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Table of Contents
ORIGINAL ARTICLE
Year : 2020  |  Volume : 69  |  Issue : 3  |  Page : 144-149

The measurement indexes and the relationships with adjacent structures of vidian canal and foramen rotundum using computed tomography


1 Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Hatay Mustafa Kemal University, Hatay, Turkey
2 Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey
3 Department of Dentomaxillofacial Radiology, Gulhane Faculty of Dentistry, Health Sciences University, Ankara, Turkey

Date of Submission06-Apr-2020
Date of Acceptance22-May-2020
Date of Web Publication30-Sep-2020

Correspondence Address:
Dr. Gozde Serindere
Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Hatay Mustafa Kemal University, 31060 Hatay
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JASI.JASI_56_20

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  Abstract 


Introduction: The aim of this study was to evaluate vidian canal (VC) and foramen rotundum (FR) and their anatomical relationships with adjacent structures using computed tomography (CT) in a Turkish subpopulation. Material and Methods: CT images of 150 patients were retrospectively evaluated. Various morphometric measurements (distance from FRs to midline, distance from FR to VC, position and angle of FR, and types of FR and VC) were performed from both left and right sides on CT scans. Results: One hundred and fifty patients with a mean age of 41.06 ± 17.812 years were included in this study. The mean distance from midline to right FR was 17.89 ± 1.94 and 18 ± 1.83 in females and males, respectively. The mean distance from midline to left FR was 18.33 ± 1.94 and 19 ± 2.18 in females and males, respectively. Twenty-three cases had Type 1 VC and 40 and 112 cases had Type 2 and 3 VCs, respectively. Three patients had Type I FR, 25 and 57 patients had Type IIa and IIb, respectively, and 93 patients had Type III FR. The position of FRs regarding the base of lateral pterygoid plate was online in 77 patients, medially placed in 92 patients, and laterally placed in 12 patients. Discussion and Conclusion: It is important to know sphenoid sinus and neighboring anatomical structures for planning of endoscopic skull base surgery because it is located close to some important anatomical structures such as internal carotid arteries, optic nerve, and cranial nerves. Surgeons should be careful in preoperative treatment planning and also during the operation.

Keywords: Computed tomography, foramen rotundum, sphenoid sinus, vidian canal


How to cite this article:
Serindere G, Gunduz K, Avsever H. The measurement indexes and the relationships with adjacent structures of vidian canal and foramen rotundum using computed tomography. J Anat Soc India 2020;69:144-9

How to cite this URL:
Serindere G, Gunduz K, Avsever H. The measurement indexes and the relationships with adjacent structures of vidian canal and foramen rotundum using computed tomography. J Anat Soc India [serial online] 2020 [cited 2020 Oct 25];69:144-9. Available from: https://www.jasi.org.in/text.asp?2020/69/3/144/296912




  Introduction Top


The sphenoid sinus has important anatomy during surgical operations of the ventral skull base that is not only the route for reaching the sellar, parasellar, suprasellar, and clival areas but also a way to Meckel's cave and the midcranial fossa. It is located close to various vital anatomical structures such as the internal carotid artery, optic nerve, and cranial nerves. The location of surgical window to the midcranial fossa is in the pterygoid body of the sphenoid bone.[1]

The foramen rotundum (FR) is a round opening of the sphenoid bone greater wing that anteriorly locates into the pterygopalatine fossa and includes the maxillary nerve;[2] it locates above and lateral to the pterygoid canal.[3] The maxillary branch of the trigeminal nerve passes through the FR [3] after crossing the midcranial fossa where it is in relation to the cavernous sinus lateral wall.[4]

The vidian canal (VC), nerve, and artery are named after Vidius. Vidius was a Medicine Professor at the College of France, and he was a physician to the King of France in the middle of the 16th century.[5],[6] The VC may be observed at the skull base at the anterior border of the foramen lacerum and may locate above and between the pterygoid plates of the sphenoid bone. It enters the pterygopalatine fossa and contains the Vidian nerve, artery, and vein. The Vidian nerve arises from the union of postganglionic sympathetic fibers of the deep petrosal nerve of the carotid plexus and preganglionic parasympathetic fibers from the greater petrosal nerve. After entering the pterygopalatine fossa through the VC, the Vidian nerve enters the posterior area of the pterygopalatine ganglion. The sympathetic fibers provide the vascular constriction in the nasal cavity, and the parasympathetic fibers are responsible for the mucosal secretions in the oral and nasal cavity and the pharynx.[7],[8]

The sphenoid sinus is the most difficult to reach the paranasal sinuses.[9] In close relationship, there are several vital anatomical structures such as internal carotid artery, optic nerve, and VC. Physicians dealing with skull base surgery must know the important anatomical structures in the skull base. In surgical procedures performed with insufficient anatomical information, complications are inevitable.[10],[11] Imaging modalities are important for the treatment of skull base disorders because clinical evaluation of this region is frequently difficult. Computed tomography (CT) is an ideal choice to evaluate anatomy and is frequently combined with magnetic resonance imaging.[12]

The aim of this study was to evaluate the measurement indexes of FR and VC and also their relationships with the adjacent structures on CT scans.


  Material and Methods Top


Study design

Before starting the study, ethical approval was obtained from the Local Ethics Committee of Hatay Mustafa Kemal University (Decision date: January 16, 2020, decision number: 07). Images of 150 patients (71 females and 79 males; mean age: 41.06) who applied to the Department of Dentomaxillofacial Radiology were selected from the database. Patients under 18 years of age, or patients with known skull base pathology, remarkable rhinosinusitis (inflammatory changes that prevent the visualization of the skull base anatomy), maxillofacial fractures, sinonasal tumors, or polyposis, were excluded from the study. One hundred and fifty CT images that met the inclusion criteria were evaluated retrospectively.

CT machine (Toshiba Aquilion, Toshiba Medical Systems, Otawara, Japan) was used for all the CT procedures. A routine protocol was performed. All evaluations were performed by a 15.6-inch full HD notebook with resolution of 1920 × 1080 pixels and by a single observer (GS) who had 6 years. Undecided situations were solved by consensus with KG who had nearly 15 years of clinical experience.

Evaluations were performed using the hospital information system (ENLIL and PACS). For standardization, the first coronal section with VC and FR seen together was selected.

The measurements of this study

An imaginary midline line perpendicular to the rostrum was identified. Various morphometric parameters were studied according to this midline [Figure 1].
Figure 1: The demonstration of various morphometric parameters (red arrow: foramen rotundum, green arrow: vidian canal, and blue arrow: lateral pterygoid plates; V: Vertical distance, H: Horizontal distance, and D: Direct distance) on the coronal computed tomography scan based on the study of Mohebbi et al.[13]

Click here to view


These measurements were performed based on the studies of Mohebbi et al. as follows:[13]

  • Distance from the midline to the right and left FRs
  • Direct distance between VC and FR on both sides
  • Horizontal distance between VC and FR on each side (distance between two vertical lines intersecting FR and VC)
  • Vertical distance between VC and FR on each side (distance between two horizontal lines intersecting VC and FR)
  • Right and left rotundum angles (were calculated as the angle between the imaginary line connecting FR to VC and the vertical line that crosses VC).


FR's position relative to the base of lateral pterygoid plate as reported by Mohebbi et al.[13] [Figure 2] was as follows:
Figure 2: Coronal computed tomography scan shows foramen rotundum localization with respect to the base of lateral pterygoid plate. (a) Online (right side) and medial (left side) (b) lateral

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  • Located online: When FR is tangent to the lateral pterygoid plate
  • Medially located: If FR is in the medial position relative to the lateral pterygoid plate
  • Laterally located: FR is lateral to the lateral pterygoid plate.


The types of FR and VC based on the study of Mohebbi et al.[13] and Lee et al.[10] [Figure 3] were as follows:
Figure 3: (1) The types of vidian canal (a) Type 1 (b) Type 2 (c) Type 3 (2) the types of foramen rotundum (a) Type I (b) Type IIa (c) Type IIb (d) Type III

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  • VC was divided into three types on CT:


    • Type 1 – VC is completely in the sphenoid sinus
    • Type 2 – When the VC is on the floor of the sphenoid sinus or partially protrudes into the sphenoid sinus
    • Type 3 – VC fully embedded in the sphenoid corpus.


  • FR was divided into three types on CT:


    • Type I – FR is completely localized in the sinus cavity
    • Type IIa – FR is partially localized in the sinus cavity or partially protruding into the sphenoid sinus
    • Type IIb – When FR is tangent to the sinus wall
    • Type III – FR is completely inside the sphenoid bone.


Statistical analysis

SPSS version 22 software (SPSS Inc., Chicago, IL, USA) was used to enter and analyze data. All analyses have been done with SPSS version 22 software at an error level of 0.05. The quantitative variables which included distances were expressed as standard deviation and mean. Statistical significance between right and left distances was determined using paired t-test and Student's t-test. According to the null hypothesis, there was no difference between the groups tested. P < 0.05 was defined as significant.

To study relationship between three qualitative variables of FR-online located, FR-medial, and FR-lateral, the Chi-squared test and Fisher's exact test was used. The relationship between variable of age and all individual quantitative variables was examined with Pearson correlation test. Since the sample size was below 30 at some levels of the qualitative variables and also reached below 5 at some levels of qualitative variables, the age variable distribution was not normal at some levels of qualitative variables with the sample size of below 30. Therefore, the Kruskal–Wallis nonparametric test was used to study the relationship between variable of age and all individual qualitative variables. An Independent t-test was used to examine the difference in the variables measuring the right and left sides according to gender. The Chi-squared test was used to examine the relationship between gender and all qualitative variables.

Due to the large sample size and based on the central limit theorem, the average distribution of quantitative variables is approximately normal.


  Results Top


The research participants have a mean age of 41.06 ± 17.812. Seventy-one (47.3%) females and 79 (52.7%) males were included in this study. [Table 1] and [Table 2] report the descriptive statistics for the quantitative and qualitative variables according to gender, respectively. There was a significant difference in the distance from midline to right and left FR, horizontal, vertical, and direct distances from the right and left FRs to VCs (P < 0.05). There was no difference between the variables FR-online located and FR-medial (P > 0.05). There was a significant difference between the variables Type 1 VC and Type 3 VC. There was a significant relationship between the variables Type 2 VC and Type 3 VC (P < 0.05). There was a significant difference between the variables Type IIb FR and Type III FR (P < 0.05) [Table 3]. P value between some variables, as shown in [Table 3], could not be calculated because the cells of the Chi-squared test were all zero.
Table 1: Descriptive statistics for the quantitative variables according to gender

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Table 2: Descriptive statistics for the qualitative variables according to gender

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Table 3: Relationships between variables analyzed by different statistical tests stated in the results section of the article

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Pearson correlation test and Kruskal–Wallis test results are reported in [Table 3]. There was no significant relationship between age and all individual quantitative variables (P > 0.05).

[Table 3] shows that there was a significant difference in age among three levels of left, right, and bilateral localizations of qualitative variables of FR-online, FR-medial, Type 2 VC, Type 3 VC, Type IIb FR, and Type III FR. No significant difference was found in age at levels of other qualitative variables (P > 0.05).

There was a significant difference between gender and the distance from midline to left FR and right rotundum angle (P < 0.05), and no significant difference was found between the other parameters and gender (P > 0.05). There was no difference between each of the variables and gender (P > 0.05) [Table 3].


  Discussion Top


Although there are some studies on VC in the literature, to our knowledge, no such detailed studies about the radioanatomic relationship of VC and FR with adjacent anatomical structures have been found except one study reported by Mohebbi et al.[13]

Measurement values in our study were lower than those of Mohebbi et al.[13] It was reported by Mohebbi et al.[13] that the position of FRs was online in 50% of cases, medially placed in 47%, and laterally placed in 3% of cases. In our study, the case numbers of medially placed FR were higher than online placed, and the incidence of laterally placed FR was higher according to the study of Mohebbi et al.[13] In addition, in their study, it was found that 28 cases (28%) had Type 1 VC and 48% and 24% had Type 2 and 3 VCs, respectively. Four patients (4%) had Type I FR, 28% and 44% had Type IIa and IIb, respectively, and 24% had Type III FR.[13] In our study, all percentages were found to be lower except the percentage of Type 3 VC and FR. Furthermore, they reported the distance from FR to midline as 19.00 ± 2.07 mm in the right side and 19.34 ± 2.17 mm in the left side. In the right side, horizontal, vertical, and direct distances from FR to VC were reported as 5.89 ± 2.4 mm, 5.06 ± 2.03 mm, and 8.16 ± 2.27 mm, respectively. In the left side, horizontal, vertical, and direct distances from FR to VC were reported as 5.93 ± 2.13 mm, 5.49 ± 2.13 mm, and 9.20 ± 2.15 mm, respectively. Right and left FR angles were reported as 46.76 ± 12.32 and 46.40 ± 10.67, respectively.[13] All values of this study were lower than the study of Mohebbi et al.[13]

Kasemsiri et al.[11] reported the average distance from midline to left FR 19.11 mm and to right FR 17.67 mm. Close results were found in this study. Mohebbi et al.[13] reported that the average distance of midline to left FR was found to be significantly more than to right FR. The average horizontal and vertical distances from FR to VC in Kasemsiri's study [11] showed no significant difference between right and left sides, as the same result in the study of Mohebbi et al.[13] In our study, there was a significant difference in the distance from midline to right and left FR and horizontal, vertical, and direct distances from the right and left FRs to VCs.

Yeǧin et al.[14] reported that VC in females was found in 31.5%, 32%, and 36.5% belonging to Types 1, 2, and 3, respectively. VC in males was found in 32.2%, 28.6%, and 39.1% belonging to Types 1, 2, and 3, respectively. In our study, VC in females was found in 15.5%, 36.6%, and 67.6% belonging to Types 1, 2, and 3, respectively. VC in males was found in 15.2%, 17.7%, and 81% belonging to Types 1, 2, and 3, respectively. The reason for some high results in our study may be the calculation of percentages of men and women among themselves, not by total number.

According to the cone-beam CT study of Bahşi et al.,[15] it was reported that VC totally protruded into the sphenoid sinus (19.75%), partially protruded into the sphenoid sinus (44.37%), and embedded inside bony tissue of the body of sphenoid bone (35.87%). We can say that there are lower results in our study except the incidence of Type III FR.

Yazar et al.[16] reported the mean distance from FR to VC as 7.2 mm. As can be seen, the results of this study were lower than the results in the studies we discussed. We think that this result depends on the subpopulation we are working on.

Nowadays, less invasive endoscopic surgery is frequently performed for treating several diseases of paranasal sinuses.[14] Surgical excision of pituitary tumors is frequently performed with endoscopic transsphenoidal approach.[17] The paranasal sinuses have several anatomical variations. Appropriate information of these variations before the surgical operations using CT is fundamental to decrease the complications and to prevent the injury of important structures.[18] Several vital anatomical structures have a relationship with sphenoid sinus such as VC and FR.[9]


  Conclusion Top


Although there are studies related to the anatomical and radiological evaluation of VC in the literature, there is no comprehensive radiographic anatomical study in which VC and FR were evaluated together, except for the study of Mohebbi et al.[13] We think that this situation will increase the value of our study, can be a motivation source for other authors who are interested in this subject, and can make useful contributions to the literature.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Tubbs RS, Hill M, May WR, Middlebrooks E, Kominek SZ, Marchase N, et al. Does the maxillary division of the trigeminal nerve traverse the cavernous sinus? An anatomical study and review of the literature. Surg Radiol Anat 2008;30:37-40.  Back to cited text no. 4
    
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Yeǧin Y, Çelik M, Altıntaş A, Şimşek BM, Olgun B, Kayhan FT. Vidian canal types and dehiscence of the bony roof of the canal: An anatomical study. Turk Arch Otorhinolaryngol 2017;55:22-6.  Back to cited text no. 14
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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