Image-guided transsphenoidal surgery for pituitary lesions using Mehrkoordinaten Manipulator (MKM) navigation system

Augmented Reality in Extratemporal Lobe Epilepsy Surgery

Background: Epilepsy surgery for extratemporal lobe epilepsy (ETLE) is challenging, particularly when MRI findings are non-lesional and seizure patterns are complex. Invasive diagnostic techniques are crucial for accurately identifying the epileptogenic zone and its relationship with surrounding functional tissue. Microscope-based augmented reality (AR) support, combined with navigation, may enhance intraoperative orientation, particularly in cases involving subtle or indistinct lesions, thereby improving patient outcomes and safety (e.g., seizure freedom and preservation of neuronal integrity). Therefore, this study was conducted to prove the clinical advantages of microscope-based AR support in ETLE surgery. Methods: We retrospectively analyzed data from ten patients with pharmacoresistant ETLE who underwent invasive diagnostics with depth and/or subdural grid electrodes, followed by resective surgery. AR support was provided via the head-up displays of the operative microscope, with navigation based on automatic intraoperative computed tomography (iCT)-based registration. The surgical plan included the suspected epileptogenic lesion, electrode positions, and relevant surrounding functional structures, all of which were visualized intraoperatively. Results: Six patients reported complete seizure freedom following surgery (ILAE 1), one patient was seizure-free at the 2-year follow-up, and one patient experienced only auras (ILAE 2). Two patients developed transient neurological deficits that resolved shortly after surgery. Conclusions: Microscope-based AR support enhanced intraoperative orientation in all cases, contributing to improved patient outcomes and safety. It was highly valued by experienced surgeons and as a training tool for less experienced practitioners.

Use of Neuronavigation and Augmented Reality in Transsphenoidal Pituitary Adenoma Surgery

The aim of this study was to report on the clinical experience with microscope-based augmented reality (AR) in transsphenoidal surgery compared to the classical microscope-based approach. AR support was established using the head-up displays of the operating microscope, with navigation based on fiducial-/surface- or automatic intraoperative computed tomography (iCT)-based registration. In a consecutive single surgeon series of 165 transsphenoidal procedures, 81 patients underwent surgery without AR support and 84 patients underwent surgery with AR support. AR was integrated straightforwardly within the workflow. ICT-based registration increased AR accuracy significantly (target registration error, TRE, 0.76 ± 0.33 mm) compared to the landmark-based approach (TRE 1.85 ± 1.02 mm). The application of low-dose iCT protocols led to a significant reduction in applied effective dosage being comparable to a single chest radiograph. No major vascular or neurological complications occurred. No difference in surgical time was seen, time to set-up patient registration prolonged intraoperative preparation time on average by twelve minutes (32.33 ± 13.35 vs. 44.13 ± 13.67 min), but seems justifiable by the fact that AR greatly and reliably facilitated surgical orientation and increased surgeon comfort and patient safety, not only in patients who had previous transsphenoidal surgery but also in cases with anatomical variants. Automatic intraoperative imaging-based registration is recommended.

Optimizing MR imaging for intraoperative image guidance in sellar pathologies

PURPOSE

With the advancement of extended endonasal approaches, the ability to surgically reach parasellar tumor extensions increase. The aim of the study was to propose an optimized imaging protocol for surgical guidance in the cavernous sinus (CS) for proper visualization structures at risk.

METHODS

Prospective case control analysis of 20 consecutive pituitary adenoma patients scheduled for endoscopic transnasal surgery. Assessment of the capability of three different MRI sequences (MPRAGE, VIBE, CISS) by 4 investigators to correctly visualize sellar and parasellar structures. Invasiveness and position of the normal pituitary gland were compared with the intraoperative findings.

RESULTS

The consensus between the 4 examiners to achieve the same results for all modalities was 40% for MPRAGE, 70% for VIBE and 60% for CISS sequences (p = 0.155). A consensus of Knosp Grade per patient was 80% for MPRAGE, 100% for VIBE and 90% for CISS (overall kappa 0.60). A higher Knosp Grade was found in MPRAGE sequences compared to the other sequences. Intraoperative status of invasiveness was correctly identified in 12/20 (60%) with MPRAGE, 19/20 (95%) with VIBE and 11/20 (55%) with CISS sequences. The position of the normal pituitary gland was most frequent evaluable in 15/20 (75%) and correctly identified in 12/15 (80%) cases.

CONCLUSION

Our data showed that VIBE sequences obtain the highest degree of consensus with intraoperative findings of invasiveness and position of the normal pituitary gland. VIBE sequences, due to their high spatial resolution and at the same time fast image acquisition could provide improved imaging for neuronavigation.

iMRI During Transsphenoidal Surgery

A variety of intraoperative MRI (iMRI) systems are in use during transsphenoidal surgery (TSS). The variations in iMRI systems include field strengths, magnet configurations, and room configurations. Most studies report that the primary utility of iMRI during TSS lies in detecting resectable tumor residuals following maximal resection with conventional technique. Stereotaxis, neuronavigation, and complication avoidance/detection are enhanced by iMRI use during TSS. The use of iMRI during TSS can lead to increased extent of resection for large tumors. Improved remission rates from hormone-secreting tumors have also been reported with iMRI use. This article discusses the history, indications, and future directions for iMRI during TSS.

An advanced navigation protocol for endoscopic transsphenoidal surgery

OBJECTIVE

To report our clinical experience with an advanced navigation protocol that provides seamless integration into the operating workflow of endoscopic transsphenoidal surgery.

PATIENTS AND METHODS

From 32 consecutive cases of endoscopic transsphenoidal surgery, an optimal setup of continuous electromagnetic instrument navigation was created. Additionally, our standard multimodality image navigation of T1-weighted magnetic resonance (MR) images for soft tissue, MR angiogram for vascular structures, and computed tomography (CT) for solid bone was advanced by the addition of a CT surface rendering for fine paranasal sinus structures. The anatomic structures visualized and their clinical impacts were compared between standard and advanced visualization protocol. Bone-windowed CT images served as reference. The accuracy of the navigation setup was assessed by intraoperative landmark tests. Potential tissue shift was calculated by comparing pre- and postoperative MR angiograms of 20 macroadenomas.

RESULTS

After a learning curve of 2 cases (1 ferromagnetic interference and 1 dislocation of the patient reference tracker), the advanced navigation protocol was feasible in 30 cases. Advanced multimodality imaging was able to visualize significantly finer paranasal sinus structures than multimodality image navigation without CT surface rendering, equal to bone-windowed CT images (P < 0.001, McNemar test). This was found helpful for orientation in cases of complex sphenoid sinus anatomy. The accuracy of the advanced navigation setup corresponded to standard optic navigation with skull fixation. A tissue shift of median 2 mm (range 0-9 mm) was observed in the posterior genu of the internal carotid arteries after tumor resection.

CONCLUSIONS

The advanced navigation protocol permits continuous suction-tracked navigation guidance during endoscopic transsphenoidal surgery and optimal visualization of solid bone, fine paranasal sinus structures, soft-tissue and vascular structures. This may add to the safety of the procedure especially in cases of anatomical variations and in cases of recurrent adenomas with distorted anatomy.

Surgical treatment of pituitary tumours

The surgical treatment of pituitary tumours underwent considerable evolution during the past centennial. Since Schloffer's first description, excellent surgeons refined the surgical techniques, utilised hormonal measurements and imaging investigations at different times to define surgical success or failure. To date, transsphenoidal surgery is the approach of choice for over 90% of pituitary tumours, but still transcranial operations are needed even in experienced hands when asymmetrical and large pituitary tumours with minor intrasellar components present. When the indication for surgery stands, the complication rate to date is relatively low, particularly if the surgeon and his or her centre have sufficient experience in the field. In microadenomas, the success rate reported from expert authors approaches 90%. Generally speaking, patients with non-functioning pituitary adenomas, acromegaly, thyrotropinomas and Cushing's disease are excellent candidates for primary surgical treatment. Re-operations are generally associated with less favourable outcomes. In prolactinomas, the primary therapy is medical; however, when dopamine agonists are not well tolerated or inefficient, an operative treatment should be considered. Although alternative medical treatments exist in acromegaly and thyrotropinomas, surgical treatment is relatively cheap. The implementation of endoscope-assisted, entirely endoscopic, image-guided surgery and intra-operative magnetic resonance (MR) imaging, particularly in combination with utilisation of the established microsurgical techniques, extends the surgical spectrum. Lesions become surgically accessible, which one did not dare to touch even a century ago. Moreover, it seems that the patient's safety has increased and more patients have their tumours completely resected, which is equivalent to a higher remission rate in hormonally active tumours.

TRANSSPHENOIDAL PITUITARY MACROADENOMAS RESECTION GUIDED BY POLESTAR N20 LOW-FIELD INTRAOPERATIVE MAGNETIC RESONANCE IMAGING

OBJECTIVE

To evaluate the applicability of low-field intraoperative magnetic resonance imaging (iMRI) during transsphenoidal surgery of pituitary macroadenomas.

METHODS

Fifty-five transsphenoidal surgeries were performed for macroadenomas (modified Hardy's Grade II–IV) resections. All of the surgical processes were guided by real-time updated contrast T1-weighted coronal and sagittal images, which were acquired with 0.15 Tesla PoleStar N20 iMRI (Medtronic Navigation, Louisville, CO). The definitive benefits as well as major drawbacks of low-field iMRI in transsphenoidal surgery were assessed with respect to intraoperative imaging, tumor resection control, comparison with early postoperative high-field magnetic resonance imaging, and follow-up outcomes.

RESULTS

Intraoperative imaging revealed residual tumor and guided extended tumor resection in 17 of 55 cases. As a result, the percentage of gross total removal of macroadenomas increased from 58.2% to 83.6%. The accuracy of imaging evaluation of low-field iMRI was 81.8%, compared with early postoperative high-field MRI (Correlation coefficient, 0.677; P &lt;0.001). A significantly lower accuracy was identified with low-field iMRI in 6 cases with cavernous sinus invasion (33.3%) in contrast to the 87.8% found with other sites (Fisher's exact test, P &lt;0.001).

CONCLUSION

The PoleStar N20 low-field iMRI navigation system is a promising tool for safe, minimally invasive, endonasal, transsphenoidal pituitary macroadenomas resection. It enables neurosurgeons to control the extent of tumor resection, particularly for suprasellar tumors, ensuring surgical accuracy and safety, and leading to a decreased likelihood of repeat surgeries. However, this technology is still not satisfying in estimating the amount of the parasellar residual tumor invading into cavernous sinus, given the false or uncertain images generated by low-field iMRI in this region, which are difficult to discriminate between tumor remnant and blood within the venous sinus.

Clinical application of a neuronavigation system in transsphenoidal surgery of pituitary macroadenoma

The utility of a neuronavigation system in the transsphenoidal surgery of pituitary macroadenoma was evaluated, and improvement of the surgical outcome is discussed. From 1997 to 2003, a total of 63 patients (male:female=41:22, mean age 58.3 years) with pituitary macroadenoma were treated surgically via transsphenoidal approach using a neuronavigation system in Beijing Tiantan Hospital. Image data for computed tomography or magnetic resonance were obtained and analyzed by the navigation system to make a three-dmensional reconstruction. During the operation, the tumor and its surrounding structures of the sellar region could be located accurately at any time. Among these cases, the tumors were removed totally in 26 cases (41.3%), subtotally in 36 cases (57.1%) and partially in one case (1.6%). Postoperative neurological complications occurred in 15 cases (23.8%). One patient died, the operative mortality was 1.6%. During the operation, the accuracy of the neuronavigation system was 2.3+/-1.1 mm. The neuronavigation system is quite helpful for transsphenoidal surgery of pituitary macroadenoma. Its accuracy of location is very useful and important in determining anatomical structure and protecting normal tissues and vessels. Moreover, fluoroscopy was not required during the surgery.

Treatment of pituitary tumors: surgery

Following a century of technical developments and refinements, a variety of standard operation techniques to date are available for the surgical treatment of pituitary tumors. The vast majority of the lesions can be dealt with satisfactorily utilizing transsphenoidal approaches. The goal of surgical treatment is rapid eradication of the tumor mass, decompression of visual pathways, and elimination of hormonal oversecretion while preserving the normal gland and avoiding potential surgical complications. The tumor's size, extension, and configuration and the magnitude of hormonal oversecretion, are the essential factors that decide whether all the goals can be reached. Another important factor is the individual skill and experience of the surgeon. Still, several lesions that are mainly developed outside of the sella require transcranial approaches, of which the pterional and subfrontal routes are the most widely used. With microsurgical techniques and standard approaches, mortality is far below 1% and morbidity is remarkably low. The most favorable surgical results are obtained with microadenomas, which in the MR image are depicted as distinct low intensity lesions. Only recently has the recovery of pituitary function following surgery been convincingly demonstrated. With the extended transsphenoidal approaches, lesions become accessible that previously have been considered contraindications for transsphenoidal surgery. The introduction of new technical gadgets such as neuronavigation, endoscopy, and intraoperative imaging open new avenues and, even more, widen the spectrum of accessible lesions. Indications for surgery, the preoperative workup, surgical techniques, results, limitations, and new technical developments are briefly reviewed in this article.