Establishing a Clinical Protocol for Velopharyngeal MRI and Interpreting Imaging Findings

Abstract

Traditional imaging modalities used to assess velopharyngeal insufficiency (VPI) do not allow for direct visualization of underlying velopharyngeal (VP) structures and musculature which could impact surgical planning. This limitation can be overcome via structural magnetic resonance imaging (MRI), the only current imaging tool that provides direct visualization of salient VP structures. MRI has been used extensively in research; however, it has had limited clinical use. Factors that restrict clinical use of VP MRI include limited access to optimized VP MRI protocols and uncertainty regarding how to interpret VP MRI findings. The purpose of this paper is to outline a framework for establishing a novel VP MRI scan protocol and to detail the process of interpreting scans of the velopharynx at rest and during speech tasks. Additionally, this paper includes common scan parameters needed to allow for visualization of velopharynx and techniques for the elicitation of speech during scans.

Keywords: instrumental assessment; magnetic resonance imaging; secondary surgery; speech imaging; velopharyngeal insufficiency.

Figure 1.

Patient positioning in MRI scanner. Top left image shows incorrect localization to the nasion, resulting in an image focused on the brain and poor resolution of the velopharynx. By comparison, the top right image was obtained with the scanner localized to the nose tip, this creates a much higher quality view of the velopharyngeal region. The lower left image shows excessive head flexion, ideal neutral positioning (lower middle image), and excessive extension of the head (lower right image). Outlined in white (bottom middle) is an example of VP MRI field of view (FOV) to include the important VP anatomy, the full head, nose, and down to level of the chin included within the box.

Figure 2.

Establishing VP Imaging Planes. The top row shows how to set the mid-sagittal plane off of the localization scans. Image A shows a midsagittal slice and the location of the coronal slice (shown in red line in A and then viewed in image B. The sagittal slices should span the width of the pharynx as seen in image C. The bottom row shows how to set the oblique coronal using the location of the spheno-occiptal synchondrosis (visualized in images D and E). The FOV should be large enough to cover the region noted below in image F and should span from the posterior edge of bony palate through the entire velum.

Figure 3.

Larger image on left shows the normal LVP anatomy in a non-cleft individual in comparison to 4 cases of patients with VPI at rest (top row) and during sustained /i/ (bottom row). Variations in the LVP are evident across patients including a dehiscence of the LVP at the velar midline (patients A, B, and C), thin LVP (patient D), notching in the nasal velar surface (patient B), and in all cases a gap in the VP port.

Figure 4.

Demonstration of a midsagittal image (top left figure highlights in red box the region of interest for larger images) showing a case of non-cleft anatomy (image A) and distance from the posterior nasal spine (arrow) compared to the location of the levator insertion point into the body of the velum (encircled region). In contrast, image B highlights a child with repaired cleft palate and VPI who demonstrates a levator muscle that is substantially closer to the posterior hard palate, which results in an anteriorly positioned velar knee during phonation as seen in image C.