Utility of intraoperative ultrasonography for resection of pituitary adenomas: a comparative retrospective study

Intraoperative Ultrasonography in Pituitary Surgery Revisited: An Institutional Experience and Systematic Review on Applications and Considerations

OBJECTIVE

The primary objective of this systematic review is to evaluate the effectiveness of intraoperative ultrasound (IOUS) in improving outcomes in patients undergoing pituitary surgery.

METHODS

A systematic review was performed by searching MEDLINE (PubMed), Web of Science, Scopus, and Embase electronic bibliographic databases from conception to 2022.

RESULTS

The included studies yielded a total of 660 patients, with 488 patients undergoing IOUS. Outcome were available for 341 patients treated with IOUS and 157 patients who were treated without the IOUS application, and the remission rates following surgery were 76% and 59%, respectively. Only 2 studies reported remission rates for both groups, and meta-analysis for these studies showed significant superiority of intraoperative ultrasonography (Random effect, odds ratio 4.99, P < 0.01). Regarding extent of resection, IOUS resulted in 71% gross total resection, while absence of IOUS yielded a gross total resection rate of 44%. Among studies with available follow-up on IOUS, the recurrence rate was 3%. Pituitary dysfunction (34%), cerebrospinal fluid leak (31%), and central nervous system infection (8%) were the most common complications in the IOUS group. The mean follow-up was 19.97 months in studies reporting follow-up time.

CONCLUSIONS

The application of the IOUS is both safe and effective and could improve the outcome of pituitary surgeries. IOUS can assist surgeons in the identification of pituitary tumors and their surrounding anatomy and can help minimize the risk of complications associated with this complex surgical procedure.

Side-Firing Intraoperative Ultrasonograhy for Resection of Giant Pituitary Adenomas

BACKGROUND

Suprasellar extension, cavernous sinus invasion, and involvement of intracranial vascular structures and cranial nerves are among the challenges faced by surgeons operating on giant pituitary macroadenomas. Intraoperative tissue shifts may render neuronavigation techniques inaccurate. Intraoperative magnetic resonance imaging can solve this problem, but it may be costly and time consuming. However, intraoperative ultrasonography (IOUS) allows for quick, real-time feedback and may be particularly useful when facing giant invasive adenomas. Here, we present the first study examining technique for IOUS-guided resection specifically focusing on giant pituitary adenomas.

OBJECTIVE

To describe the use of a side-firing ultrasound probe in the resection of giant pituitary macroadenomas.

METHODS

We describe an operative technique using a side-firing ultrasound probe (Fujifilm/Hitachi) to identify the diaphragma sellae, confirm optic chiasm decompression, identify vascular structures related to tumor invasion, and maximize extent of resection in giant pituitary macroadenomas.

RESULTS

Side-firing IOUS allows for identification of the diaphragma sellae to help prevent intraoperative cerebrospinal fluid leak and maximize extent of resection. Side-firing IOUS also aids in confirmation of decompression of the optic chiasm via identification of a patent chiasmatic cistern. Furthermore, direct identification of the cavernous and supraclinoid internal carotid arteries and arterial branches is achieved when resecting tumors with significant parasellar and suprasellar extension.

CONCLUSIONS

We describe an operative technique in which side-firing IOUS may assist in maximizing extent of resection and protecting vital structures during surgery for giant pituitary adenomas. Use of this technology may be particularly valuable in settings in which intraoperative magnetic resonance imaging is not available.

Automatic rigid image Fusion of preoperative MR and intraoperative US acquired after craniotomy

BACKGROUND

Neuronavigation of preoperative MRI is limited by several errors. Intraoperative ultrasound (iUS) with navigated probes that provide automatic superposition of pre-operative MRI and iUS and three-dimensional iUS reconstruction may overcome some of these limitations. Aim of the present study is to verify the accuracy of an automatic MRI - iUS fusion algorithm to improve MR-based neuronavigation accuracy.

METHODS

An algorithm using Linear Correlation of Linear Combination (LC2)-based similarity metric has been retrospectively evaluated for twelve datasets acquired in patients with brain tumor. A series of landmarks were defined both in MRI and iUS scans. The Target Registration Error (TRE) was determined for each pair of landmarks before and after the automatic Rigid Image Fusion (RIF). The algorithm has been tested on two conditions of the initial image alignment: registration-based fusion (RBF), as given by the navigated ultrasound probe, and different simulated course alignments during convergence test.

RESULTS

Except for one case RIF was successfully applied in all patients considering the RBF as initial alignment. Here, mean TRE after RBF was significantly reduced from 4.03 (± 1.40) mm to (2.08 ± 0.96 mm) (p = 0.002), after RIF. For convergence test, the mean TRE value after initial perturbations was 8.82 (± 0.23) mm which has been reduced to a mean TRE of 2.64 (± 1.20) mm after RIF (p < 0.001).

CONCLUSIONS

The integration of an automatic image fusion method for co-registration of pre-operative MRI and iUS data may improve the accuracy in MR-based neuronavigation.

Case report: Side-firing intraoperative ultrasound guided endoscopic endonasal resection of a clival chordoma

Clival chordomas are locally invasive midline skull base tumors arising from remnants of the primitive notochord. Intracranial vasculature and cranial nerve involvement of tumors in the paraclival region necessitates image guidance that provides accurate real-time feedback during resection. Several intraoperative image guidance modalities have been introduced as adjuncts to endoscopic endonasal surgery, including stereotactic neuronavigation, intraoperative ultrasound, intraoperative MRI, and intraoperative CT. Gross total resection of chordomas is associated with a lower recurrence rate; therefore, intraoperative imaging may improve long-term outcomes by enhancing the extent of resection. However, among these options, effectiveness and accessibility vary between institutions. We previously published the first use of an end-firing probe in the resection of a clival chordoma. End-firing probes provide a single field of view, primarily limited to depth estimation. In this case report, we discuss the benefits of employing a novel minimally invasive side-firing ultrasound probe as a cost-effective and time-efficient option to navigate the anatomy of the paraclival region and guide endoscopic endonasal resection of a large complex clival chordoma.

Side-firing intraoperative ultrasound applied to resection of pituitary macroadenomas and giant adenomas: A single-center retrospective case-control study

Introduction

Multiple intraoperative navigation and imaging modalities are currently available as an adjunct to endoscopic transsphenoidal resection of pituitary adenomas, including intraoperative CT and MRI, fluorescence guidance, and neuronavigation. However, these imaging techniques have several limitations, including intraoperative tissue shift, lack of availability in some centers, and the increased cost and time associated with their use. The side-firing intraoperative ultrasound (IOUS) probe is a relatively new technology in endoscopic endonasal surgery that may help overcome these obstacles.

Methods

A retrospective analysis was performed on patients admitted for resection of pituitary adenomas by a single surgeon at the University of Mississippi Medical Center. The control (non-ultrasound) group consisted of twelve (n=12) patients who received surgery without IOUS guidance, and the IOUS group was composed of fifteen (n=15) patients who underwent IOUS-guided surgery. Outcome measures used to assess the side-firing IOUS were the extent of tumor resection, postoperative complications, length of hospital stay (LOS) in days, operative time, and self-reported surgeon confidence in estimating the extent of resection intraoperatively.

Results

Preoperative data analysis showed no significant differences in patient demographics or presenting symptoms between the two groups. Postoperative data revealed no significant difference in the rate of gross total resection between the groups (p = 0.716). Compared to the non-US group, surgeon confidence was significantly higher (p &lt; 0.001), and operative time was significantly lower for the US group in univariate analysis (p = 0.011). Multivariate analysis accounting for tumor size, surgeon confidence, and operative time confirmed these findings. Interestingly, we noted a trend for a lower incidence of postoperative diabetes insipidus in the US group, although this did not quite reach our threshold for statistical significance.

Conclusion

Incorporating IOUS as an aid for endonasal resection of pituitary adenomas provides real-time image guidance that increases surgeon confidence in intraoperative assessment of the extent of resection and decreases operative time without posing additional risk to the patient. Additionally, we identified a trend for reduced diabetes insipidus with IOUS.

The Current State of Visualization Techniques in Endoscopic Skull Base Surgery

Skull base surgery has undergone significant progress following key technological developments. From early candle-lit devices to the modern endoscope, refinements in visualization techniques have made endoscopic skull base surgery (ESBS) a standard practice for treating a variety of conditions. The endoscope has also been integrated with other technologies to enhance visualization, including fluorescence agents, intraoperative neuronavigation with augmented reality, and the exoscope. Endoscopic approaches have allowed neurosurgeons to reevaluate skull base neuroanatomy from new perspectives. These advances now serve as the foundation for future developments in ESBS. In this narrative review, we discuss the history and development of ESBS, current visualization techniques, and future innovations.

Detection of a pituitary macroadenoma with transcranial ultrasonography: Principles and potential clinical applications

Transcranial color-coded duplex sonography (TCCS) allows to study intracranial vessels through the intact skull, but the visualization of normal and pathologic brain structures in adults is often suboptimal due to inadequate acoustic window. The full potential of TCCS for clinical practice remains unfulfilled. Here, we describe the ability of TCCS to detect a non-functioning pituitary macroadenoma in a 58-year-old man affected by headache. The macroadenoma was visualized as a roundish, well-defined mass, mildly hyperechogenic compared to the hypoechogenic mesencephalic brainstem but mainly hypoechogenic compared to the surrounding intracranial structures. Intracranial vessels represented useful landmarks. Using tissue harmonic imaging mode, the borders of the macroadenoma were visualized more clearly. Macroadenoma characteristics were confirmed by magnetic resonance imaging. Neurosonologists should be aware of the possibility to incidentally find, during routinary TCCS, pituitary macroadenomas or other brain tumors (as incidentalomas), worthy to be recognized and referred for further investigations.

A Novel Intraoperative Ultrasound Probe for Transsphenoidal Surgery: First-in-human study

Background. Ultrasound has been explored as an alternative, less bulky, less time-consuming and less expensive means of intraoperative imaging in pituitary surgery. However, its use has been limited by the size of its probes relative to the transsphenoidal corridor. We developed a novel prototype that is more slender than previously reported forward-viewing probes and, in this report, we assess its feasibility and safety in an initial patient cohort. Method. The probe was integrated into the transsphenoidal approach in patients with pituitary adenoma, following a single-centre prospective proof of concept study design, as defined by the Innovation, Development, Exploration, Assessment and Long-Term Study (IDEAL) guidelines for assessing innovation in surgery (IDEAL stage 1 - Idea phase). Results. The probe was employed in 5 cases, and its ability to be used alongside the standard surgical equipment was demonstrated in each case. No adverse events were encountered. The average surgical time was 20 minutes longer than that of 30 contemporaneous cases operated without intraoperative ultrasound. Conclusion. We demonstrate the safety and feasibility of our novel ultrasound probe during transsphenoidal procedures to the pituitary fossa, and, as a next step, plan to integrate the device into a surgical navigation system (IDEAL Stage 2a - Development phase).

Current Limitations of Intraoperative Ultrasound in Brain Tumor Surgery

While benefits of intraoperative ultrasound (IOUS) have been frequently described, data on IOUS limitations are relatively sparse. Suboptimal ultrasound imaging of some pathologies, various types of ultrasound artifacts, challenging patient positioning during some IOUS-guided surgeries, and absence of an optimal IOUS probe depicting the entire sellar region during transsphenoidal pituitary surgery are some of the most important pitfalls. This review aims to summarize prominent limitations of current IOUS systems, and to present possibilities to reduce them by using ultrasound technology suitable for a specific procedure and by proper scanning techniques. In addition, future trends of IOUS imaging optimization are described in this article.