Morphological CBCT parameters for an accurate differentiation between nasopalatine duct cyst and the normal nasopalatine canal

Abstract

Background: The incisive foramen width was a traditional imaging criterion for diagnosing nasopalatine duct (NPD) cysts. Recent CBCT studies demonstrated significant dimensional variations of the nasopalatine canal, which raised questions about the accuracy of this criterion. This study investigated whether nasopalatine canal diameters assessed on CBCT images can accurately differentiate NPD cysts from normal nasopalatine canals.

Methods: The study included 19 patients with NPD cysts (12 (63.2%) males, 7 (36.8%) females, mean age 44.7 ± 13.3), and a control group of 164 patients (72 (43.9%) males, 92 (56.1%) females, mean age 47.25 ± 17.74). CBCT images were retrospectively evaluated. The following nasopalatine canal diameters were measured on reference sagittal, coronal, and axial reformation images: nasal opening anteroposterior (AP) and mediolateral (ML) diameter, oral opening AP (APOO) and ML (MLOO) diameter, nasopalatine canal length, minimum ML (minML) diameter, anterior wall expansion (AWE), nasopalatine canal angle, and the mid-level AP diameter (midAP). All parameters were compared between groups. Discriminant functional analysis (DFA) was applied to detect CBCT parameters that best differentiate the NPD cyst from the normal canal.

Results: Patients with NPD cyst had significantly greater values of APOO (7.06 ± 2.09 vs. 5.61 ± 1.70), MLOO (6.89 ± 2.95 vs. 3.48 ± 1.24), minML (2.88 ± 1.53 vs. 2.25 ± 1.09), AWE (2.15 ± 0.65 vs. 0.41 ± 0.67), and midAP (4.58 ± 1.61 vs. 2.48 ± 0.96). DFA showed MLOO, AWE, and midAP as the most accurate in distinguishing NPD cyst from the normal canal. When combined in the discriminant function equation X = 0.390·MLOO + 1.010·AWE + 0.288·midAP (cut score 1.669), the differentiation can be performed with a sensitivity and specificity of 98.8% and 76.9%, respectively.

Conclusion: NPD cysts can be accurately distinguished from the normal nasopalatine canal by measuring MLOO, AWE, and midAP diameter on CBCT images.

Keywords: CBCT; Discriminant functional analysis; Morphology; Nasopalatine canal; Nasopalatine duct cyst.

Fig. 1

Morphological parameters of the nasopalatine canal measured on reference CBCT section images. A, B. Measurements in a reference sagittal plane: APNO (in mm) - anteroposterior diameter of the nasal opening, APOO (in mm) - anteroposterior diameter of the oral opening, midAP (in mm) - mid-level anteroposterior diameter of the canal, L (in mm) – length of the canal, A (in degrees) – the angle between the canal axis and the nasal floor. C. AWE (in mm) – anterior wall expansion measured on the same sagittal image. D. Measurements in a reference coronal plane: MLNO (in mm) – mediolateral diameter of the nasal opening, minML (in mm) – minimum mediolateral diameter. E. Measurements in a reference axial plane: MLOO (in mm) – mediolateral diameter of the oral opening

Fig. 2

CBCT parameters measured in a patient with NPD cyst. (A) Sagittal plane measurements. Note the increase in size of the APOO and midAP caused by a cyst. (B) Coronal plane measurements. MinML was also increased due to the cyst. (C) Axial plane measurement