Abstract

Background: The endonasal transsphenoidal approach is a fundamental technique for the resection of pituitary tumors. Anatomical variability of the sphenoid sinus and its relationship with neurovascular structures can influence surgical planning and outcomes.

Methods: A retrospective observational prevalence study was conducted using data from 102 patients from the INVIMEDIC database. Preoperative tomographic images in DICOM format were analyzed using RadiAnt Viewer^®. Data were collected in Microsoft Excel and analyzed with the Statistical Package for the Social Sciences 28 for Windows, including cross tables, Pearson’s Chi-square test, and logistic regression analysis.

Results: Significant sex-based differences were identified in sphenoid sinus morphology. The mean anteroposterior length in the overall population was 24.55 mm, with males showing greater depth (26.01 mm vs. 22.98 mm in females) and width (33.26 mm vs. 29.94 mm in females).

Conclusion: Significant morphological differences in the sphenoid sinus were observed between sexes, highlighting dimensions that contrast with previous studies. These findings emphasize the importance of assessing anatomical variations to optimize transsphenoidal approach planning and minimize surgical risks.

Keywords: Anatomy, Endonasal, Neuronavigation, Pituitary, Sellar, Transsphenoidal

INTRODUCTION

The endonasal transsphenoidal approach has gained prominence in neurosurgery and otorhinolaryngology as a minimally invasive technique for accessing the sellar region to resect pituitary tumors.[ 10 ] First described by Schloffer in 1907, its widespread adoption began in 1967 when Hardy introduced the surgical microscope.[ 3 ] Despite its advantages, this approach presents challenges due to significant anatomical variations among patients.

Preoperative computed tomography (CT) imaging and neuronavigation, introduced in 2008, have become essential tools for identifying these variations and optimizing surgical planning.[ 11 ] This approach is currently the gold standard for treating pituitary tumors, which account for 17% of all intracranial tumors,[ 8 , 9 ] with pituitary adenomas comprising 90% of cases.[ 6 ]

While epidemiological data in Latin America remain scarce,[ 2 ] a study in Cuenca, Ecuador (2012–2016) found that 65% of pituitary adenomas were microadenomas, with prolactinomas being the most prevalent among young and middle-aged adults.[ 4 ] At Hospital Luis Vernaza in Guayaquil, 149 surgeries using this approach were performed between 2015 and 2023.[ 7 ]

Previous studies have extensively analyzed anatomical variations affecting this surgical corridor. In 2021, Monash University in Melbourne conducted a systematic review of skeletal, vascular, and neural variations in the nasal, sphenoidal, and sellar regions.[ 3 ] Similar studies have been conducted in the Netherlands (2010)[ 12 ] and Turkey (2009) using patient imaging and cadaveric specimens, respectively.[ 1 , 12 ] However, no comparable research has been performed in Latin America.

Understanding the detailed anatomy of the endonasal transsphenoidal corridor is crucial for successful surgery. Beyond classical anatomical knowledge, identifying patient-specific anatomical variants enhances preoperative planning, improves surgical accuracy, optimizes resource utilization, and ultimately reduces perioperative complications and morbidity.[ 5 ]

MATERIALS AND METHODS

Study design

This is a retrospective observational analytical study based on previously acquired data, with no intervention by the researchers. The study aims to analyze the prevalence of anatomical variants observed in preoperative CT scans for surgical planning in patients undergoing an endonasal transsphenoidal surgical corridor approach to the sella turcica.

Study population

The study includes all available patients who underwent surgery using the endonasal transsphenoidal corridor approach between 2021 and 2023, as recorded in the INVIMEDIC database. INVIMEDIC, a commercial provider of neuronavigation services, supplied CT images from multiple healthcare centers in Ecuador:

Hospital Luis Vernaza – Junta de Beneficencia de Guayaquil (Guayaquil)

Inclusion criteria

Patients who underwent surgery using the endonasal transsphenoidal corridor approach to access the sella turcica.

Exclusion criteria

Patients who underwent surgery using alternative surgical corridors to access the sella turcica.

Sample size calculation

The study included all available cases (n = 102 patients), eliminating the need for sample size estimation.

Methodology

This was a non-experimental, cross-sectional analytical cohort study of male and female patients aged 25–74 years. The study utilized preoperative CT scans in DICOM format, provided by INVIMEDIC. Image analysis was performed using RadiAnt DICOM Viewer^®. Data were tabulated in Microsoft Excel.

Each CT scan was analyzed individually by the principal investigator in collaboration with the Neurosurgery Department at Hospital Luis Vernaza, ensuring technical accuracy in identifying and categorizing anatomical variants.

Anatomical reference points and measurements

Quantitative anatomical measurements were performed using standardized radiological protocols.

Anteroposterior length of the sphenoid sinus

Measured from the medial ostium to the posterior wall of the sphenoid sinus

Lateral width of the sphenoid sinus

Measured between the lateral walls at the widest point of the sphenoid sinus

Height of the sphenoid sinus

Measured between the highest point of the sinus roof and the lowest point of the sinus floor

Intercarotid distance

Measured between the right and left carotid foramina

RESULTS

A total of 102 patients were analyzed after applying inclusion and exclusion criteria. Statistical analyses were performed using the Statistical Package for the Social Sciences 28, and the following key findings were obtained:

Sphenoid sinus dimensions and intercarotid distance

These findings are summarized in Table 1 . The general distribution of anteroposterior length is illustrated in Figure 1 . The distribution of sinus height is shown in Figure 2 .

Table 1:

Sphenoid sinus dimensions and intercarotid distance by sex.

Figure 1:

Simple boxplot of the anteroposterior length of the sphenoid sinus (mm) in all patients.

Figure 2:

Simple boxplot of the height of the sphenoid sinus (mm) in all patients.

Males exhibited significantly larger sphenoid sinuses in all dimensions compared to females.

Figure 3:

Simple boxplot of the lateral length of the sphenoid sinus (mm) in all patients.

Prevalence of anatomical variants

The detailed prevalence data are presented in Table 2 .

Table 2:

Prevalence of anatomical variants in the nasal and sphenoid regions by sex.

Nasal deviated septum: Present in 71.1% of males versus 28.9% of females (P < 0.001)

Regression analysis

Regression results for Onodi cells and pneumatization are shown in Table 3 .

Table 3:

Significant regression analysis results for Onodi cells and clinoid pneumatization as predictors.

The presence of Onodi cells and clinoid pneumatization was significantly associated with altered sphenoid sinus dimensions (P = 0.011 and P = 0.045, respectively)

DISCUSSION

This study provides valuable insights into anatomical variations in the endonasal transsphenoidal surgical corridor and their relationship with sex and other variables. By analyzing preoperative CT scans, we identified key anatomical differences relevant to surgical planning.

Sphenoid sinus morphology and surgical implications

Sex-based differences were observed in sphenoid sinus dimensions, with males exhibiting larger anteroposterior and lateral lengths. Notably, the mean anteroposterior length was 24.55 mm, significantly exceeding the 17 mm described by Rhoton.[ 10 ] This finding suggests that longer nasal speculums and extended endoscopic or microsurgical instruments may be required for surgical access in this population.

Nasal variants and surgical approach

Nasal septum deviation was significantly more common in males (71.1% vs. 28.9%, P < 0.001), indicating a higher likelihood of septal deviation in male patients, which may influence the choice of nostril for the surgical approach.

Intercarotid distance and surgical safety

The mean intercarotid distance was 19.85 mm, 3.3 mm above the upper limit of the theoretical range (13.6– 16.5 mm).[ 10 ] Figure 4 shows the distribution of intercarotid distance in the studied population. A wider intercarotid space facilitates surgical maneuverability, potentially reducing the risk of intraoperative vascular injury and hemorrhagic complications.

Figure 4:

Simple boxplot of the intercarotid distance (mm) in all patients.

Sphenoid septations and surgical navigation

A positive correlation was observed between sphenoid sinus width and the number of septations, indicating that larger sinuses tend to have more septations. This anatomical complexity may increase the risk of misidentification of key landmarks, reinforcing the importance of intraoperative neuronavigation for accurate anatomical orientation.

Regression analysis and predictive models

While certain variables, such as Onodi cells and clinoid pneumatization, demonstrated significant associations with anatomical dimensions, others did not reach statistical significance. Sex-based distribution and correlation of these dimensions are shown in Figure 5 . This highlights the need to better refine predictive models to assess anatomical variations in different patient populations better. Representative preoperative CT images showing these measurements are presented in Figure 6 .

Figure 5:

Scatter plot of the anteroposterior length and lateral length of the sphenoid sinus (mm) by sex of the patients.

Figure 6:

Computed tomography scan images showing measurements of the dimensions of the sphenoid sinus.

CONCLUSION

This study provides a detailed understanding of anatomical variations in the endonasal transsphenoidal corridor and their relationship with key patient characteristics. Significant sex-based differences were identified, emphasizing the need to consider patient sex in surgical planning and instrument selection.

Males exhibited deeper and wider sphenoid sinuses, which may require longer surgical instruments for adequate access. In addition, the prevalence of anatomical anomalies such as nasal septum deviation, bony spurs, and concha bullosa varied by sex, impacting intraoperative decision-making.

A correlation was observed between sphenoid sinus width and the number of septations, which may complicate anatomical orientation and reinforce the importance of neuronavigation. While age appeared to influence sphenoid sinus height, the variability in data suggests that age alone is not a reliable predictor of anatomical dimensions. Logistic regression analysis highlighted associations between certain anatomical features and sphenoid sinus dimensions, though further validation is required to strengthen predictive models.

These findings enhance our understanding of anatomical variability in the transsphenoidal corridor, offering valuable insights for preoperative assessment and surgical strategy. However, further validation studies are necessary to confirm these findings and optimize their clinical applicability.

Ethical approval:

The Institutional Review Board approval is not required, as it is retrospective analysis of anonymized preoperative CT scans without patient identifiers .The project was officially approved under reference code CM-CT-196-2023, dated August 31, 2023.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Abuzayed B, Tanriöver N, Ozlen F, Gazioğlu N, Ulu MO, Kafadar AM. Endoscopic endonasal transsphenoidal approach to the sellar region: Results of endoscopic dissection on 30 cadavers. Turk Neurosurg. 2009. 19: 237-44

2. Aponte AA, Vargas EA, Salazar LR. Epidemiology of pituitary adenomas: An overview of latin america and the world. Neurociencias J. 2021. 28: 45-68

3. Castle-Kirszbaum M, Uren B, Goldschlager T. Anatomic variation for the endoscopic endonasal transsphenoidal approach. World Neurosurg. 2021. 156: 111-9

4. García Iñiguez JD, Barahona Ulloa WF, editors. Características de adenomas hipofisarios en el hospital josé carrasco arteaga. Cuenca 2012-2016. Mexico: UCUENCA; 2018. p.

5. Korkmaz M, Yildirim AE, Osun A, Alagoz F, Divanlioglu D, Daglioglu E. Endoscopic endonasal transsphenoidal pituitary surgery: Experience of 80 cases. Turk Neurosurg. 2015. 25: 883-7

6. Manejo de Los Tumores de Hipófisis. Available: https://www.elsevier.es/es/revista/revista/medica/clinica/las/condes/202/pdf/S0716864017300664 [Last accessed on 2023 28].

7. Martínez Neira DG, editors. Final report of activities as Head of the Neurosurgery Service at Hospital Luis Vernaza. [Original in Spanish]. Guayaquil: Junta de Beneficencia de Guayaquil; 2023. p. 2-28

8. Pituitary gland tumor - statistics cancer net. Available from: https://www.cancer.net/cancer-types/pituitary-gland-tumor/statistics [Last accessed on 2023 Aug 28].

9. Recovery outlook for pituitary tumor. Expert surgeon. Available from: https://www.aaroncohen/gadol.com/en/patients/pituitary/tumor/survival/recovery/outlook [Last accessed on 2023 Aug 28].

10. Rhoton AL, Rhoton AL, editors. Cranial anatomy and surgical approaches. Rhoton’s cranial anatomy and surgical approaches. Chapter Sellar Region. New York: Thieme; 2003. p. 441-72

11. Rodríguez Rosales KP, Peñalver Paolini CL, Benítez Vázquez AM, Rossi Prieto MI, Herraiz Hidalgo L, Martínez de Vega Fernández V, editors. Anatomical variants in the planning of endoscopic endonasal transsphenoidal surgery. [Educational exhibit, original in Spanish]. Madrid, Spain: Quirón Salud; 2022. p. 1-14

12. Van Lindert EJ, Ingels K, Mylanus E, Grotenhuis JA. Variations of endonasal anatomy: Relevance for the endoscopic endonasal transsphenoidal approach. Acta Neurochir (Wien). 2010. 152: 1015-20