The implications of microsurgical anatomy for surgical approaches to the sellar region

Endoscopic Orientation of Juxta-pituitary Carotid in Transsphenoidal Approaches: Critical Considerations for Clinical Applications

Introduction  In sphenoid sinuses with ill-defined carotid bony landmarks, accidental injury of the internal carotid artery (ICA) remains one of the most challenging complications, which is particularly reported in the endoscopic endonasal transsphenoidal approaches (EETAs). Objectives  To describe an anatomical model for the endoscopic orientation of the juxta-pituitary segment of the ICA in relation to the lateral opticocarotid recess (OCR) as a nearby bony landmark. Methods  Dissection was performed progressively, simulating the EETA, in twenty fresh adult cadavers. After reducing the posterior and lateral walls of the sphenoid sinuses, various measurements were taken from both lateral OCRs to "contact points" on the juxta-pituitary segment of the ICA and lateral margins of the pituitary gland. Results  The current results have enabled us to divide the region between the lateral OCRs into 3 compartments: 2 lateral parasellar compartments contain juxta-pituitary segments of the ICA with a mean width of 8 mm and a narrow range from 7 mm to 10 mm; and a central intercarotid sellar compartment represents the safe region for bone drilling, showing widely variable widths ranging from 9 mm to 20mm. In all specimens, the variation in the width of the intercarotid compartment correlated with the distance between both lateral OCRs. Conclusion  The present study improves surgeon awareness of the variations in the course of the ICA through the EETA along sphenoid sinuses with ill-defined bony landmarks. An appreciation of the measurements taken in the present study can help in operative training, and can also provide a base for future studies to confirm ICA courses associated with a higher risk of injury.

Endoscopic Orientation of Juxta-Pituitary Carotid in Transsphenoidal Approaches: Critical Considerations for Clinical Applications

Accidental injury of the internal carotid artery (ICA) remains one of the most challenging complications reported in the endoscopic endonasal transsphenoidal approaches (EETA) particularly, in sphenoid sinuses with ill-defined carotid bony landmarks. The purpose of this study was to describe an anatomical model for the endoscopic orientation of juxta-pituitary segment of ICA in relation to the lateral optico-carotid recess (OCR) as a nearby bony landmark. Cadaveric dissection was conducted progressively in twenty fresh adult cadavers simulating the EETA. After reducing posterior and lateral walls of sphenoid sinuses, various measurements were taken from both lateral OCRs to "contact points" of the juxta-pituitary segment of ICA and lateral margins of the pituitary gland. Current results have enabled us to divide the region between lateral OCRs into three compartments. Two lateral parasellar compartments contain juxta-pituitary segments of ICA showing a mean width of 8 mm; with a narrow range of 7-10 mm; and a central inter-carotid sellar compartment represents the safe region for bone drilling showing widely variable widths ranging between 9 to 20 mm. In all specimens; variation in the width of the inter-carotid compartment correlated with the distance between both lateral OCRs. This study improves surgeons' awareness of the ICA course variations in the EETA through sphenoid sinuses with ill-defined bony landmarks. An appreciation of the measurements gathered from this study can help in operative training, and can also provide a base for future studies to confirm ICA courses associated with higher risk of injury.

Microanatomic Study of the Optic Canal

BACKGROUND

The continuous development of microsurgical techniques to treat lesions in and around the optic canal (OC) emphasizes the need for an accurate understanding of the microanatomy of the region.

METHODS

Forty anatomic specimens were studied, with emphasis on the OC. The sphenoid bone and related structures were decalcified, added to animal gelatin, cut into 1-mm thick slices, and observed through a surgical microscope. The OC was considered the course that contained exclusively the optic nerve (ON) and ophthalmic artery.

RESULTS

The mean distance between the medial walls of the OC was 12.2 mm, and the OC had an average length of 12.06 mm. The OC has a horizontal oval shape in the proximal (internal) segment; a round shape in the middle segment; and a vertical oval shape in the distal (external) segment at the orbital cavity. In the middle segment of the OC, the thickest wall of the OC was the lateral (average: 0.68 mm), while the medial, inferior, and superior wall measures had averages of 0.75, 0.40, and 0.39 mm, respectively. The lateral wall of the sphenoid sinus is located under the OC, and the inferior wall of the OC separates both structures. The ophthalmic artery inside the OC was always located under the ON, between the dural sheaths, and had an average diameter of 1.03 mm.

CONCLUSIONS

The neurovascular structures within the OC vary in size and shape. The anatomic knowledge of the OC and its variations allows better surgical results and minimizes the surgical morbidity.

Anatomic and histologic features of diaphragma sellae that effects the suprasellar extension

This study aimed to determine the anatomical and histological features of diaphragma sellae that affect the suprasellar extension of intrasellar tumours. Twenty-four fresh adult cadavers were dissected for the study. Diaphragma sellae and pituitary capsules with sellar structures were resected. The diaphragma sellae was anatomically reviewed in detail. Immunohistochemical staining was performed for collagen types I, II, III, and IV. We examined the suprasellar growth of 13 sellar tumours extending superiorly through the diaphragma sellae by performing a series of 2704 endoscopic transnasal operations to analyse the anatomic and histologic results of the study. The diameter of the foramen of diaphragma sellae varied between specimens. Of 24 specimens, the diaphragma sellae in five (21%) had a tight-type foramen and those in 19 (79%) were more spacious. An increased expression of collagen types I and IV was observed in the pituitary capsule and the diaphragma sellae. In this clinical series, we observed that all types of sellar tumours could expand through the foramen. We observed radiologically and intraoperatively that the diaphragma sellae was displaced laterally and formed a dome in two cases with an adenoma extending to the suprasellar area. Two types of suprasellar extension through the diaphragma sellae are possible: 1) The collagen structure of diaphragma sellae can be destroyed by invasive tumours; 2) The morphology of the foramen of the diaphragma sellae facilitates suprasellar tumoural extension. All sellar tumours, including non-invasive cystic tumours, may invade the suprasellar area by expanding through the foramen of the diaphragma sellae.

Microsurgical treatment of craniopharyngioma: Experiences on 183 consecutive patients

This study aimed to summarize the clinical experiences and postoperative effects of microsurgical approaches for craniopharyngioma.A total of 183 craniopharyngioma patients who underwent microsurgical treatment since March 2009 to March 2015 in our hospital were included in current research. Surgical approaches were selected based on preoperative evaluations, including tumor locations, sizes, and growth patterns. Active measurements to manage water-electrolyte disorder and insipidus were taken for postoperative treatments. During the follow-up, patients were monitored for residual or recurrent tumor by postoperative contrast MRI scans done 1 to 3 months after surgery.The used surgical approaches were as follows: frontopterional approach (76 cases), anterior interhemispheric approach (58 cases), transcallosal approach (10 cases), transsphenoidal approach (15 cases), unilateral subfrontal approach (15 cases), and combined approaches (9 cases). Around 124 cases (72.7%) received total tumor resection, 37 patients (20.2%) underwent subtotal resection, and 13 patients (7.1%) underwent partial removal. No significant difference was found on the postoperative complications among the different microsurgical approaches (all, P > .05). A total of 111 cases had an intact pituitary stalk preservation and 26 cases had partially preserved stalks during surgery. Visual improvement was achieved in 54 patients and visual deterioration occurred in 22 cases. Postoperative insipidus appeared in 114 cases and water-electrolyte disorder occurred in 99 cases. The postsurgical follow-up ranged from 3 to 69 months with a mean duration of 27.3 months and 23 patients suffered recurrence.Based on careful preoperative evaluation, microsurgical treatments may be safe and effective approach to improve postoperative outcomes of craniopharyngioma patients.

Gross total resection of pituitary adenomas after endoscopic vs. microscopic transsphenoidal surgery: a meta-analysis

BACKGROUND

Microscopic transsphenoidal surgery (mTSS) is a well-established method to address adenomas of the pituitary gland. Endoscopic transsphenoidal surgery (eTSS) has become a viable alternative, however. Advocates suggest that the greater illumination, panoramic visualization, and angled endoscopic views afforded by eTSS may allow for higher rates of gross total tumor resection (GTR). The aim of this meta-analysis was to determine the rate of GTR using mTSS and eTSS.

METHODS

A meta-analysis of the literature was conducted using PubMed, EMBASE, and Cochrane databases through July 2017 in accordance with PRISMA guidelines.

RESULTS

Seventy case series that reported GTR rate in 8257 pituitary adenoma patients were identified. For all pituitary adenomas, eTSS (GTR=74.0%; I² = 92.1%) was associated with higher GTR as compared to mTSS (GTR=66.4%; I² = 84.0%) in a fixed-effect model (P-interaction < 0.01). For functioning pituitary adenomas (FPAs) (n = 1170 patients), there was no significant difference in GTR rate between eTSS (GTR=75.8%; I² = 63.9%) and mTSS (GTR=75.5%; I² = 79.0%); (P-interaction = 0.92). For nonfunctioning pituitary adenomas (NFPAs) (n = 2655 patients), eTSS (GTR=71.0%; I² = 86.4%) was associated with higher GTR as compared to mTSS (GTR=60.7%; I² = 87.5%) in a fixed-effect model (P-interaction < 0.01). None of the associations were significant in a random-effect model (all P-interaction > 0.05). No significant publication bias was identified for any of the outcomes.

CONCLUSION

Among patients who were not randomly allocated to either approach, eTSS resulted in a higher rate of GTR as compared to mTSS for all patients and for NFPA patients alone, but only in a fixed-effect model. For FPA, however, eTSS did not seem to offer a significantly higher rate of GTR. These conclusions should be interpreted with caution because of the nature of the included non-comparative studies.

Anatomy of the posterior and middle ethmoidal arteries via computed tomography

OBJECTIVE

The aim of this study is to investigate the anatomy of the posterior and middle ethmoidal arteries from the viewpoint of an endoscopic sinus surgeon.

METHODS

Based on 100 computed tomography images, the anatomical position of the posterior ethmoidal artery in relation to the posterior ethmoid cells was classified into five types. The presence of the posterior and middle ethmoidal arteries, their distance from the skull base, and their length exposed in the ethmoid cells were measured. The association of patients' age and sex, presence of the middle ethmoidal artery, and anatomical type of the posterior ethmoidal artery with the posterior ethmoidal artery distance from the ethmoid roof was analyzed.

RESULTS

The posterior ethmoidal artery's position, relative to the ethmoid cell walls, was most often near the first wall, anterior to the optic canal (92.5%). The posterior ethmoidal artery's distance from the skull base ranged from 0 to 6.4 mm (mean: 1.2 mm). Older age, longer length of the posterior ethmoidal artery exposed in the ethmoid cells, and absence of the middle ethmoidal artery were positively associated with a longer posterior ethmoidal artery distance from the skull base.

CONCLUSION

Attention should be paid to the posterior and middle ethmoidal arteries.

Photoacoustic-based approach to surgical guidance performed with and without a da Vinci robot

Death and paralysis are significant risks of modern surgeries, caused by injury to blood vessels and nerves hidden by bone and other tissue. We propose an approach to surgical guidance that relies on photoacoustic (PA) imaging to determine the separation between these critical anatomical features and to assess the extent of safety zones during surgical procedures. Images were acquired as an optical fiber was swept across vessel-mimicking targets, in the absence and presence of teleoperation with a research da Vinci Surgical System. Vessel separation distances were measured directly from PA images. Vessel positions were additionally recorded based on the fiber position (calculated from the da Vinci robot kinematics) that corresponded to an observed PA signal, and these recordings were used to indirectly measure vessel separation distances. Amplitude- and coherence-based beamforming were used to estimate vessel separations, resulting in 0.52- to 0.56-mm mean absolute errors, 0.66- to 0.71-mm root-mean-square errors, and 65% to 68% more accuracy compared to fiber position measurements obtained through the da Vinci robot kinematics. Similar accuracy was achieved in the presence of up to 4.5-mm-thick ex vivo tissue. Results indicate that PA image-based measurements of the separation among anatomical landmarks could be a viable method for real-time path planning in multiple interventional PA applications.

Differentiation between Posterior Sinuses Using the Medial Orbital Floor as a Landmark

Objectives This study aims to evaluate the difference in height between the floors of the posterior ethmoid and sphenoid sinuses with respect to the medial orbital floor (MOF) to confirm this difference as a landmark for identification of the posterior sinuses. It also aims to describe this difference regarding the type of pneumatization of the sphenoid sinus (conchal, presellar, and sellar). Design A cross-sectional study was conducted. Study Center The study was conducted at the Department of Radiology of Hospital de Clínicas de Porto Alegre, a tertiary care university hospital in Southern Brazil. Materials and Methods A standardized and computerized analysis of 100 tomography scans of sinuses (200 sides), in patients older than 18 years, was carried out. Results Mean vertical distance (height) from the MOF to the floor of the posterior ethmoid and sphenoid sinuses was 0.72 ± 1.85 mm and 9.48 ± 3.81 mm, respectively. There was no statistically significant difference as compared with sex and side. We found conchal-type sphenoid sinus pneumatization in 1.5% (n = 3), presellar in 13.5% (n = 27), and sellar in 85% (n = 170), whereas the vertical distance between the MOF and the floor of the sphenoid sinus was 2.04 ± 0.81 in the conchal-type sinuses, 5.71 ± 2.49 in the presellar sinuses, and 10.21 ± 3.52 in the sellar sinuses. No sphenoid sinus showed its floor above the MOF, regardless of the type of pneumatization. Discussion and Conclusion The present study demonstrates that there is a difference between the floor of the posterior sphenoid and ethmoid sinuses in adults, which is more evident when the sphenoid sinus is well pneumatized. These data suggest that the difference in height between the floors of the sinus investigated in our study may be considered during endoscopic sinus surgery to guide adequate localization, but the surgeon should be aware of the type of pneumatization of the sphenoid sinus to use this landmark.

Morphometric Analysis of the Middle Clinoid Process Using Maxillofacial Computed Tomography Scans

BACKGROUND

The interest in detailed anatomy of the sella and parasellar regions has resurged recently due to the wide clinical applications of the expanded endoscopic approaches to the skull base. The middle clinoid process (MCP) is a bony structure that can affect wide endoscopic exposure of the sella and parasellar region.

OBJECTIVE

To study and analyze the anatomic variations of the MCP in the general population using computed tomography scans.

METHODS

A total of 150 maxillofacial computed tomography scans were reviewed to characterize the MCP. Only adult patients without intracranial or nasal pathology were included. Measurements were made in the axial and sagittal planes to determine the maximum diameter, length, angulation, and location of the MCP.

RESULTS

The prevalence of the MCP was 30.7% in male and 42.7% in female patients. Of the MCPs, 41.8% were ring forming, whereas 76.4% were pneumatized. Quantitatively, the average axial base diameter was 4.6 ± 1.4 mm, the average sagittal base diameter was 5.0 ± 1.8 mm, the average length was 4.7 ± 1.7 mm, the average midline distance was 5.9 ± 2.3 mm, the average distance from the sellar-clival junction was 10.6 ± 3.3 mm, the average sagittal angle was 91.0 ± 21.1°, and the average axial angle was 45.2 ± 15.5°. A significant increase was found in the prevalence of MCPs in white patients compared with black patients, and a significantly greater midline distance and axial angle were found in male compared with female patients.

CONCLUSION

A clear understanding of the sellar and parasellar anatomy is crucial for successful and safe expanded endoscopic approaches. This study provides a quantitative anatomic characterization of the MCP in the U.S. population with demographic data analysis.

Localization of Transcranial Targets for Photoacoustic-Guided Endonasal Surgeries

Neurosurgeries to remove pituitary tumors using the endonasal, transsphenoidal approach often incur the risk of patient death caused by injury to the carotid arteries hidden by surrounding sphenoid bone. To avoid this risk, we propose intraoperative photoacoustic vessel visualization with an optical fiber attached to the surgical tool and an external ultrasound transducer placed on the temple. Vessel detection accuracy is limited by acoustic propagation properties, which were investigated with k-Wave simulations. In a two-layer model of temporal bone (3200 m/s sound speed, 1-4 mm thickness) and surrounding tissues, the localization error was ≤2 mm in the tranducer's axial dimension, while temporal bone curvature further degraded target localization. Phantom experiments revealed that multiple image targets (e.g. sphenoid bone and vessels) can be visualized, particularly with coherence-based beamforming, to determine tool-to-vessel proximity despite expected localization errors. In addition, the potential flexibility of the fiber position relative to the transducer and vessel was elucidated.

The transition from microscopic to endoscopic transsphenoidal surgery: the experience at Brigham and Women's Hospital

OBJECTIVE

As interest and enthusiasm for the use of the endoscope in transsphenoidal anterior skull base and pituitary surgery increases, neurosurgeons are increasingly adopting endoscopic technology and associated novel concepts. Often this involves a transition from the standard operating microscope as the main means of visualization to the operating endoscope (2D or 3D) during surgery.

METHODS

The authors' experience with this transition is described, including the rationale, advantages and disadvantages of the two surgical techniques.

RESULTS

The successful use of endoscopic surgery for a large variety of pathological problems involving the anterior skull base and the pituitary region is presented. Perceived advantages for the patient and the surgeon are described, as is the occasional need for transition back to the microscopic approach.

CONCLUSIONS

The endoscopic approach and its allied technology are here to stay. They are useful and occasionally preferable methods for treating a variety of suitable lesions involving the anterior skull base. The importance of incorporating the basic principles of skull base surgery is emphasized.

Anatomical analysis on the lateral bone window of the sella turcica: a study on 530 adult dry skull base specimens

OBJECTIVE

To investigate the morphometric characteristics of the lateral bone window (LBW) of the sella turica.

METHODS

A descriptive anatomical study of LBW was performed in 530 cases of dry skull base specimens with relatively complete sella turcica. Detailed morphometric characteristics such as dimensions and classification of the LBW was studied. All data analysis was performed using SPSS 17.0 statistical software.

RESULTS

LBW is located in the lateral bony structures of sella turcica. The mean area sizes of the LBW were 75.99 ± 25.81 mm(2) (left) and 76.00 ± 25.53 mm(2) (right). There was no significant difference and there was a ​​good positive correlation between bilateral areas of the LBWs. The area size of the LBWs is graded as follows: Grade A (< 60 mm(2)), B (60~90 mm(2)) and C (> 90 mm(2)). LBW morphology was typed as follows: Type I, II, III, IV. And Tpye III includes Type IIIa and IIIb; Type IV includes Type IVa, IVb, IVc, IVd.

CONCLUSIONS

The lateral bone window of sella turcica is an important structure located between pituiary fossa and parasellar region. The morphological measurements and variations of LBW in this study will provide preliminary data for further anatomical study of sella turcica. Moreover, knowing detailed anatomy of this region is essential for neurosurgeons who make surgery on cranial base or for teaching about the sella turcica in the neuroanatomy lab.

Observation of the neurohypophysis, pituitary stalk, and adenohypophysis during endoscopic pituitary surgery: demonstrative findings as clues to pituitary-conserving surgery

BACKGROUND

High-definition imaging in endoscopic transsphenoidal pituitary surgery accounts for significantly better identification of anatomic structures. This report presents the clinical images of the adenohypophysis and neurohypophysis under high-definition endoscopic observation, and provides some clues for pituitary-sparing surgery.

METHODS

Ten demonstrative cases of pituitary lesions, including three cases of gonadotropin-producing pituitary adenoma, two cases of somatotropin-secreting pituitary adenoma, and five cases of Rathke's cleft cysts, were entered in this study. From these cases, we extracted helpful intraoperative findings that affected the surgeon's decision about surgical procedures and led to favorable results.

RESULTS

The extracted findings contain the following lessons: (1) to find a boundary plane that separate a lesion from the pituitary; (2) to mark the difference of color between the adenohypophysis and the neurohypophysis; (3) to identify the location of the pituitary stalk connecting to the neurohypophysis; (4) to observe the color change of the pituitary induced by decompression; (5) to know pathological findings of the pituitary surface; (6) to distinguish the parenchyma of the neurohypophysis from pathological tissues; and (7) to recognize the intrasellar findings at the completion of removal. Recognition of these findings led to an excellent result in each case.

CONCLUSIONS

Despite being shown in a limited number of cases, on the basis of HD endoscopic images, accurate identification of the neurohypophysis and the pituitary stalk as well as adenohypophysis during surgery contributes to pituitary-conserving operations.

Diaphragma sellae: a surgical reference for transsphenoidal resection of pituitary macroadenomas

OBJECTIVE

To classify patterns of descent of the diaphragma sellae (DS) to the sella turcica after transsphenoidal resection of pituitary macroadenomas and to determine whether there is any correlation between type of descent and volume or growth pattern of the tumor, as well as the presence of any postoperative hormone alteration, cerebrospinal fluid leak, and/or residual tumor.

METHODS

One hundred patients with pituitary macroadenomas in which microsurgical transsphenoidal approach was indicated were prospectively included. We classified patterns of descent of the DS into four types: type A: symmetrical descent with a central fold corresponding to the pituitary stalk; type B: asymmetrical with a lateralized fold; type C: symmetrical and uniform descent without any fold; and type D: minimal or no descent in absence of visible residual tumor. A correlation was made between these types of descent and clinical and radiological findings.

RESULTS

The largest tumors were types A and B; endocrine deficit was more frequent in types A and C, whereas the possibility of residual tumor was more elevated in types B and D. No statistically significant differences were found regarding tumor morphology and cerebrospinal fluid leakage.

CONCLUSIONS

Our results suggest that pattern of descent of the DS may serve as a reference to determine the risk of leaving residual tumor as well as the possibility of developing postoperative endocrine deficit. It is apparent that tumor volume, more than morphology, is the main factor determining type of descent of the DS.