invasive registration methods.

Globus Pallidus Internus Deep Brain Stimulation Using Frame-Based vs. Frameless Stereotaxy in Dystonia: A Single-Center Experience

Objective: Bilateral globus pallidus internus deep brain stimulation (GPi-DBS) is an established and effective therapy for primary refractory dystonia. However, the comparison of frameless vs. frame-based DBS surgery technique is still controversial. This retrospective study aims to compare the clinical outcome of two GPi-DBS surgical techniques for patients affected by primary generalized or multi-segmental dystonia.Methods: For lead's stereotaxic placement, 10 patients underwent frame-based surgery and the other 10 subjects DBS surgery with a frameless technique. Clinical features were evaluated at baseline and 6 and 12 months after surgery by means of the Burke–Fahn–Marsden Dystonia Rating Scale.Results: Frame-based GPi-DBS and frameless stereotaxic group revealed a comparable clinical outcome with no surgical complications.Conclusions: Frameless technique is safe and well-tolerated by patients and showed similar effectiveness of the frame-based stereotaxic surgery during GPi-DBS for primary dystonia. Notably, it could be a valid alternative solution because of the great advantage in improving the patient's discomfort during awake surgery.

A Novel Therapeutic Approach for Cranial Fasciitis Utilizing Frameless Stereotaxy

Cranial fasciitis is a rare cause of a painless, progressive skull mass in the pediatric population, having been described in only 80 cases in the literature to-date. While the etiology remains unknown, the pathogenesis is thought to be a reactive process causing a non-neoplastic fibroblastic proliferation arising from the deep fascia or periosteum of the cranium. Accurate diagnosis may be delayed due to the lack of physical signs and symptoms on presentation, as well as equivocal imaging for the other lesions included in the differential diagnosis. Importantly, in the case of cranial fasciitis, involved tissue is hard to decipher from normal tissue in the cranium, and margin recommendations have not yet been made clear in the current literature. Herein, we present a case of confirmed cranial fasciitis in a 2-year-old female patient in whom frameless stereotaxy was used intraoperatively to determine the extent of the lesion and ensure adequate resection and minimize recurrence risk.

Frame-based versus frameless stereotactic brain biopsies: A systematic review and meta-analysis

Background: Stereotactic brain biopsy techniques have been a focus of rapid technological innovation. The recent advent of frameless stereotaxy has invited the question of whether it can provide the same diagnostic yield as frame-based techniques, without increasing risk of harm to patients. The goal of this meta-analysis was to compare each of these techniques in terms of yield and safety. Methods: We independently searched four databases for English studies comparing frameless and frame-based stereotactic brain biopsies. Our primary outcome was biopsy diagnostic yield. Our secondary outcomes included mortality, morbidity (e.g., symptomatic postbiopsy intracranial hemorrhage, asymptomatic postbiopsy intracranial hemorrhage, new postbiopsy neurological deficit, and postbiopsy seizure), and frequency of repeat biopsy. We calculated pooled estimates and relative risks for dichotomous outcomes using Review Manager 5.3, with corresponding 95% confidence intervals. Results: A total of 3256 stereotactic brain biopsies (2050 frame based and 1206 frameless), from 20 studies, were included in our final analysis. The results did not demonstrate any significant difference between the two stereotactic systems in terms of diagnostic yield (risk ratio [RR] 1.00, 95% confidence interval [CI] 0.99–1.02, P = 0.64, I2 = 0%). The only significant difference was the increased frequency of asymptomatic hemorrhages in the frameless group (RR 1.37, 95% CI 1.06–1.75, P = 0.01, I2 = 0%). Application of Grading of Recommendations Assessment, Development, and Evaluation to the results yielded very low quality of all outcomes. Conclusion: Based on very low-quality evidence, both frame-based and frameless stereotaxy are safe and effective for biopsy of intracranial tumors. Further study of patient preference and cost comparing analysis is required to identify if either modality should be preferred.

Mini-Tubular Access Surgery: A Single Surgeon's 12 Years in the Corridors of the Neuroaxis

Background Tubular approach surgery now includes complex spinal and cranial procedures. Aided by modified instrumentation and frameless stereotaxy, minimal access surgery is being offered for a growing array of neurosurgical conditions. Methods This article explores the flexibility and adaptability of the tubular retractor system for multiple indications by highlighting the 12-year experience of the primary surgeon using a tubular retractor system reported for the entire neuroaxis including intracranial, foramen magnum, and the craniocaudal extent of the spine for intra- and extradural pathologies. For this article we have not analyzed our experience with degenerative spinal disease. Patient characteristics, pathology, resection results, length of hospital stay, and complications are discussed. Results From August 2005 through March 2017, 538 patients underwent neurosurgical procedures with mini-tubular access. Of these, the 127 patients who underwent mini-tubular access operations for nontraditional indications are discussed here. There were 65 women and 61 men with an average age of 53.5 years. The cases by anatomical location are as follows: 27 cranial cases, 11 foramen magnum decompressions, and 89 for spinal indications. The cranial pathologies included primary and metastatic tumors. The spinal pathologies included intra- and extradural spinal tumors, spina bifida occulta, syringomyelia, and other cystic lesions in the spine. In the vast majority of the patients where gross total resection was the goal, it was achieved. The mean length of stay was 2.94 days. Conclusions This report demonstrates that mini-tubular access surgery can be adapted to pathologies in the entire neuroaxis with outcomes that are comparable with open techniques. Limited tissue dissection, smaller incisions, and limited bone resection make the mini-tubular access approach a desirable option when feasible. Greater experience with all of these techniques is needed before the definitive status of these procedures in the neurosurgical armamentarium can be demonstrated.

Feasibility and performance of a frameless stereotactic system for targeting subcortical nuclei in nonhuman primates

OBJECTIVEDeep brain stimulation (DBS) is an effective therapy for different neurological diseases, despite the lack of comprehension of its mechanism of action. The use of nonhuman primates (NHPs) has been historically important in advancing this field and presents a unique opportunity to uncover the therapeutic mechanisms of DBS, opening the way for optimization of current applications and the development of new ones. To be informative, research using NHPs should make use of appropriate electrode implantation tools. In the present work, the authors report on the feasibility and accuracy of targeting different deep brain regions in NHPs using a commercially available frameless stereotactic system (microTargeting platform).METHODSSeven NHPs were implanted with DBS electrodes, either in the subthalamic nucleus or in the cerebellar dentate nucleus. A microTargeting platform was designed for each animal and used to guide implantation of the electrode. Imaging studies were acquired preoperatively for each animal, and were subsequently analyzed by two independent evaluators to estimate the electrode placement error (EPE). The interobserver variability was assessed as well.RESULTSThe radial and vector components of the EPE were estimated separately. The magnitude of the vector of EPE was 1.29 ± 0.41 mm and the mean radial EPE was 0.96 ± 0.63 mm. The interobserver variability was considered negligible.CONCLUSIONSThese results reveal the suitability of this commercial system to enhance the surgical insertion of DBS leads in the primate brain, in comparison to rigid traditional frames. Furthermore, our results open up the possibility of performing frameless stereotaxy in primates without the necessity of relying on expensive methods based on intraoperative imaging.