Transcranial-transdural real-time ultrasonography during transsphenoidal resection of a large pituitary tumor. Case report

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.

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.

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.

Intraoperative Identification of a Normal Pituitary Gland and an Adenoma Using Near-Infrared Fluorescence Imaging and Low-Dose Indocyanine Green

BACKGROUND

The intraoperative distinction between normal and abnormal pituitary tissue is crucial during pituitary adenoma surgery to obtain a complete tumor resection while preserving endocrine function. Near-infrared (NIR) fluorescence imaging is a technique to intraoperatively visualize tumors by using indocyanine green (ICG), a contrast agent allowing visualization of differences in tissue vascularization. Although NIR fluorescence imaging has been described in pituitary surgery, it has, in contrast to other surgical areas, never become widely used.

OBJECTIVE

To evaluate NIR fluorescence imaging in pituitary surgery, both qualitatively and quantitatively, and to assess the additional value of resecting adenoma tissue under NIR fluorescence guidance.

METHODS

We included 10 patients planned to undergo transnasal transsphenoidal selective adenomectomy. Patients received multiple intravenous administrations of 5 mg ICG, up to a maximum of 15 mg per patient. Endoscopic NIR fluorescence imaging was performed at multiple points in time. The NIR fluorescent signal in both the adenoma and pituitary gland was obtained, and the fluorescence contrast ratio was assessed.

RESULTS

Four patients had Cushing disease, 1 had acromegaly, and 1 had a prolactinoma. Four patients had a nonfunctioning macroadenoma. In 9 of 10 patients with a histologically proven pituitary adenoma, the normal pituitary gland showed a stronger fluorescent signal than the adenoma. A fluorescence contrast ratio of normal pituitary gland to adenoma of 1.5 ± 0.2 was obtained. In 2 patients; adenoma resection was actually performed under NIR fluorescence guidance instead of under white light.

CONCLUSION

NIR fluorescence imaging can easily and safely be implemented in pituitary surgery. The timing of ICG administration is important for optimal results and warrants further study. It appears that injection of ICG can best be postponed until some part of the normal pituitary gland is identified. Subsequent repeated low-dose ICG administrations improved the distinction between adenoma and gland.

Intraoperative magnetic resonance imaging during surgery for pituitary adenomas: pros and cons

Surgery for pituitary adenomas still remains a mainstay in their treatment, despite all advances in sophisticated medical treatments and radiotherapy. Total tumor excision is often attempted, but there are limitations in the intraoperative assessment of the radicalism of tumor resection by the neurosurgeon. Standard postoperative imaging is usually performed with a few months delay from the surgical intervention. The purpose of this report is to review briefly the facilities and kinds of intraoperative magnetic resonance imaging for all physician and surgeons involved in the management of pituitary adenomas on the basis of current literature. To date, there are several low- and high-field magnetic resonance imaging systems available for intraoperative use and depiction of the extent of tumor removal during surgery. Recovery of vision and the morphological result of surgery can be largely predicted from the intraoperative images. A variety of studies document that depiction of residual tumor allows targeted attack of the remnant and extent the resection. Intraoperative magnetic resonance imaging offers an immediate feedback to the surgeon and is a perfect quality control for pituitary surgery. It is also used as a basis of datasets for intraoperative navigation which is particularly useful in any kind of anatomical variations and repeat operations in which primary surgery has distorted the normal anatomy. However, setting up the technology is expensive and some systems even require extensive remodeling of the operation theatre. Intraoperative imaging prolongs the operation, but may also depict evolving problems, such as hematomas in the tumor cavity. There are several artifacts in intraoperative MR images possible that must be considered. The procedures are not associated with an increased complication rate.

Intraoperative magnetic resonance imaging and early prognosis for vision after transsphenoidal surgery for sellar lesions

Object

Sellar lesions with suprasellar extension may cause loss of visual acuity and visual field damage due to compression of the optic chiasm. Using intraoperative MR (iMR) imaging to detect symptomatic lesion remnants adjacent to the optic chiasm (that may be resected in the same procedure) may positively affect the functional outcome of patients with these lesions. The aim of this study was to evaluate the correlation between visual improvement and optic nerve decompression detected by iMR imaging in patients undergoing transsphenoidal resection of pituitary lesions.

Methods

A total of 32 patients (23 men and 9 women) who underwent transsphenoidal resection of sellar lesions causing visual impairment were included in this study. Tumor volume ranged from 0.9 cm3 to 55.7 cm3 (mean 9.8 ± 11.7 cm3). Preoperative assessment showed visual field damage in 31 patients (97%) and loss of visual acuity in 28 patients (88%). The latency period between the appearance of symptoms and transsphenoidal decompression was 14.9 ± 19.5 weeks.

Results

Intraoperative MR imaging was performed after the resection was believed to be complete, or if further tumor removal was not safely possible due to changed conditions in the surgical field. Complete resection was detected on these initial scans in 17 patients (53%). Partial resection was achieved in 9 patients (28%) and tumor debulking in 6 (19%). Additional resection was possible in 8 (53%) of these 15 patients. Four (50%) of these 8 cases had suprasellar remnants and the optic chiasm was subsequently decompressed. In 5 cases optimal decompression of the optic chiasm was not possible. On early follow-up within 1 month after surgery, overall improvement of visual field damage was observed in 27 patients (87%). In 23 patients (74%), the Goldmann perimetry demonstrated complete recovery. Improvement of visual acuity was noted in 24 patients (86%). Eighteen patients (64%) regained full visual acuity. Identification of a decompressed optic chiasm on iMR imaging was significantly correlated with visual field improvement (p = 0.0007; positive predictive value 0.96, 95% CI 0.81–0.99) and relief of visual acuity deficits (p = 0.0002; positive predictive value 0.96, 95% CI 0.79–0.99). Two patients needed transcranial procedures for symptomatic tumor remnants detected on iMR imaging.

Conclusions

Intraoperative MR imaging findings correlate with prognosis of visual deficits after transsphenoidal decompression of the anterior optic pathways. The use of iMR imaging may prevent revision surgery for unexpected symptomatic remnants.

Imaging of the pituitary: Recent advances

Pituitary lesions, albeit relatively infrequent, can significantly alter the quality of life. This article highlights the role of advanced imaging modalities in evaluating pituitary-hypothalamic axis lesions. Magnetic resonance imaging (MRI) is the examination of choice for evaluating hypothalamic-pituitary-related endocrine diseases. Advanced MR techniques discussed in this article include dynamic contrast-enhanced MRI, 3T MRI, magnetization transfer (MT) imaging, diffusion-weighted imaging (DWI), proton MR spectroscopy, fluorine-18 fluorodeoxyglucose-positron emission tomography, single-photon emission computed tomography, intraoperative MRI, and intraoperative real-time ultrasonography.

Pituitary neurologic surgery: a unique subspecialty in evolution

OBJECTIVE

To review the evolving approaches to surgical management of pituitary tumors during the past century, which may predict future directions.

METHODS

We undertook a retrospective review of selected literature published during the past century and report the trends in the treatment of pituitary tumors.

RESULTS

Harvey Cushing's extraordinary influence on American neurosurgery and remarkably successful pituitary surgical series were the foundation for the development of a highly subspecialized neurosurgical operative field. Continued evolution in the treatment of pituitary tumors has been historically based on the following: (1) the development of exogenous cortisone and vasopressin; (2) the development of high-voltage and nuclear radiation therapy; (3) the experience gained from total hypophysectomy for "endocrine" driven malignant lesions and diabetic retinopathy; (4) the development of the image intensifier and television intraoperative fluoroscopic control; (5) the use of endoscopes in pituitary surgical procedures; (6) the application of the operating microscope to transsphenoidal approaches; (7) the development of the imaging modalities of computed tomographic scanning and subsequent magnetic resonance imaging; and (8) the concepts surrounding "minimally invasive" surgical techniques.

CONCLUSION

The pituitary surgical techniques of today have evolved primarily because of extraordinary past accomplishments. The approaches used continue to maximize tumor resection and preserve functioning pituitary tissue. New intraoperative imaging techniques will forge the future of the field of pituitary neurosurgery, and the expected outcomes will be improved surgical success and lower perioperative morbidity.)

Transcranial echo-guided transsphenoidal surgical approach for the removal of large macroadenomas

Object. Transsphenoidal surgery for the removal of macroadenomas has some disadvantages, including the risk of performing procedures without adequate visualization, difficulties in estimating the amount of residual tumor, and the risk of injuring major vessels. To overcome these disadvantages, the authors have developed transcranial echo-guided transsphenoidal surgery.

Methods. Three patients with large macroadenomas and two patients with irregularly shaped macroadenomas were selected for this operation. In addition to standard preparations for transsphenoidal surgery, in each case the right frontal bone was trephined and an echo probe was inserted transdurally through the trephination hole. During tumor removal, brightness-mode echo images and Doppler color flow images were obtained. The echo images allowed for real-time visualization of the tumor and surrounding brain structures including major arteries and the cisterns; histological heterogeneities of the tumor could also be appreciated. The tumors were removed safely and maximal tumor removal was achieved.

Conclusions. Transcranial echo-guided transsphenoidal surgery provides real-time visualization of tumor removal. The method enhances the safety of this surgery, maximizes the removal of the tumor, and is inexpensive.

Intraoperative magnetic resonance imaging during transsphenoidal surgery

OBJECT

The aim of this study was to evaluate whether intraoperative magnetic resonance (MR) imaging can increase the efficacy of transsphenoidal microsurgery, primarily in non-hormone-secreting intra- and suprasellar pituitary macroadenomas.

METHODS

Intraoperative imaging was performed using a 0.2-tesla MR imager, which was located in a specially designed operating room. The patient was placed supine on the sliding table of the MR imager, with the head placed near the 5-gauss line. A standard flexible coil was placed around the patient's forehead. Microsurgery was performed using MR-compatible instruments. Image acquisition was started after the sliding table had been moved into the center of the magnet. Coronal and sagittal T1-weighted images each required over 8 minutes to acquire, and T2-weighted images were obtained optionally. To assess the reliability of intraoperative evaluation of tumor resection, the intraoperative findings were compared with those on conventional postoperative 1.5-tesla MR images, which were obtained 2 to 3 months after surgery. Among 44 patients with large intra- and suprasellar pituitary adenomas that were mainly hormonally inactive, intraoperative MR imaging allowed an ultra-early evaluation of tumor resection in 73% of cases; such an evaluation is normally only possible 2 to 3 months after surgery. A second intraoperative examination of 24 patients for suspected tumor remnants led to additional resection in 15 patients (34%).

CONCLUSIONS

Intraoperative MR imaging undoubtedly offers the option of a second look within the same surgical procedure, if incomplete tumor resection is suspected. Thus, the rate of procedures during which complete tumor removal is achieved can be improved. Furthermore, additional treatments for those patients in whom tumor removal was incomplete can be planned at an early stage, namely just after surgery.