Endonasal ultrasonography-assisted neuroendoscopic transsphenoidal surgery

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.

Endoscopic ultrasound imaging with high flow mode for endonasal transsphenoidal pituitary surgery

Intraoperative ultrasound during transsphenoidal surgery (TSS) for pituitary tumors has been reported. In reports of endonasal ultrasound (US), Doppler US vessel images were informative and effective in endoscopic TSS. We performed endoscopic US imaging with high flow mode, which is a novel technology, to visualize small vessels during endonasal endoscopic TSS. Six patients (five with pituitary adenomas and one with Rathoke's cleft cyst) underwent endoscopic US-assisted TSS. A small endoscopic US probe (Olympus, BF-UC260FW; diameter, 6.9 mm) was inserted transsphenoidally to the sellar floor and into the sella turcica, and endoscopic US monitoring was performed. By rotating the endoscopic US probe, the internal carotid artery, anterior cerebral artery, middle cerebral artery, various small vessels, optic nerve, and residual tumor were clearly visualized on the endoscopic US images. Real-time animated vessel images around the tumor could be generated when needed during TSS. The tumors were removed without leakage of cerebrospinal fluid in the six patients, and their visual acuity was restored. Endoscopic US with high flow mode can visualize not only main cerebral arteries but also intracranial small vessels on B-mode US images. Pituitary tumors were clearly recognized and removed safely and precisely by monitoring the cerebral artery and its small branches as landmarks.

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.

Trends in endoscopic and microscopic transsphenoidal surgery: a survey of the international society of pituitary surgeons between 2010 and 2020

PURPOSE

This comparative survey of surgical practice patterns between 2010 and 2020 aims to elicit trends in practice patterns for transsphenoidal surgery and to identify areas for improvement.

METHODS

Web-based surveys were sent to the International Society of Pituitary Surgeons via a membership listserv in 2010 and 2020. These 33-item surveys collected information on demographics, surgical approach, perceived advantages and disadvantages, and recommendations for improvements. Statistical analyses were conducted using the Mann-Whitney U test for continuous variables and Fisher's exact test for categorical variables.

RESULTS

There were 51 respondents in 2010 and 82 respondents in 2020. The majority were full-time academic surgeons from the United States or Europe. Preference for a purely endoscopic technique increased from 43% in 2010 to 87% in 2020. Preference for routinely working with an otolaryngologist or second neurosurgeon increased from 35 to 51%. Most surgeons (74%) reported that they were more likely to achieve a greater extent of resection with the endoscope, though 51% noted increased operating time. The most commonly rated advantage (34%) of endoscopic TSS was fewer postoperative nasoseptal perforations; the most commonly (34%) rated disadvantage was more postoperative complications, including cerebrospinal fluid leak. Respondents were divided on whether microscopic TSS should continue to be taught in residency. Many (32%) advocated for improved endoscopic instrumentation and team training.

CONCLUSION

Endoscopic TSS is now the clearly preferred method for surgery amongst a cohort of higher-volume academic neurosurgeons. This trend is likely to continue, and this provides guidelines for future training.

Neurosurgical intraoperative ultrasonography using contrast enhanced superb microvascular imaging -vessel density and appearance time of the contrast agent

Background: Ultrasonography (US) provides real-time information on structures within the skull during neurosurgical operations. Superb microvascular imaging (SMI) is the latest imaging technique for detecting very low-velocity flow with minimal motion artifacts, and we have reported on this technique for intraoperative US monitoring. We combined SMI with administration of contrast agent to obtain detailed information during neurosurgical operations.Materials and methods: Twenty patients diagnosed with brain tumor (10 meningiomas, 5 glioblastomas, 2 hemangioblastomas, 1 schwannoma, 1 malignant lymphoma, 1 brain abscess) underwent neurosurgery under US with SMI and contrast agent techniques. Vessel density and appearance time following contrast administration were analyzed.Results: Flow in numerous vessels was not visualized by SMI alone, but appeared following injection of contrast agent in all cases. Flow in tumors was drastically enhanced by contrast agent in schwannoma, hemangioblastoma and meningioma, compared to normal brain tissue. Flows in the dilated and bent vessels of glioblastoma were also enhanced, although flow in hypoechoic lymphoma remained inconspicuous. The characteristics of tumor vessels were clearly visualized and tumor borders were demonstrated by the difference between tumor flow and brain flow, by the increased tumor vessel density and decreased appearance time of contrast agent compared to normal brain vessels.Conclusions: The combination of SMI and contrast agent techniques for intraoperative US monitoring could provide innovative flow images of tumor and normal brain. The neurosurgeon obtains information about tumor flow and tumor borderline before tumor resection.

Use of intraoperative intracavitary (direct-contact) ultrasound for resection control in transsphenoidal surgery for pituitary tumors: evaluation of a microsurgical series

BACKGROUND

Perisellar infiltration may be responsible for incomplete removal of pituitary tumors. Since intraoperative visualization of parasellar structures is difficult during transsphenoidal surgery, we are describing the use of intraoperative direct contact ultrasound (IOUS).

METHODS

Within 5 years, in 113 transsphenoidal operations (58 male, 55 female, age 14-81 years, 110 pituitary adenomas (mean diameter 26.6 mm, 69 non-secreting adenomas, 41 secreting adenomas), and 1 of each Rathke's cleft cyst, craniopharyngioma, and xanthogranuloma), IOUS was applied. After wide opening of the sellar floor and removal of the intrasellar tumor portions, a commercially available side fire ultrasound probe is introduced, and in direct contact to the sellar envelope, the perisellar space is scanned perpendicular to the axis of the working channel. We compared the results of IOUS to postoperative MRI after 3-6 months.

RESULTS

Identification of the intracavernous ICA, the anterior optic pathway, and the ACA, was possible, it was safe to operate close to them. In 65 operations (58%), further resection of tumor remnants was performed after IOUS. In this selected series, complete resection of tumors (stated by postoperative MRI after 3-6 months) was achieved in 75 operations (66%) and remission was achieved in 18 operations of secreting adenomas (44%). Compared to MRI after 3 to 6 months, the sensitivity of IOUS was 0.568 and the specificity was 0.907. No complications related to IOUS were seen.

CONCLUSIONS

Visualization of the perisellar compartments by IOUS is easy and fast to perform. It allows the surgeon to identify resectable tumor remnants intraoperatively, which otherwise could be missed.

Intraoperative Ultrasound in Patients Undergoing Transsphenoidal Surgery for Pituitary Adenoma: Systematic Review [corrected]

BACKGROUND

Transsphenoidal surgery is the gold standard for pituitary adenoma resection. However, despite advances in microsurgical and endoscopic techniques, some pituitary adenomas can be challenging to cure.

OBJECTIVE

We sought to determine whether, in patients undergoing transsphenoidal surgery for pituitary adenoma, intraoperative ultrasound is a safe and effective technologic adjunct.

METHODS

The PubMed database was searched between January 1996 and January 2016 to identify relevant publications that 1) featured patients undergoing transsphenoidal surgery for pituitary adenoma, 2) used intraoperative ultrasound, and 3) reported on safety or effectiveness. Reference lists were also checked, and expert opinions were sought to identify further publications.

RESULTS

Ultimately, 10 studies were included, comprising 1 cohort study, 7 case series, and 2 case reports. One study reported their prototype probe malfunctioned, leading to false-positive results in 2 cases, and another study' prototype probe was too large to safely enter the sphenoid sinus in 2 cases. Otherwise, no safety issues directly related to use of intraoperative ultrasound were reported. In the only comparative study, remission occurred in 89.7% (61/68) of patients with Cushing disease in whom intraoperative ultrasound was used, compared with 83.8% (57/68) in whom it was not. All studies reported that surgeons anecdotally found intraoperative ultrasound helpful.

CONCLUSIONS

Although there is limited and low-quality evidence available, the use of intraoperative ultrasound appears to be a safe and effective technologic adjunct to transsphenoidal surgery for pituitary adenoma. Advances in ultrasound technology may allow for more widespread use of such devices.

Recent Evolution of Endoscopic Endonasal Surgery for Treatment of Pituitary Adenomas

For the treatment of pituitary tumors, microscopic transsphenoidal surgery has been considered the "gold standard" since the late 1960s. Over the last two decades, however, a worldwide shift towards endoscopic endonasal surgery is in progress for many reasons. These include a wide panoramic view, improved illumination, an ability to look around anatomical corners using angled tip and, in addition, application to the extended approaches for parasellar tumors. Both endoscopic and microscopic approaches appear equally effective for nonfunctioning adenomas without significant suprasellar or lateral extensions, whereas the endoscopic approach may improve outcomes associated with the extent of resection and postoperative complications for larger tumors. Despite many theoretical benefits in the endoscopic surgery, remission rates of functioning adenomas do not substantially differ between the approaches in experienced hands. The endoscopic approach is a valid alternative to the microscopic approach for adenomas. The benefits will be more appreciated in the extended surgery for parasellar tumors.

Applications of Ultrasound in the Resection of Brain Tumors

Neurosurgery makes use of preoperative imaging to visualize pathology, inform surgical planning, and evaluate the safety of selected approaches. The utility of preoperative imaging for neuronavigation, however, is diminished by the well-characterized phenomenon of brain shift, in which the brain deforms intraoperatively as a result of craniotomy, swelling, gravity, tumor resection, cerebrospinal fluid (CSF) drainage, and many other factors. As such, there is a need for updated intraoperative information that accurately reflects intraoperative conditions. Since 1982, intraoperative ultrasound has allowed neurosurgeons to craft and update operative plans without ionizing radiation exposure or major workflow interruption. Continued evolution of ultrasound technology since its introduction has resulted in superior imaging quality, smaller probes, and more seamless integration with neuronavigation systems. Furthermore, the introduction of related imaging modalities, such as 3-dimensional ultrasound, contrast-enhanced ultrasound, high-frequency ultrasound, and ultrasound elastography, has dramatically expanded the options available to the neurosurgeon intraoperatively. In the context of these advances, we review the current state, potential, and challenges of intraoperative ultrasound for brain tumor resection. We begin by evaluating these ultrasound technologies and their relative advantages and disadvantages. We then review three specific applications of these ultrasound technologies to brain tumor resection: (1) intraoperative navigation, (2) assessment of extent of resection, and (3) brain shift monitoring and compensation. We conclude by identifying opportunities for future directions in the development of ultrasound technologies.

Application of endoscopic ultrasonography to intraventricular lesions

BACKGROUND

Anatomical landmarks such as choroid plexus and foramen of Monro are very important to undergo intraventricular surgery safely and effectually. These landmarks would be unclear in cases with a huge cyst or repeat surgery. We report the usability and precautions to apply a bronchoscope with an ultrasonic convex probe to intraventricular surgery.

METHODS

Two patients diagnosed with obstructive hydrocephalus, one with a large cyst and the other with recurrent craniopharyngioma in the third ventricle, were applied to the EBUS system.

RESULTS

In both patients, the EBUS system was applied safely, and lesions beyond the wall of ventricles or the cyst were visible. Color Doppler ultrasonography detected choroid plexus and internal cerebral veins. Furthermore, we performed real-time ultrasound-guided cyst puncture safely on the case with a large cyst. The most important precaution is that the curved portion of the EBUS system is too long to be bent within cerebral ventricles.

CONCLUSIONS

The new EBUS system with an ultrasonic convex probe is a novel and effectual device to perform intraventricular surgery.