Imaging anatomy of the vidian canal and its clinical significance

Abstract

Background: Vidian neurectomy (VN) is an effective surgical treatment for severe allergic rhinitis (AR). However, little research has been conducted on the imaging anatomy of the vidian canal (VC). This study aimed to analyze the computed tomography (CT) imaging of the VC and its surrounding structures and investigate the morphometric characteristics and clinical significance of VN.

Methods: We analyzed 118 paranasal sinus CT scans (55 male and 63 female patients), with axial, coronal, and sagittal slices being used in the study.

Results: Among the 118 patients in this study, the average length of the VC in male and female patients was 14.00±3.35 and 12.51±3.42 mm, respectively; the transverse diameter of the posterior segment of the VC in females was larger than that in males; and the length of the VC and the distance between VC and foramen rotundum (FR) in males were longer than those in females. The angle between the VC and the sagittal plane and the angle between the sphenopalatine foramen (SPF) and the VC in females were larger than those in males, and the distance between the attachment to the end of the middle turbinate (MT) and the VC was greater. Type 2 VC occupied a dominant position. The VC was mostly at the same line as the medial wall of the maxillary sinus (MS) and was located on the medial side of the medial pterygoid plate (MPTG). The highest point of the VC was mostly superior to that of the palatovaginal canal (PVC). Most of the VC was inferior to the internal carotid artery (ICA), and no cases were observed in which the VC was above the ICA. Some of the measurements of the VC and its surrounding structures were correlated.

Conclusions: The position and morphometric information of the VC could be reflected in a CT scan, which may contribute to the evaluation of VN preoperatively and postoperatively.

Keywords: Allergic rhinitis (AR); anatomical variation; computed tomography image (CT image); vidian neurectomy (VN).

Figure 1

Endoscopic findings in VN. Yellow arrow: the anterior opening of the VC; white arrow: MPTG; blue arrow: PVC. VN, vidian neurectomy; VC, vidian canal; MPTG, medial pterygoid plate; PVC, palatovaginal canal.

Figure 2

Definition and measurement of different values. (A) Axial slices (level of the vidian canal): the diameter of the anterior [1], central [2], and posterior [3] segment of the VC; the length of the VC [4]; the transverse diameter of the SPF [5]; the distance between the medial border of the anterior boundary of the VC to the posterior boundary of the SPF [6]; the angle between the axis of the SPF to the axis of the VC [7]; the angle between the axis of the SPF and the VC [8]; the angle between the axis of the PVC and the VC [9]. (B,C) The axial slices (level of the vidian canal) with a horizontal line drawn past the posterior wall of the MS to determine the distance from the MS to the VC [10] and a horizontal line drawn past the attachment of the end of the middle turbinate to determine the distance from the MT to the VC [11]. (D) Coronal slices (level of the vidian canal): shortest distance between the VC and the FR [12]. A, anterior; P, posterior; R, right; L, left (in A and D); MS, maxillary sinus; ITF, infratemporal fossa; L, lateral (in B and C); M, medial; S, superior; I, inferior; SS, sphenoid sinus; VC, vidian canal; SPF, sphenopalatine foramen; PVC, palatovaginal canal; MT, middle turbinate; FR, foramen rotundum.

Figure 3

Axial slices with a straight line drawn along the medial wall of the MS and the position of the VC being identified as lateral (A), online (B), or medial (C) to the medial wall of the MS. P, posterior, MS, maxillary sinus; VC, vidian canal.

Figure 4

The coronal slices (level of the anterior boundary of the vidian canal) with a horizontal line drawn past the highest point of the PVC and the position of the VC being identified as inferior, at, or superior to the PVC. The yellow arrows indicate VC, and the green arrows indicate PVC. SS, sphenoid sinus; PVC, palatovaginal canal; VC, vidian canal.

Figure 5

The coronal slices (level of the anterior boundary of the vidian canal) with a straight line drawn along the MPTG and the VC identified as medial (A), online (B), or lateral (C) to the MPTG. I, inferior; MPTG, medial pterygoid plate; VC, vidian canal.

Figure 6

Coronal slices centered on the terminal aspect of the VC (green arrow) and the VC being identified as inferior, at, or superior to the pICA (green circle). S, superior; I, inferior; SS, sphenoid sinus; VC, vidian canal; pICA, petrous internal carotid artery.

Figure 7

Coronal slices of the type 1 (A), type 2 (B), and type 3 (C) VC (yellow arrow). SS, sphenoid sinus; VC, vidian canal.

Figure 8

The sagittal slices with a straight line drawn along the posterior wall of the sphenoid sinus showing SS (A) type II (presellar), (B) type III (sellar), and (C) type IV (postsellar). SS, sphenoid sinus.

Figure 9

Coronal slices with a straight line drawn along the medial wall of the MS and the variation of the posterior ethmoid cells being identified as RMC (A), EMS (B), or Haller cells (C). RMC, retromaxillary air cell; MS, maxillary sinus; EMS, ethmomaxillary sinus; H, Haller cell.

Figure 10

Correlation analysis of the measurements conforming to a normal distribution and simple linear regression analysis of the measurements with P<0.05 in the correlation analysis. (A) Correlation analysis of the anterior diameter of the VC, the central diameter of the VC, the posterior diameter of the VC, the length of the VC, the angle between the VC and the sagittal plane, the transverse diameter of the SPF, the distance from the VC to the SPF, the angle between the axis of the SPF and the VC, the distance from the posterior wall of the MS to the VC, the distance from the attachment of the end of the MT to the VC, the distance from the attachment of the end of the MT to the posterior wall of the MS (the distance from the posterior wall of the MS to the VC subtracted from the distance from the attachment of the end of the MT to the VC), the angle between the axis of the PVC and the VC, and the distance between the VC and the FR. The Spearman ρ value of each pair of terms is shown in the square grid. The red to blue bar in the right of the figure indicates the ρ value from 1.0 to −1.0. Blank boxes indicate that the P value of the correlation analysis between the 2 terms was greater than 0.05 and that the ρ value could not thus be obtained. (B) Linear correlation of the angle between the VC and the sagittal plane and the angle between the axis of the SPF and the VC. (C) Linear correlation of the angle between the VC and the sagittal plane and the angle between the axis of the PVC and the VC. (D) Linear correlation of the angle between the VC and the distance from the posterior wall of the MS to the VC. (E) Linear correlation of the distance from the attachment of the end of the MT to the posterior wall of the MS. (F) Linear correlation of the distance from the VC to the SPF and the axis of the PVC and the VC. (G) Linear correlation of the distance from the VC to the SPF and the distance between the VC and the FR. (H) Linear correlation of the distance from the VC to the SPF and the distance from the posterior wall of the MS to the VC. (I) Linear correlation of the distance from the VC to the SPF and the distance from the attachment of the end of the MT to the VC. (J) Linear correlation of the angle between the axis of the SPF and the VC and the angle between the axis of the PVC and the VC. (K) Linear correlation of the angle between the axis of the SPF and the VC and the distance from the attachment of the end of the MT to the VC. (L) Linear correlation of the angle between the axis of the SPF and the VC and the distance from the attachment of the end of the MT to the posterior wall of the MS. VC, vidian canal; SPF, sphenopalatine foramen; MS, maxillary sinus; MT, middle turbinate; PVC, palatovaginal canal; FR, foramen rotundum.