Parasellar Anatomy Research Articles

Generating novel pituitary datasets from open-source imaging data and deep volumetric segmentation.

The estimated incidence of pituitary adenomas in the general population is 10-30%, yet radiographic diagnosis remains a challenge. Diagnosis is complicated by the heterogeneity of radiographic features in both normal (e.g. complex anatomy, pregnancy) and pathologic states (e.g. primary endocrinopathy, hypophysitis). Clinical symptoms and laboratory testing are often equivocal, which can result in misdiagnosis or unnecessary specialist referrals. Computer vision models can aid in pituitary adenoma diagnosis; however, a major challenge to model development is the lack of dedicated pituitary imaging datasets. We hypothesized that deep volumetric segmentation models trained to extract the sellar and parasellar region from existing whole-brain MRI scans could be used to generate a novel dataset of pituitary imaging. Six open-source whole-brain MRI datasets, created for research purposes, were included for model development. Deep learning-based volumetric segmentation models were trained using 318 manually annotated MRI scans from a single open-source MRI dataset. Out-of-distribution volumetric segmentation performance was then tested on 418 MRIs from five held-out research datasets. On our annotated images, agreement between manual and model volumetric segmentations was high. Dice scores (a measure of overlap) ranged 0.76-0.82 for both in-distribution and out-of-distribution model testing. In total, 6,755 MRIs from six data sources were included in the final generated pituitary dataset. We present the first and largest dataset of pituitary imaging constructed using existing MRI data and deep volumetric segmentation models trained to identify sellar and parasellar anatomy. The model generalizes well across patient populations and MRI scanner types. We hope our pituitary dataset will be an integral part of future machine learning research on pituitary pathologies.

From Above and Below: The Microsurgical Anatomy of Endoscopic Endonasal and Transcranial Microsurgical Approaches to the Parasellar Region

The parasellar region is one of the most complex of the skull base. In this study, we review the anatomy and approaches to this region through a 360° perspective, correlating microsurgical and endoscopic anatomic nuances of this area. An endoscopic endonasal approach (EEA) and microsurgical dissections were performed. The parasellar anatomy is reviewed and common areas of tumor extensions are assessed. Surgical approaches are discussed based on the anatomic nuances of those regions. The cavernous sinus (CS) can be divided into 2 spaces: posterosuperior, above and behind the internal carotid artery (ICA); and anterior, in front of the cavernous ICA. Those spaces can be approached through the CS walls: anterior and/or medial wall via EEA; or superior and/or lateral wall via transcranial approaches. The relationship of the Meckel cave, adjacent to the lateral and posterior wall of the CS, is relevant for surgical planning. Areas often affected by tumor extension can be divided into 6 regions: superior (cisternal), superolateral (parapeduncular), posterolateral (Meckel cave and petrous bone), medial (sella), anterior (superior orbital fissure), and anterior inferior (pterygopalatine fossa). Anatomic and technical nuances of each of those regions should be taken into consideration when dealing with tumors in the parasellar space. A transcranial approach and EEA provide effective access to the parasellar region. Management of cavernous sinus and Meckel cave tumors requires familiarity with those approaches. Understanding of the surgical anatomy of the parasellar region, from above and below, is therefore necessary for adequate surgical planning and execution.

Extended Endoscopic Endonasal Approach for Craniopharyngioma Removal.

Objective Endoscopic transsphenoidal extended endoscopic approach (EEA) represents a valid alternative to microsurgery for craniopharyngiomas removal, especially for retrochiasmatic lesions without large parasellar extension. The present video illustrates the salient surgical steps of the EEA for craniopahryngioma removal. Patient A 52-year-old man presented with a bitemporal hemianopia and a bilateral decreased visual acuity. MRI showed a Kassam type III cystic craniopharyngioma with a solid component ( Fig. 1 , panels A and B). Surgical Procedure The head is rotated 10 degrees toward the surgeons. The nasal step is started through the left nostril with a middle turbinectomy. A nasoseptal flap is harvested and positioned in the left choana. The binostril approach allows a large sphenoidotomy to expose the key anatomic landmarks. The craniotomy boundaries are the planum sphenoidale superiorly, the median opticocarotid recesses, the internal carotid artery laterally and the clival recess inferiorly. After dural opening and superior intercavernous sinus coagulation, the tumor is entirely removed ( Fig. 2 , panels A and B). Skull base reconstruction is ensured by fascia lata grafting and nasoseptal flap positioning. Results Postoperative MRI showed the complete tumor resection ( Fig. 1 , panels C and D). At 3 months postoperatively, the bitemporal hemianopia regressed and the visual acuity improved. A novel left homonymous hemianopia developed secondary to optic tract manipulation. Conclusions The extended EEA is a valid surgical approach for craniopharyngioma resection. A comprehensive knowledge of the sellar and parasellar anatomy is mandatory for safe tumor removal with decreased morbidity and satisfactory oncologic results. The link to the video can be found at: https://youtu.be/NrCPPnVK2qA .

A morphometric survey of the parasellar region in more than 2700 skulls: emphasis on the middle clinoid process variants and implications in endoscopic and microsurgical approaches.

OBJECTIVE The middle clinoid process (MCP) is a bony projection that extends from the sphenoid bone near the lateral margin of the sella turcica. The varied prevalence and morphological features of the MCP in populations stratified by age, race, and sex are unknown; however, the knowledge of its anatomy and preoperative recognition on CT scans can aid greatly in complication avoidance and management. The aim of this study was to further illustrate the surgical anatomy of the parasellar region and to quantify the incidence of MCP and caroticoclinoid rings (CCRs) in dried preserved human anatomical specimens. METHODS The presence, dimensions, morphological classification (incomplete, contact, and CCR), and intracranial relations of the MCP were measured in 2726 dried skull specimens at the Hamann-Todd Osteological Collection at the Cleveland Museum of Natural History. Specific morphometric data points were recorded from each of these hemiskulls, and categorized based on age, sex, and ethnicity. Linear and logistic regressions were used to determine associations between explanatory variables and MCP morphology. Computed tomography scans of the skull specimens were obtained to explore radiological landmarks for different types of MCPs. Illustrative intraoperative videos were also analyzed in the light of these crucial surgical landmarks. RESULTS The sample included 2250 specimens from males and 476 from females. Specimens were classified as either "white" (60.5%) or "black" (39.2%). An MCP was found in 42% of specimens, with 60% of those specimens presenting bilaterally. Fully ossified CCR comprised 27% of all MCPs, and contact (defined as contact without ossification between MCP and anterior clinoid process) comprised 4% of all MCPs. White race (relative to black race) and increasing age were significant predictors of MCP presence (p < 0.001). White race was significantly associated with greater average MCP height (p < 0.001). Among skulls with CCR, both male sex and older age (> 70 years relative to < 50 years) were associated with increased CCR diameter (p < 0.001). No other significant predictors or associations were observed. The CT scans of skulls replicated and validated the authors' morphometric observations on incomplete, contact, and CCR patterns adequately. The surgical strategies of clinoid bone removal are validated, with appropriate video illustrations. CONCLUSIONS Variations in the patterns of bony MCPs can pose a significant risk for injury to the internal carotid artery during parasellar procedures, especially those involving clinoidectomy and optic strut drilling. Understanding parasellar anatomy, especially on skull-base CT imaging, may be integral to surgical planning and preoperative risk counseling in both transcranial and extended endonasal procedures, as well as to preparing for complications management perioperatively.

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

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. To study and analyze the anatomic variations of the MCP in the general population using computed tomography scans. 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. 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 ± 1.4mm, the average sagittal base diameter was 5.0 ± 1.8mm, the average length was 4.7 ± 1.7mm, the average midline distance was 5.9 ± 2.3mm, the average distance from the sellar-clival junction was 10.6 ± 3.3mm, 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. 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.

Endoscopic Orientation of the Parasellar Region in Sphenoid Sinus with Ill-Defined Bony Landmarks: An Anatomic Study

The sphenoid bony landmarks are important for endoscopic orientation in skull base surgery but show a wide range of variations. We aimed to describe an instructional model for the endoscopic parasellar anatomy in sphenoid sinuses with ill-defined bony landmarks. Five preserved injected cadaveric heads and four sides of dry skulls were studied endoscopically via transethmoid, transsphenoidal approach. The parasellar region was exposed by drilling along the maxillary nerve (V2) canal [the length of the foramen rotundum (FR) between the middle cranial fossa and the pterygopalatine fossa]. This was achieved by drilling in the inferior part of the lateral wall of posterior ethmoids immediately above the sphenopalatine foramen. Cavernous V2 was traced to the paraclival internal carotid artery (ICA). Cavernous sinus (CS) apex was exposed by drilling a triangle bounded by V2 and its canal inferiorly, bone between FR and superior orbital fissure (SOF) anteriorly, and ophthalmic nerve (V1) superiorly. Drilling was continued toward the annulus of Zinn (AZ) and optic nerve superiorly and over the intracavernous ICA posteriorly. Endoscopic measurements between V2, SOF, AZ, and opticocarotid recess were obtained. Endoscopic systematic orientation of parasellar anatomy is presented that can be helpful for approaching sphenoid sinus with ill-defined bony landmarks.

Endoscopic Transsphenoidal Pituitary Surgery with Intraoperative Magnetic Resonance Imaging

The two most recent significant advances in pituitary surgery have been the endonasal endoscopic approach and intraoperative magnetic resonance imaging (IMRI). Each provides improved visualization of intra- and parasellar anatomy with the goal of attaining a complete resection. The combination of the two techniques has not been previously reported in the literature. We performed endoscopic, endonasal resection of pituitary macroadenomas in 15 patients using the Polestar N-10 (0.12T) IMRI (Odin Medical Technologies, Inc., Newton, MA). Eleven patients had nonfunctioning tumors, three had acromegaly, and one had a medication-resistant prolactinoma. The effect of the magnetic field on the cathode ray tube screen and the image quality of the IMRI images were assessed. The presence of residual tumor on IMRI was noted and then re-examined with the endoscope. Although the Polestar N-10 is a low Tesla magnet, the IMRI caused significant distortion of the cathode ray tube screen regardless of the viewing angle. This was overcome with the use of a wall-mounted plasma screen. IMRI images were obtained in all cases and were of sufficiently high quality to demonstrate adequate decompression of the optic chiasm and the removal of all suprasellar tumor. In three cases, residual tumor was found with IMRI that was resected endoscopically before the completion of surgery. In four other cases, potential residual tumor was examined endoscopically and found to be normal postoperative change. In eight cases no residual intrasellar tumor was seen on the IMRI. Preresection visual deficits improved in all cases and the insulin-like growth factor levels normalized in two of three cases. There were no delayed cerebrospinal fluid leaks. Combining intraoperative endoscopy and IMRI is feasible and distortion of the cathode ray tube screen can be overcome with the use of either a plasma or liquid crystal display screen. Each technology provides complementary information, which can assist the surgeon in safely maximizing the extent of resection. In this small series using a low-field magnet, rates of residual tumor following endoscopic transsphenoidal surgery were less than have been reported following microscope-based transsphenoidal surgery.

Parasellar lesions

The sellar and parasellar region is an anatomically complex area that represents a crucial crossroad of important adjacent structures, e.g. orbits, cavernous sinus and its content, polygon of Willis, hypothalamus through the pituitary stalk and dural reflections forming the diaphragm sellae and the walls of the cavernous sinuses. Although the cavernous sinus represents the most relevant parasellar structure, from the practical and clinical point of view all the structures that surround the sella turcica can be included in the parasellar region. CT and, mainly, MRI are the imaging modalities to study and characterise the normal anatomy and the majority of processes in this region. We present a practical short review of the most relevant CT and MRI characteristics, such as location, nature of contrast enhancement and presence of cystic components, together with clinical findings, which permit differentiation of the most frequent and less common lesions found in the parasellar region. -A short review of the anatomy and clinical symptoms related to the parasellar region. -Radiological characterisation, mainly by MRI, of the many lesions that alter the structure and function of sellar and parasellar anatomy. -Description of the MRI features that permit differentiation among less common lesions.

Transsphenoidal approaches to anterior skull base lesions

The transphenoidal approach to intracranial lesions is most commonly used for pituitary tumors. It can also be used to biopsy or treat midline skull base lesions from the planum sphenoidale to the clivus. Proper application of this approach requires an understanding of sellar and parasellar anatomy. In this article, we describe our techniques, discuss modifications introduced by others, and review the advantages and pitfalls of transsphenoidal microsurgery. This approach is best suited to extradural lesions that extend no further than 1.5 cm from midline. The most common complications are cerebrospinal fluid leak and endocrinopathy.

The parasellar region of human infants: cavernous sinus topography and surgical approaches.

In this study the authors analyze the peculiarities of the parasellar anatomy and the topography of surgical approaches to the parasellar region (PSR) in human infants. Forty-nine specimens of the PSR obtained at autopsy were studied using microdissection and histological analysis. Important distances between anatomical landmarks were measured with the aid of a dissecting microscope. One serially sectioned specimen was three-dimensionally reconstructed and analyzed on the computer screen by using the authors' new episcopic reconstruction technique. The anatomy of the infant PSR differs distinctly from that of the adult. The parasellar portion of the internal carotid artery (ICA) does not form a siphon, but takes a straight course, and the venous pathways as well as the cranial and sympathetic nerves have different topographical relationships. Analyses of surgical approaches demonstrate that, in young children, the anterolateral approach can be used to reach the pterygopalatine compartment, the superior ophthalmic vein, and those pathological processes that extend from the orbit into the PSR. The approach via Parkinson's triangle can be used in 45% of cases to access the pathological processes that occur in the voluminous space above and behind the posterior flexure of the parasellar ICA. Taking this route, sympathetic nerve fibers passing through the PSR are not at risk, but some arterial branches that run within the lateral wall of the sinus can complicate this approach. This study presents a guideline that can assist radiologists and neurosurgeons in the planning and performance of interventions within the PSR of neonates and young children.

IMAGING OF SELLAR AND PARASELLAR PATHOLOGY

This article reviews the complex anatomic relationships between structures in the sellar and parasellar regions. Normal anatomy and the normal imaging spectrum are reviewed, with emphasis on the diversity of pathology that originates from this region. Both CT and MR imaging may be used to evaluate the sellar and parasellar regions. This article discusses how modern imaging techniques enable characterization of the many lesions that alter the structure and function of normal sellar and parasellar anatomy.

The parasellar region of human infants: cavernous sinus topography and surgical approaches

Object In this study the authors analyze the peculiarities of the parasellar anatomy and the topography of surgical approaches to the parasellar region (PSR) in human infants. Methods Forty-nine specimens of the PSR obtained at autopsy were studied using microdissection and histological analysis. Important distances between anatomical landmarks were measured with the aid of a dissecting microscope. One serially sectioned specimen was three-dimensionally reconstructed and analyzed on the computer screen by using the authors' new episcopic reconstruction technique. The anatomy of the infant PSR differs distinctly from that of the adult. The parasellar portion of the internal carotid artery (ICA) does not form a siphon, but takes a straight course, and the venous pathways as well as the cranial and sympathetic nerves have different topographical relationships. Analyses of surgical approaches demonstrate that, in young children, the anterolateral approach can be used to reach the pterygopalatine compartment, the superior ophthalmic vein, and those pathological processes that extend from the orbit into the PSR. The approach via Parkinson's triangle can be used in 45% of cases to access the pathological processes that occur in the voluminous space above and behind the posterior flexure of the parasellar ICA. Taking this route, sympathetic nerve fibers passing through the PSR are not at risk, but some arterial branches that run within the lateral wall of the sinus can complicate this approach. Conclusions This study presents a guideline that can assist radiologists and neurosurgeons in the planning and performance of interventions within the PSR of neonates and young children.

Magnetic Resonance Imaging of Pituitary Adenomas

Seven pituitary adenomas with suprasellar extensions were examined with a 0.5 tesla superconductive magnetic resonance imaging (MRI) system. MRI clearly displayed the anatomical structures, such as an optic pathway and internal carotid arteries in the cavernous sinus, but it could not show the cavernous sinus itself or the nerves in it. Sagittal and coronal inversion recovery images were very useful for visualization of the optic pathway and short spin echo images of the parasellar anatomy. To delineate tumors, coronal and sagittal images were superior to axial images in all pulse sequences. Prolongation of the spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) was observed in every case with no relation to tissue type of the tumors.