Impact of BrainLab VectorVision Infrared-Based Neuronavigation on Surgical Outcomes in Intracranial Meningioma Patients: A Retrospective Study

Introduction

Meningiomas originate from arachnoid cap cells located on the inner surface of the dura mater [1]. Most meningiomas are benign tumors and are frequently diagnosed incidentally [2]. They can occur anywhere in the central nervous system [3]. The most common intracranial locations are in the cerebral convexity and parasagittal region. Occasionally, they occur outside the central nervous system [4].

Meningiomas are more common in adults than in children, with a prevalence of 37.75 per 100 000. Contrast-enhanced brain magnetic resonance imaging (MRI) is the most commonly used radiological method in the diagnosis of meningioma. Homogenous contrast uptake, regular border, and presence of a dural tail are the most prominent radiological features [5]. The main approach in the treatment of meningiomas is surgery, which is the most effective method for achieving long-term survival, particularly in cases of low-grade meningiomas [6,7]. Surgical complications include venous injury, hematoma, infection, and cerebrospinal fluid (CSF) leakage. Injury to the SSS is an important complication, particularly during parasagittal meningioma resection [3,6].

The surgeon’s experience and the tumor’s vascularization are the most important parameters for achieving gross total resection. Neuronavigation is a device neurosurgeons use to achieve gross total resection of tumors and prevent complications [3,8]. This provides an advantage, particularly in terms of protecting neurovascular structures. It shortens surgery duration by making smaller incisions and craniotomies, with precise localization of the tumor. This also reduces blood loss and increases the surgeon’s confidence [2,7].

The BrainLab VectorVision system is a neuronavigation system that links a freehand probe, tracked by passive sensors, to preoperative images of the patient into a virtual computer image space. Infrared flashes emitted by 2 cameras are reflected by passive marker spheres mounted near the patient’s head and on surgical instruments. The software can calculate the position of a sphere in three-dimensional space using data from both cameras, thus determining the position of the entire instrument [9].

The objective of this study was to examine the efficacy of neuronavigation systems in the surgical treatment of parasagittal and convexity meningiomas.

Material and Methods

ETHICS:

Ethics approval was granted by the local Medical Research Ethics Committee of Ondokuz Mayıs University Clinical Research (Decision no: 2023/373). Written informed consent was obtained from all participants. The data was then collated and analyzed centrally at Ondokuz Mayıs University.

INCLUSION CRITERIA:

This retrospective study analyzed data from 80 patients who underwent surgical treatment for meningioma between 2013 and 2023. The study evaluated the pathology results of patients aged 14–72 years with meningiomas located in the parasagittal and convexity regions, based on the World Health Organization’s (WHO) 2021 Classification of Central Nervous System Tumors. Only patients who underwent preoperative and postoperative contrast-enhanced brain MRI were included.

DATA COLLECTION:

We examined the location of the tumor (parasagittal convexity) and the length and width measurements of the area affected by the tumor on the dura mater. Demographic data, including sex and age, were collected. Complications were recorded in the surgery reports. These complications included instances in which the location of the tumor could not be identified, thereby leading to enlargement of the initial craniotomy and injuries to the SSS. We evaluated cases of an epidural hematoma thicker than 5 mm and the level of epidural hematoma in brain computed tomography (CT) images taken as part of routine postoperative assessment within the first 2 h. Brain MRIs are not routinely conducted within the first 48 h in cases that required total excision, as surgical borders of meningiomas become evident during surgery. Residual evaluation was based on postoperative brain CT images. If the 6-month brain MRI images showed increased residue compared to the postoperative CT scan, it was considered as recurrence. The follow-up period was 6 months.

The surgery report analyzed data on tumor resection, including gross total resection, partial resection, and biopsy, as well as dura and bone excision. The patients were classified using the Simpson classification system. Although different surgeons operated on the patients, they all followed the same surgical protocol using microsurgery. Nevertheless, the retrospective nature of the study and the fact that the operations were performed by different surgeons are limitations. MRI scans for neuronavigation were acquired with a 1.5 Tesla (T) magnet device (Intera; Philips Medical Systems, Best, The Netherlands), with a slice thickness of 1 mm. The neuronavigation system used was the Brainlab infrared-based navigation system (Brainlab Kick; Brainlab AG, Feldkirchen, Germany).

STATISTICAL ANALYSIS:

Data are described as the mean standard deviation for numerical and frequency (percentage) for categorical variables. Nominal variables were compared with chi-square or Fisher’s exact test and the comparisons of the rate of change between 2 groups were tested with an independent sample t test or Mann-Whitney U test, as appropriate. Comparisons between the 2 groups were performed by using the analysis of variance test or Wilcoxon test. Pearson’s correlation coefficient or Spearman’s correlation coefficient was used to measure the strength of the linear relationship between 2 variables. Statistical analyses were performed with SPSS version 21.0 (Chicago, IL). The level of statistical significance was set at P<0.05.

Results

DEMOGRAPHIC FINDINGS OF STUDY POPULATION:

Among the 80 patients evaluated in the study, 36 (45%) had convexity meningiomas and 44 (55%) had parasagittal meningiomas. Among patients with convexity meningiomas, 75% were female, while among those with parasagittal meningiomas, 65.9% were female. Although the mean age was higher in patients with parasagittal meningiomas than in patients with convexity meningiomas, there was no significant difference between the groups in terms of mean age (P=0.508).

TUMOR HISTOPATHOLOGICAL SUBTYPES:

Examining the histopathological subtypes of all cases revealed that 29 (36.3%) were atypical, 15 (18.8%) were meningothelial, 13 (16.3%) were transitional meningiomas, and 23 (28.8%) were other subtypes. Of all the cases, 43 (53.8%) were grade 1, 28 were grade 2, and 9 (11.3%) were grade 3 meningiomas. When comparing the distribution of histopathological subtypes between the groups, it was found that 33.3% of convexity meningiomas were atypical, 19.4% were meningothelial, 11.1% were transitional; moreover, 36.1% of parasagittal meningiomas were atypical, 20.5% were transitional, 18.2% were meningothelial, and 22.7% were other subtypes.

Results

The mean surgery duration for patients with convexity meningiomas was 207±36.6 min, while that for patients with parasagittal meningiomas was 214±72.6 min. Further, intraoperative craniotomy was enlarged in 6 cases (7.5%), and the development of postoperative EH was observed in 10 cases (12.5%). In addition, 11 patients (13.8%) had previously undergone meningioma surgeries.

When comparing postoperative residual tumors, patients with parasagittal meningiomas had a significantly higher postoperative residual rate (34.1%) than those with convexity meningiomas (5.6%) (P=0.005). Thus, this study revealed a significantly higher recurrence rate in parasagittal meningiomas (13.6%) compared to convexity meningiomas (5.6%) (P=0.033). In the 2-year follow-up, 12 out of 15 patients with residual tumors remained stable. Recurrence was observed in 3 patients with residual tumors and 3 patients without residual tumors during the 3–12-month follow-up period. Radiotherapy was administered to patients who had recurrence. The analysis of demographic and clinical data according to tumor location is presented in Table 1.

Although 15.4% of patients with neuronavigation and 9.3% of patients without neuronavigation had grade 3 tumors, there was no significant correlation between the use of neuronavigation and tumor grades (P=0.676). In addition, even though the incidence of postoperative neurological deficit was lower in patients for whom neuronavigation was used (15.4%) compared to those for whom neuronavigation was not used (22.2%), no significant relationship was found between the groups (P=0.474). No statistically significant difference was found between the groups in the analysis of the effect of neuronavigation use on Simpson grade (P=0.512). Although the percentage of patients (11.5%) with residual tumors in meningioma cases in which neuronavigation was utilized was lower than those in which neuronavigation was not utilized (22.6%), there was no significant difference between the groups (P=0.237). When the effect of neuronavigation use was compared with tumor recurrence, no significant difference was found between the groups in terms of recurrence (P=0.535). Moreover, postoperative development of EH was seen in only 1 patient for whom neuronavigation was utilized, whereas it was seen in 9 patients for whom neuronavigation was not utilized, but the difference was not statistically significant (P=0.104). Further, intraoperative craniotomy enlargement was not performed in any of the patients (n=26) for whom neuronavigation was utilized, while intraoperative craniotomy enlargement was performed in 6 (11.1%) of the patients for whom neuronavigation was not utilized; however, the difference between the groups was not statistically significant (P=0.077). The data of the patients with and without neuronavigation are summarized in Table 2.

This study found that the use of neuronavigation significantly increased the duration of surgery compared to that in cases in which neuronavigation was not used (P=0.023). Specifically, the surgery duration was approximately 30 min longer in the neuronavigation group than in the non-neuronavigation group. The tumor dural surface area/craniotomy area ratio was significantly higher in the meningioma patients in which neuronavigation was used compared to those in which neuronavigation was not utilized (P=0.028). The relationship between surgery duration for patients with and without navigation is presented in Table 3.

When the residual tumor status was compared according to tumor grade, although the residual rate was higher in patients with grade 3 tumors, the difference between groups was not significant (P=0.168). Of the 9 patients with grade 3 meningiomas, 3 (33.3%) had residual tumors. The lowest residual rate was seen in grade 1 meningiomas (11.6%). The relationship between residual tumor and tumor grade is summarized in Table 4.

Although no postoperative sinus injury was observed in any of the parasagittal meningioma patients for whom neuronavigation was used, the difference between neuronavigation use and sinus injury was not significant (P=0.107). Intraoperative superior sagittal sinus injury occurred in 6 (18.7%) of 32 parasagittal meningioma patients without neuronavigation. The relationship between the use of navigation and superior sagittal sinus injury is presented in Table 5. All sinus hemorrhages were stopped by compression with a hemostatic sponge, and bleeding was stopped surgically. None of the patients required sinus repair.

Discussion

Smaller craniotomies were made and complications such as postoperative neurological deficits and epidural hematoma were reduced in patients operated on using the navigation system. It was also found to help remove more tumors and reduce residual and recurrence rates.

Meningiomas are observed approximately twice as frequently in women as in men [7]. In our study, 30% of the patients were male and 70% were female, which is consistent with the literature.

Of all meningiomas, 80.5% were WHO grade 1, 17.7% were grade 2, and 1.7% were grade 3 [10]. Upon analyzing the pathological results of the patients in our study, we found high rates of grade 2 and grade 3 patients (34% and 11%, respectively).

Although the rates of postoperative neurological deficits (eg, loss of motor strength, dysphasia, and aphasia) were lower in patients in whom neuronavigation was utilized compared to those in whom navigation was not utilized, the difference was not statistically significant (P=0.474). Similarly, the neuronavigation group had lower residual and recurrence rates than the non-neuronavigation group, but the difference was not statistically significant (P=0.237 and P=0.535, respectively). The literature reports that neuronavigation can extend tumor resection and reduce recurrence rates [1,4]. Our study found that most residual and recurrent cases were in patients with parasagittal meningiomas, with a statistically significant difference between the groups (P=0.005, P=0.033, respectively). This is due to the superior sagittal sinus invasion in parasagittal meningiomas, which prevents complete tumor excision [11]. Preoperative brain MRI, postoperative cranial CT, and 6-month postoperative control brain MRI from 3 patients are depicted in Figures 1–3.

The patients who underwent surgery with neuronavigation had a significantly longer surgery duration (P=0.023). The use of neuronavigation in cranial surgeries has been reported to shorten the operation time [4,11]. However, it has been observed that the use of neuronavigation in cases of convexity and parasagittal meningiomas, which are superficial tumors, increases the surgery duration. In their study, Akyuz and Kadıoğlu reported that the mean operation time was 40 min longer when neuronavigation was utilized [12]. Additionally, they found that craniotomy dimensions were significantly smaller when neuronavigation was utilized compared to when it was not utilized [4]. In this study, we calculated the ratio of tumor dural surface area to craniotomy area and found that the use of neuronavigation significantly reduced the size of the craniotomy (P=0.028). Although the presence of EH on postoperative CT images was higher in cases without neuronavigation, there was no significant difference between the groups (P=0.104). This may be due to the larger size of the craniotomy in cases without neuronavigation. In our study, intraoperative craniotomy enlargement was performed in 6 cases (11.1%) in which neuronavigation was not utilized. Although there was no significant difference between the groups (P=0.077), the absence of craniotomy enlargement in any of the cases in which neuronavigation was utilized suggests that neuronavigation may be useful in meningioma surgery. Total resection is recommended in meningioma surgery [13]. The craniotomy dimensions and tumor surgery are illustrated in Figures 4 and 5.

Bir et al reported that the use of neuronavigation was decisive in achieving gross total resection in 517 patients with meningioma [4]. Nguyen et al reported that the Simpson I–II resection rate was 82.26% in cases in which neuronavigation was used for falx meningiomas [8]. In our study, Simpson I–II resection was performed in 84.6% of patients who underwent neuronavigation and in 72.2% of patients who did not, but the difference between groups was not statistically significant. We believe that this was due to the superficial localization of the tumors and the fact that most of them were grade 1 tumors. Figure 6 illustrates the use of neuronavigation.

Surgery for meningiomas involves the relatively simple removal of convexity meningiomas. However, parasagittal meningiomas are more difficult to remove completely due to their invasion of the superior sagittal sinus. Complete removal of a tumor may result in complications during and after surgery, such as venous bleeding and sinus thrombosis [3]. Our study found that the residual rate in convexity tumors was significantly lower than that in parasagittal tumors, which is related to sagittal sinus invasion. In addition, intraoperative sagittal sinus injury was observed in 6 patients with parasagittal meningiomas. Neuronavigation was not utilized in any of these cases. The absence of sagittal sinus injury in patients who underwent neuronavigation may be attributed to frequent intraoperative probe checks of vascular structures and tumor borders.

The major limitation of this study is its retrospective design, which caused many biases. The fact that the patients were operated on by different surgeons may also have causes bias. The relatively small number of patients and short follow-up period are other limitations of the present study.

Conclusions

Neuronavigation systems are frequently used in surgeries. With the use of neuronavigation, smaller craniotomies can be performed and total resection of the tumor can be performed more successfully, with better determination of tumor borders during surgery. As a result, postoperative complications, vascular injuries, and blood loss are reduced. Furthermore, intraoperative control increases surgical safety and improves outcomes.