Velopharyngeal Structural and Functional Assessment of Speech in Young Children Using Dynamic Magnetic Resonance Imaging

Abstract

Objective: The purpose of this study was to demonstrate a novel method for examining the velopharyngeal mechanism using static and dynamic magnetic resonance imaging (MRI) at the sentence-level production in young children with normal anatomy. This study examined whether velopharyngeal events occurring in the midsagittal plane are correlated to muscle events occurring along the plane of velopharyngeal closure. Adenoid involvement in velopharyngeal function was also explored.

Methods: A high-resolution, T2-weighted turbo-spin-echo three-dimensional anatomical scan was used to acquire static velopharyngeal data and a fast-gradient echo fast low angle shot multishot spiral technique (15.8 frames per second) was used to acquire dynamic data on 11 children between 4 and 9 years old.

Results: Changes in velar knee height from rest to the bilabial /p/ production was strongly correlated with changes in the velar configuration (r = 0.680, P = .021) and levator muscle contraction (r = 0.703, P = .016). Velar configuration was highly correlated to levator muscle changes (r = 0.685, P = .020). Mean alpha angle during bilabial /p/ production was 176°, which demonstrated that subjects achieve velopharyngeal closure at or just below the palatal plane. Subjects with a larger adenoid pad used significantly less (r = -0.660, P = .027) levator muscle contraction compared with individuals with smaller adenoids.

Conclusions: This study demonstrates a potentially useful technique in dynamic MRI that does not rely on cyclic repetitions or sustained phonation. This study lends support to the clinical potential of dynamic MRI methods for cleft palate management.

Keywords: MRI; craniometry; imaging study; levator veli palatini muscle.

Figure 1:

Demonstration of measure for head flexion and extension. The vertical line passes along the anterior edge of the cervical vertebrae (C2-C3) and the oblique line connects the posterior tip of the spinous process of the first cervical vertebra with the tuberculum sella.

Figure 2:

Demonstration of the ABC angle obtained from midsagittal images at rest and during speech determined by intersecting points of posterior nasal spine (PNS), velar knee, and uvula. As the velar knee elevates the ABC angle decreases.

Figure 3:

Demonstration of the alpha angle obtained from midsagittal images determined by intersecting points of anterior nasal spine (ANS), posterior nasal spine (PNS), and velar knee (VN). Note as the velum elevates, the alpha angle becomes larger. An alpha angle of 180 degrees would indicate the velar knee was elevated to the level of palatal plane (ANS to PNS).

Figure 4:

The solid line (a) represents the image plane at which the oblique coronal image is obtained. The solid white box along the rest oblique coronal image (b) encompasses the levator muscle sling and is the field of view used in the dynamic oblique coronal images (c). The dotted white line (c) outlines the length of one levator muscle bundle and the arrow indicates the angle of origin. Note the dark muscle seen on the opposite side.

Fig 5:

Depth of the adenoid tissue was determined by measuring the nasopharyngeal margin of the adenoid tissue to the intersection of two reference lines—vertical line along the posterior pharyngeal wall and line through palatal plane (anterior nasal spine through posterior nasal spine). Image 5a presents a child with adenoid tissue and 5b presents a child with no apparent adenoid tissue.

Figure 6.

Oblique coronal and midsagittal images at rest across the two randomly selected females and two randomly selected males.

Figure 7:

Demonstration of the multiple viewpoints achieved using MRI to demonstrate sagittal (top left), axial (top right), oblique coronal (lower left), and an angled oblique coronal (lower right). As evident velar, velopharyngeal port (VP port), nasopharyngeal opening (NPO), cranial structures, hamulus, adenoids, musculus uvulae (MU), levator muscle (LVP), and palatoglossus (PG) can be visualized.