The relationship between sphenoidal sinus and sella turcica morphometry in the Turkish population: a retrospective study.

PURPOSE: The anatomical position of the sphenoidal sinus (SS) is very important for neurosurgeons because of the transsphenoidal approach to the pituitary gland. Therefore, the aim of this study was to determine the volume and shape of the SS and its relationship with the morphometry of the sella turcica. METHODS: This study included CT images of 282 males and 258 females with a mean age of 50.52 years (range 18-75) who underwent head CT. The morphometric values of the sella turcica and the volume of the SS were measured on the included radiologic images. Measurements were made on the sagittal slice closest to the midline in T1 sequence. Morphometric measurements were made with Micro Dicom Viewers software program and volume measurements were made with ITK SNAP software program. RESULTS: In this study, 4 types of SS shapes were obtained in the whole population: amorphous, pentagonal, triangular and quadrilateral. The mean SS volume was 7055.88 mm3 in males and 5694.48 mm3 in females and a statistically significant difference was observed (p < 0.001). In addition, a statistically significant difference was found between the sexes in the width and surface area parameters of the sella turcica (p < 0.05). CONCLUSION: In this study, the morphometric relationship between the shape of the sinus sphenoidale and sella turcica was demonstrated between men and women. In particular, the shape of the sinus sphenoidale was found to be anthropometrically different between men and women in the Turkish population. It is hypothesised that the data obtained in our study will guide surgeons performing transsphenoidal approach.

Morphological and Metrical Relationships Between Sphenoid Sinus and Sella Turcica: Possible Applications in Transnasal Transsphenoidal Surgery.

INTRODUCTION: Transsphenoidal surgeries imply the risk of intraoperative lesions to the neurovascular structures surrounding the sphenoid sinus (SS). Aim of the present study is to assess the metrical and morphologic relationships existing between SS and sella turcica (ST). MATERIALS AND METHODS: Two hundred computed tomography-scans of patients were selected. For each patient volumes of SS were calculated from their 3-dimensional models segmented through ITK-SNAP program. Variants of SS in pneumatisation and sellar diameters [antero-posterior (AP) diameter, depth, and length] were evaluated on each computed tomography-scan. Correlations among different measurements were assessed through Spearman test ( P <0.01), whereas associations between sellar parameters and presence of pneumatisation variants were assessed through Mann-Whitney test ( P <0.01). RESULTS: In males, pneumatization of the greater wings was related to smaller AP diameter ( P <0.01) and depth of ST ( P <0.01), whereas in females lower values of depth were found in patients with pneumatization of the pterygoid processes ( P <0.01). In both sexes, a positive correlation was found between AP diameter and, respectively, length and depth of ST ( P <0.01), together with a negative correlation between volume of SS and depth of ST ( P <0.01). Lastly, in females a positive correlation was found between age and, respectively, length and depth of ST ( P <0.01). CONCLUSIONS: The present study highlighted new metrical and morphologic relationships between volume and pneumatisation of SS and diameters of ST. Knowledge of these correlations allows to understand more clearly, in the preoperative setting, the surgical working space. Further studies are needed, especially for what concerns the relationship between sellar measurements and age in females.

Microsurgical anatomy of the inferior intercavernous sinus.

PURPOSE: Intercavernous sinuses (ICSs) are physiological communications between the cavernous sinuses. The ICSs run between the endosteal and meningeal layers of the dura mater of the sella turcica. Whereas the anterior and posterior ICSs have been frequently described, the inferior ICS (iICS) has been less well studied in the literature; however, poor awareness of the ICS's anatomy can lead to serious problems during transsphenoidal, transsellar surgery. The objective of the present anatomical study was to describe the iICS in detail. METHODS: The study was carried out over a 6-month period in a university hospital's anatomy laboratory, using brains extracted from human cadavers. The brains were injected with colored neoprene latex and dissected to study the iICS (presence or absence, shape, diameter, length, distance between inferior and anterior ICSs, distance between inferior and posterior ICSs, relationships, and boundaries). RESULTS: Seventeen cadaveric specimens were studied, and an iICS was found in all cases (100%). The shape was variously plexiform (47.1%), filiform (35.3%), or punctiform (17.6%). The mean ± standard deviation diameter and length of the iICS were 3.75 ± 2.90 mm and 11.92 ± 2.96 mm, respectively. The mean iICS-anterior ICS and iICS-posterior ICS distances were 5.36 ± 1.99 mm and 7.03 ± 2.28 mm, respectively. CONCLUSION: The iICS has been poorly described in the literature. However, damage to the iICS during transsphenoidal, transsellar surgery could lead to serious vascular complications. A precise radiological assessment appears to be essential for a safe surgical approach.

Quantitative anatomical comparison of transnasal and transcranial approaches to the clivus.

BACKGROUND AND OBJECTIVE: The clivus was defined as "no man's land" in the early 1990s, but since then, multiple approaches have been described to access it. This study is aimed at quantitatively comparing endoscopic transnasal and microsurgical transcranial approaches to the clivus in a preclinical setting, using a recently developed research method. METHODS: Multiple approaches were performed in 5 head and neck specimens that underwent high-resolution computed tomography (CT): endoscopic transnasal (transclival, with hypophysiopexy and with far-medial extension), microsurgical anterolateral (supraorbital, mini-pterional, pterional, pterional transzygomatic, fronto-temporal-orbito-zygomatic), lateral (subtemporal and subtemporal transzygomatic), and posterolateral (retrosigmoid, far-lateral, retrolabyrinthine, translabyrinthine, and transcochlear). An optic neuronavigation system and dedicated software were used to quantify the working volume of each approach and calculate the exposure of different clival regions. Mixed linear models with random intersections were used for statistical analyses. RESULTS: Endoscopic transnasal approaches showed higher working volume and larger exposure compared with microsurgical transcranial approaches. Increased exposure of the upper clivus was achieved by the transnasal endoscopic transclival approach with intradural hypophysiopexy. Anterolateral microsurgical transcranial approaches provided a direct route to the anterior surface of the posterior clinoid process. The transnasal endoscopic approach with far-medial extension ensured a statistically larger exposure of jugular tubercles as compared with other approaches. Presigmoid approaches provided a relatively limited exposure of the ipsilateral clivus, which increased in proportion to their invasiveness. CONCLUSIONS: This is the first anatomical study that quantitatively compares in a holistic way exposure and working volumes offered by the most used modern approaches to the clivus.

Expanded endoscopic endonasal approach for extending suprasellar and third ventricular lesions.

BACKGROUND: Expanded endonasal approaches can provide direct access to the midline skull base from the anterior cranial fossa to the ventral foramen magnum. Surgical strategies of bone drilling, dural opening, and intradural dissection can determine the area of surgical exposure and instrument handling, affecting the safety of devascularizing/debulking suprasellar tumors. METHODS: We describe an expanded endoscopic endonasal approach for suprasellar lesions, with stepwise image-guided dissections highlighting surgical pearls and pitfalls to enhance surgical safety. This article presents transnasal intra-third-ventricular anatomy from trans-tuber cinereum, and trans-lamina terminalis approaches, comparing subchiasmatic and suprachiasmatic trajectories. CONCLUSION: The rostral extension via endoscopic endonasal transsellar-transtubercular-transplanum approaches can provide a safe and feasible route for suprasellar lesions, in subchiasmatic, suprachiasmatic, and intraventricular regions.

Endoscopic anatomy of the sellar barrier: From the anatomical model to the operating room.

BACKGROUND: The sellar barrier concept reflects the association between the components of the roof of the pituitary fossa and the risk of intraoperative cerebrospinal fluid (CSF) leak in the surgery of pituitary adenomas. We based our concept in previous reports on the microsurgical anatomy of the pituitary fossa's superior wall. However, proof of the usefulness of this concept in endoscopic approaches is yet missing. The aim of this study was to describe the endoscopic anatomy of the sellar barrier and its subtypes in a laboratory setting and to provide evidence of its clinical usefulness. METHODS: We provided anatomical models in six fresh-frozen head and neck specimens. We performed an endoscopic endonasal approach and recreated a pathological model of each possible subtype of sellar barrier. To demonstrate the usefulness of this model in clinical practice, we conducted a prospective study including all patients with pituitary adenoma operated by an endoscopic approach between June and July 2019. RESULTS: We successfully recreated the models for each subtype of sellar barrier. When analyzing the clinical cases, we found that intraoperatively, 73.69% (14) had a strong sellar barrier; 21.05% (4) had mixed sellar barrier, and 5.26% (1) had weak sellar barrier. We recorded one case of intraoperative CSF leak in a patient with a weak sellar barrier by magnetic resonance imaging. CONCLUSION: We described the endoscopic anatomy of the sellar barrier and we recreated the three subtypes in anatomical models. We also identified these subtypes in a series of clinical cases, proving its clinical usefulness.

Three-dimensional assessment of the sella turcica: comparison between cleft lip and palate patients and skeletal malocclusion classes.

PURPOSE: The main aim of the present study was to investigate the dimensions and morphological appearance of the sella turcica in cleft lip and palate patients using cone-beam computed tomography (CBCT) images, compared to non-cleft individuals. METHODS: CBCT images of 40 (20 females and 20 males) cleft lip and palate patients and 60 (27 males and 33 females) non-cleft individuals were assessed, retrospectively. The linear dimensions (depth, diameter and length) of the sella turcica and inter-clinoid distance were measured. Sella turcica shapes were examined in the cleft lip and palate patients and non-cleft individuals. Non-cleft individuals were divided into skeletal malocclusion classes. All variables were analyzed using the Kruskal-Wallis test, Mann-Whitney U tests and Chi-square test. RESULTS: No significant difference was observed between individuals with and without cleft in the linear dimensions (depth, diameter and length) of the sella turcica (p > 0.05). However, a significant difference was found in the inter-clinoid distance between patients with cleft and non-cleft individuals (p < 0.05). Comparison of the sella turcica shape between skeletal malocclusion classes and patients with cleft showed significant differences (p < 0.05). CONCLUSIONS: No significant difference was determined in the depth, diameter, or length of the sella turcica in cleft patients when compared with non-cleft individuals. The inter-clinoid distance was lower in cleft patients than in non-cleft individuals, and this difference was statistically significant.

Assessment of the relationship between size, shape and volume of the sella turcica in class II and III patients prior to orthognathic surgery.

PURPOSES: The main purpose of this study was to assess the measurements and shape of the sella turcica by using cone beam computed tomography (CBCT) and to associate the data to skeletal class II and class III patients, including correlations with gender, age and measurements of the anterior cranial base. MATERIAL AND METHODS: A trained examiner specialist in dental radiology selected and evaluated randomly 95 CBCT images of pre-orthognathic surgery patients, 60 (63.2%) being female and 35 (36.8%) male with age between 16 and 57 years. All images were evaluated to determine the size, shape and volume of the sella turcica. The anterior cranial base, represented by the S-N line (sella-nasion), was also measured. RESULTS: Of these 95 patients, 48 (50.5%) had class III facial skeletal pattern, whereas 47 (49.5%) had class II. No statistically significant differences were found between class II and class III patients in the measurements and shape of the sella turcica (P > 0.05). The diameter and volume of the sella turcica had higher values in female patients, whereas the measurements of the anterior cranial base were higher in males (P < 0.05). CONCLUSION: Therefore, one can conclude that measurements of the sella turcica are not reliable parameters to evaluate whether a class II or class III patient will or will not need orthognathic surgery.

Morphology, Incidence of Bridging, Dimensions of Sella Turcica, and Cephalometric Standards in Three Different Racial Groups.

This study aims to assess the morphological appearance, incidence of bridging, linear dimensions of sella turcica and establish cephalometric standards in Bosnian, Chinese and Nepalese subjects. This retrospective study examined digital standardized lateral cephalograms of 540 subjects, which consisted of 116 females and 64 males with an age range of 8 to 28 years. The sella morphology, bridging, and size were analyzed on the lateral cephalograms. Steiner's and Rickett's analyses were performed on 270 subjects. Sella turcica presented a normal morphology in most Bosnian (86.7%), and Nepalese (90%) subjects whereas flat-shaped morphology was highly prevalent among Chinese subjects (36.7%). The frequency of full bridging was 7.2%, 2.8%, and 11.7% for Bosnian, Chinese, and Nepalese subjects, respectively. A significant correlation was detected between the length of sella turcica and gender of Bosnian subjects, whereas the size of sella turcica and gender of Chinese and Nepalese subjects were not affected. A direct correlation existed between age and size of sella turcica of Bosnian subjects. A significant correlation was detected between length and diameter of sella turcica and age in Chinese and Nepalese subjects. A statistically significant difference was found in length (P < 0.001), depth (P < 0.01) and diameter (P < 0.001) of sella turcica with race. The diameter of sella turcica was the only parameter significantly associated with race, gender and age. Significant differences were found between cephalometric norms in different racial groups. These findings assist orthodontists, neurosurgeons, and forensic medical investigatiors during orthodontic treatment planning, diagnosis of pathology of the pituitary gland, and age determination.

The diaphragma sellae, diaphragm opening, and subdiaphragmatic cistern: an anatomical study using magnetic resonance imaging.

PURPOSE: Few studies have explored the detailed morphology of the diaphragma sellae (DS), diaphragm opening (DO) or stoma, and subdiaphragmatic cistern (SDC) using neuroimages. The aim of the present study was to characterize these structures using magnetic resonance imaging. METHODS: Thin-sliced, sagittal and coronal T2-weighted imaging was performed for a total of 84 outpatients. RESULTS: The DS, DO, SDC, and relevant structures were consistently delineated in all patients. In 66% of patients, all three structures appeared to be highly variable, and were classifiable as six distinct morphological types. In 4% of patients, the DS presented as a complete sheet lacking a discernible DO. In addition, 30% of the patients presented with undiscernible SDCs. In the coronal sections of 11% of patients, the pituitary glands extended laterally, reaching or extending beyond the center line on the sectional image of the cavernous internal carotid artery. CONCLUSIONS: Thin-sliced, sagittal, and coronal T2-weighted sequences are useful for delineating the DS, DO, and SDC. Morphological variation of these structures among individuals may considerably influence the direction of pituitary tumor expansion.

Cavernous Sinus and Parasellar Region: An Endoscopic Endonasal Anatomic Cadaver Dissection.

The aim of this study was to investigate the neurovascular structures of the cavernous sinus with the endonasal endoscopic transpterygoid approach on fresh human cadavers. Additionally, the course of internal carotid artery (ICA) and relevant anatomy was thoroughly investigated to refine the anatomical landmarks, exposure difficulties, potential complications, and limitations using the endonasal endoscopic technique. This study was carried out at an otolaryngology department of a tertiary medical center between June 2014 and June 2015. The surgical dissection was performed on 10 fresh human cadaver specimens using paranasal sinus and skull base endoscopic instruments. Cavernous sinuses and parasellar area were explored via an endoscopic endonasal transpterygoid approach. Dehiscence was present in 5 (25%) cavernous ICAs. Projection of the cavernous ICA on the whole lateral sphenoid wall was prominent in 6 (%30) sphenoid sinuses. Anterior curve was prominent in 12 (60%) cavernous ICAs, whereas posterior was prominent in 7 (35%). Mean distance between the lateral wall of eustachian tube orifice and petrous ICA was 19.50 ± 1.05 mm (range 18-22 mm). Cranial nerves of the cavernous sinus showed no variation. Control of the ICA is critical during the endonasal endoscopic approach to the cavernous sinus and skull base. The vidian nerve is a reliable and important landmark to the petrous ICA in the transpterygoid approach. Dissection of the eustachian tube and its relation to the ICA has to be kept in mind during nasopharyngeal surgery.

Printable 3D model of the sella turcica region including the interclinoid bridge.

The objective of the study was to create a printable 3D model of the sellar region of the sphenoid bone for demonstrating anatomical variant of the osseous bridging between anterior and posterior clinoid processes. Three-dimensional reconstruction of the middle cranial fossa along with 3D printed model, allow for accurate depicting position of the interclinoid bridge with reference to other basicranial structures.

Morphometric Analysis of Sella Turcica Using Cone Beam Computed Tomography.

OBJECTIVE: The purpose of this study was to assess morphological shape and morphometric analysis of the sella turcica using cone beam computed tomography (CBCT) in different planes of section (coronal and sagittal). MATERIALS AND METHODS: CBCT images of 177 subjects of which 51 males and 126 females in the age group of 11 to 73 years were included in the study population. Linear dimensions which include the length, depth, diameter, and interclinoid distance were measured and the shape of sella turcica was analyzed. RESULTS: Sella turcica had circular morphology in 69.5% of the subjects while flattened shape of sella turcica was observed in 16.4%, oval shape of sella turcica in 14%. There was no significant difference in the all measurements of sella turcica between males and females (P > 0.05). Diameter (P < 0.01), depth (P < 0.001), length (P < 0.05), and interclinoid distance (P < 0.05) of the sella turcica differed significantly with age. CONCLUSIONS: The anatomical structure of sella turcica can be studied effectively in CBCT images. Linear dimensions and shape of sella turcica in the current study can be used as reference standards for further investigations.

A simple and accurate craniofacial midsagittal plane definition.

INTRODUCTION: In this article, we aimed to establish an ideal definition for the craniofacial midsagittal plane (MSP) by first finding an optimal "plane of best fit" and then deriving a simple approximation for clinical use that is highly accurate. METHODS: For 60 adolescent patients, 3-dimensional coordinates of 8 central landmarks and 6 pairs of lateral landmarks were collected. Across all patients, the coplanarity of the central landmarks was compared with that of the midpoints of the lateral landmarks. The MSP of best fit was then found by minimizing the mean square distance of the 8 central landmarks to a plane. Across all patients, each possible 3-point plane was compared with the MSP of best fit with respect to both orientation and proximity. RESULTS: The central landmarks were more coplanar and thus more accurate than the midpoints of the lateral pairs. The plane defined by nasion, basion, and incisive foramen was the closest to the MSP of best fit in both orientation and proximity. CONCLUSIONS: The nasion-basion-incisive foramen plane should be used for skull orientation and 3-dimensional cephalometric analyses because it approximates the MSP of best fit with high accuracy, avoids the use of horizontal reference planes, avoids influence from upper and midface asymmetry, uses easily identifiable relevant landmarks, and is simple to define.

Evaluation of Sella Turcica Shape and Dimensions in Cleft Subjects Using Cone-Beam Computed Tomography.

OBJECTIVE: The aim of this study was to assess the morphology of the sella turcica and measure its size in cleft and noncleft subjects. MATERIAL AND METHODS: Cone-beam computed tomography (CBCT) images of 54 individuals (29 males; 25 females) with cleft and 85 (22 males; 63 females) without cleft were used for this study. Syndromic patients with cleft(s) were not included because of possible additional endocrinological and/or morphological disorders. Linear measurements included length, depth, and diameter. The shape of the sella turcica was analyzed in the cleft and noncleft groups. An independent t test was conducted to evaluate differences between genders and groups. One-way ANOVA was used to compare age groups. RESULTS: The length (p < 0.001) of the sella turcica was smaller in noncleft subjects than in cleft subjects. Diameter (p = 0.014) and depth (p = 0.005) showed as constantly increasing from an age <15 to >25 years in the overall assessment. The distribution of the shape of the sella turcica differed significantly between groups (p < 0.001). CONCLUSIONS: In this study, CBCT was used to assess the morphology of the sella turcica. A majority of the subjects with cleft had a flattened sella turcica compared to that of the control group. A shorter length of the sella turcica was more evident in the cleft subjects than in the control group.

A Cephalometric Analysis on Magnitudes and Shape of Sella Turcica.

Familiarity with the shape and dimensions of sella turcica is important to recognize and manage pathological conditions of pituitary gland as well as for orthodontic treatment planning. The present study aims to describe the morphology and dimensions of sella turcica from Indian population, using lateral cephalograms to set a reference data for comparison among different races. The study used 36 lateral skull radiographs of both sexes between age group of 13 to 18 years. Shape of sella turcica was noted by visual inspection. Length, height anterior, height median, height posterior, distance between frontonasal suture and mental spine to midpoint of posterior clinoid process, and tuberculum sella were measured using digital vernier caliper with reference to Frankfort line. The results of the study revealed that mean length, height anterior, height median, height posterior were larger in females than in males. The morphological types identified include pointed posterior clinoid process with rounded hypophyseal fossa, hooked posterior clinoid process with rounded hypophyseal fossa, hooked posterior clinoid process with flask-shaped hypophyseal fossa. These observations would be beneficial for the clinicians and orthodontists to design treatment planning in pathology of pituitary gland and in correcting dentofacial anomalies.

Sella turcica: an anatomical, endocrinological, and historical perspective.

INTRODUCTION: The sphenoid bone has a superior depression called the sella turcica, Latin for "Turkish saddle," where the pituitary gland is found. The availability of modern radiological imaging techniques has replaced plain radiography of the sella turcica in the investigation of hypothalamo-pituitary abnormalities. However, the size of the sella turcica, and smaller sella turcica size in particular, may cause pituitary dysfunction because of the changes in the structure of pituitary gland or may be associated with some genetic or acquired endocrine disorders. The name "sella turcica" is one of the most commonly used terms in everyday endocrine practice. METHODS: In this review, after a brief explanation of the anatomical and endocrinological features of the sella turcica had been given, a historical perspective of sella turcica nomenclature was presented for the first time. FINDINGS AND CONCLUSIONS: After Andreas Vesalius's description of it as a suitable cavity for the gland that receives the "phlegm of the brain" in De Humani Corporis Fabrica (1543), medical scholars began to use seat/saddle-related terms such as the ephippium, pars sellaris, sella equina, sella ossis, and sella sphenoidalis. The real designation of the sella turcica, however, was introduced to the anatomical nomenclature by the anatomist Adrianus Spigelius (1578-1625) in his famous work De Corpora Humanis Fabrica (1627).

Utility of three-dimensional computed tomography for anatomical assistance in endoscopic endonasal transsphenoidal surgery.

Endoscopic endonasal transsphenoidal surgery (ETSS) has been widely applied to pituitary adenomas. However, anatomical orientation is difficult when structures of the sphenoidal sinus are complicated. This study investigated the usefulness of three-dimensional computed tomography (3D-CT) modeling in planning surgical procedures for ETSS and providing anatomical guidance during surgery. CT data from 99 consecutive patients with pituitary adenoma treated between January 2008 and March 2014 were used to reconstruct 3D-CT models. Based on these images, the architecture of sphenoidal sinus, particularly structures surrounding the sellar floor, was visualized for preoperative simulation of surgical procedures. These 3D-CT images were also compared to surgical views during ETSS to evaluate applicability of the images. These models clearly demonstrated the morphology of the nasal cavity and structures of the sphenoidal sinus, including bony prominences of the internal carotid arteries (ICAs) and optic canals by successively eliminating sphenoidal structures. The 3D-CT images permitted determination of the maximum marginal line of the opening of the sellar floor by presenting vital structures such as ICAs and optic canals. With this 3D-CT model, the surgeon could access the sella more easily, open the floor widely enough for each individual patient, and resect the tumor maximally without complications. Preoperative 3D-CT models distinctly visualized the optic canals, bilateral ICAs, and complicated structures of sphenoidal septa. The 3D-CT images were useful for preoperative planning and as a road map during endoscopic surgery for pituitary adenoma, facilitating maximum tumor resection without complications.

Anatomical features of skull base and oral cavity: a pilot study to determine the accessibility of the sella by transoral robotic-assisted surgery.

The role of transoral robotic surgery (TORS) in the skull base emerges and represents the natural progression toward miniinvasive resections in confined spaces. The accessibility of the sella via TORS has been recently described on fresh human cadavers. An anatomic study is mandatory to know if this approach would be feasible in the majority of patients regardless of their oral morphological features. From 30 skull base CT scans from patients who were asked to open their mouth as wide as they can, we measured specific dimensions of the oral cavity and the skull base, such as length of the palate, mouth opening and distance from the sella to the palate. All data were acquired on a sagittal midline plane and on a 25° rotation plane, which simulated the axis of the robotic instruments. Looking at the projection of the dental palatine line on the sella, we studied possible predictive factors of sellar accessibility and tried to bring objective data for surgical feasibility. We also proposed an angle α to study the working angle at the skull base. We observed that the maximal mouth opening was a good predictive factor of sellar accessibility by TORS (p < 0.05). The mouth aperture threshold value for a good sensitivity, over 80 %, was comparable to the mean value of mouth opening in our series, 38.9 and 39.4 mm respectively. Moreover, we showed a statistically significant increase of the working angle α at the skull base comparing the lateral access to the midline one (p < 0.05). This seemed to quantitatively demonstrate that the robotic arms placed at the labial commissure of the mouth can reach the sella. From these anatomical features and previous cadaveric dissections, we assume that TORS may be feasible on a majority of patients to remove pituitary adenomas.

Anatomical study of posterior clinoid process (PCP) and its clinical meanings.

PURPOSE: The aim of this study is to provide a new and comprehensive anatomic study of the posterior clinoid process (PCP) as well as data for PCP location to guide the surgeons in endoscopic surgery. MATERIALS AND METHODS: Computed tomography angiography images of 120 PCPs and structures around them in adults were reviewed. The measurement was on coronal, sagittal, and axial planes after multiplanar reconstruction. The length, width, and thickness were accessed for the best understanding of the feature of PCP. The distance from the base of the PCP and the middle lowest point of the sellar floor was measured to find the position of the PCP during the transphenoid approach. RESULT: PCP varies in width and thickness in different portions of it and is closely related to the internal carotid artery and posterior communicating artery, which makes it an important landmark during surgery. CONCLUSION: The shape of PCP is various, and the analysis of its relationship to the important structures around it is of great value. In addition, the preoperative radiological evaluation plays a major role in patients considered for endoscopic sinus surgery. Detailed preoperative analysis of the anatomy of the sphenoid sinus and its boundaries is crucial in facilitating entry to the pituitary fossa and reducing intraoperative complications.