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

Sella turcica bridging: a systematic review

PURPOSE

Sella turcica bridging (STB) has significant implications during neurosurgery, since it alters regional anatomy; however, no studies have investigated the global prevalence of STB. Our systematic review aimed to establish the global prevalence of STB, in specimens/individuals with and without comorbidities, in males and females, and of partial, complete, unilateral, and bilateral bridging.

METHODS

A literature search was conducted in MEDLINE/PubMed, ScienceDirect, and Google Scholar with various key words relating to Sella turcica bridging. Quantitative data were extracted and statistically analysed.

RESULTS

Eighty-two studies satisfied our inclusion criteria. The mean prevalence of STB was 26.54%, and most prevalent in Europe. STB was detected more frequently using radiological investigations. STB was less prevalent in healthy individuals (21.12%) when compared to individuals with comorbidities (33.31%). Partial STB was found to be the more prevalent in both individuals with (41.06%) and without (21.55%) comorbidities. The prevalence of unilateral and bilateral STB was only studied in healthy individuals, with unilateral bridging being the more prevalent (6.26% vs 3.84%).

CONCLUSION

The global overall prevalence of Sella turcica bridging in the general population was found to be higher than previously thought. Anatomical and embryological textbooks should consider including information on STB in their texts, due to its considerable prevalence and effects to the regional anatomy.

Sellar Remodeling after Surgery for Nonfunctioning Pituitary Adenoma: Intercarotid Distance as a Predictor of Recurrence

Introduction  As they grow, pituitary adenoma can remodel the sella turcica and alter anatomical relationships with adjacent structures. The intercarotid distance (ICD) at the level of the sella is a measure of sella width. The purpose of this study was to (1) assess how ICD changes after transsphenoidal surgery and (2) explore whether the extent of ICD change is associated with tumor recurrence. Methods  A retrospective analysis of preoperative and postoperative coronal magnetic resonance imaging (MRI) scans was carried out by two independent assessors on patients who underwent transsphenoidal surgery for nonfunctioning pituitary macroadenomas. Preoperative tumor volume and any change in ICD following surgery were recorded and compared between groups. Logistic regression models of recurrence were generated. Results  In 36 of 42 patients, ICD fell after surgery (mean = 1.8 mm) and six cases were static. At time of follow-up (mean = 77 months), 25 had not required further intervention and 17 had undergone second surgery or radiosurgery. In patients in whom no further intervention has yet been necessary, the postoperative reduction in ICD was significantly smaller than in those who required repeat intervention (1.1 vs. 2.7 mm respectively, p  < 0.01). ICD decrease was weakly correlated with tumor volume ( r  = 0.35). ICD decrease was a significant predictor of recurrence (odds ratio [OR] = 3.15; 95% confidence interval [CI]: 1.44-6.87), largely independent of tumor volume. Conclusion  For most patients, ICD falls following surgical excision of a nonfunctioning pituitary macroadenoma. A greater reduction in ICD postsurgery appears to predict recurrence. Change in ICD shows promise as a radiographic tool for prognosticating clinical course after surgery.

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

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.