Morphology of the Musculus Uvulae In Vivo Using MRI and 3D Modeling Among Adults With Normal Anatomy and Preliminary Comparisons to Cleft Palate Anatomy

Abstract

Purpose: To investigate the musculus uvulae morphology in vivo in adults with normal velopharyngeal anatomy and to examine sex and race effects on the muscle morphology. We also sought to provide a preliminary comparison of musculus uvulae morphology in adults with normal velopharyngeal anatomy to adults with repaired cleft palate.

Methods: Three-dimensional magnetic resonance imaging data and Amira 5.5 Visualization Modeling software were used to evaluate the musculus uvulae in 70 participants without cleft palate and 6 participants with cleft palate. Muscle length, thickness, width, and volume were compared among participant groups.

Results: Analysis of covariance analysis did not yield statistically significant differences in musculus uvulae length, thickness, width, or volume by race or sex among participants without cleft palate when the effect of body size was accounted for. Two-sample t test revealed that the musculus uvulae in participants with repaired cleft palate is significantly shorter (P = .008, 13.65 mm vs 16.07 mm) and has less volume (P = .002, 51.08 mm³ vs 97.62 mm³) than participants without cleft palate.

Conclusion: In adults with normal velopharyngeal anatomy, the musculus uvulae is a cylindrical oblong-shaped muscle lying on the nasal surface of the soft palate, with its greatest bulk located just nasal to the levator veli palatini muscle sling. In participants with repaired cleft palate, the musculus uvulae is substantially reduced in volume. This diminished muscle bulk located just at the point where the palate contacts the posterior pharyngeal wall may contribute to velopharyngeal insufficiency in children with repaired cleft palate.

Keywords: 3-dimensional reconstruction; cleft palate; magnetic resonance imaging; morphology; musculus uvulae; race; sex.

Figure 1.

Display of measurements taken on 3D reconstruction of musculus uvulae obtained from MRI data. The sagittal view demonstrates (A) length of musculus uvulae (indicated by multiple arrows along muscle contour) and (B) thickness of musculus uvulae (indicated by double-headed arrow) measured at the greatest thickness. The oblique coronal/axial view shows (C) horizontal width of musculus uvulae (indicated by the bracket) measured at the thickness width.

Figure 2.

Comparisons of musculus uvulae length (a), thickness (b), width (c), and volume (d) among sex and race groups in adults with normal velopharyngeal anatomy. Height of the bars represents mean values for each respective measure, and the error bars represent interquartile range.

Figure 3.

Comparisons of musculus uvulae length (a), thickness (B), width (c), and volume (d) between participants with normal velopharyngeal anatomy and participants with repaired cleft palate, as well as comparisons of velum length (e) and velum thickness (f) as described in Perry et al. (2016). An asterisk (*) indicate statistically significant differences with p < 0.01.