Three-Dimensional Morphometric Analysis of Cricoarytenoid Subluxation

Glottic Insufficiency in the Vertical Plane in Patients With Unknown-Source Unilateral Vocal Fold Hypomobility

OBJECTIVE

To observe the laryngeal CT and strobe laryngoscopy signs of unilateral vocal fold hypomobility (UVFHM) in patients with well-closed glottises in the horizontal plane.

METHODS

A retrospective analysis was performed on 18 subjects with well-closed glottises in the horizontal plane using strobe laryngoscopy, 9 patients diagnosed with unilateral vocal fold hypomobility with an unknown etiology were enrolled in the UVFHM group, and 9 healthy matched subjects with symmetrical bilateral vocal fold movement were enrolled in the control group. Vertical plane distances of bilateral vocal folds and three-dimensional structural parameters of vocal folds were measured through laryngeal CT. Glottic insufficiency in the vertical plane and reflux findings scores (RFS) were assessed under laryngeal CT and strobe laryngoscopy. Reflux symptom index (RSI) were collected. SPSS25.0 software was used for statistical analysis.

RESULTS

The height differences in vertical plane and thicknesses of bilateral vocal folds in the UVFHM group were larger than those in the control (P < 0.05), while the length, width and subglottic convergence angle of the vocal folds were not statistically significant between the two groups (P > 0.05). In the UVFHM group, laryngeal CT showed that 77.78% of patients (7/9) had glottic insufficiency in the vertical plane, with height differences ranging from 0.3 to 1.9 mm and a mean of 0.76mm. However, strobe laryngoscopy showed that 33.33% (3/9) had glottic insufficiency in the vertical plane. The proportion of patients with glottic insufficiency in vertical plane in the UVFHM group was significantly higher than that in the control group (P < 0.05). RSI and RFS scores of the UVFHM group were higher than those of the control group (P < 0.05).

CONCLUSION

Glottic insufficiency in the vertical plane often occurred in patients with UVFHM with an unknown cause of hoarseness, so the presence of glottic insufficiency in the vertical plane should be considered when hoarseness is detected by clinicians. Laryngeal dynamic CT can enhance the diagnostic rate compared to strobe laryngoscopy. Unexplained UVFHM patients have higher RSI and RFS compared to control subjects, warranting further research about the relationship between UVFHM and laryngopharyngeal reflux.

Analysis of Dysphagia and Cough Strength in Patients with Unilateral Vocal Fold Paralysis

The association between swallowing function and cough strength in patients with unilateral vocal fold paralysis (UVFP) is unknown. We evaluated the relationship between voluntary cough strength and dysphagia among patients with UVFP (UVFP group) by comparing their data with that of corresponding healthy participants (healthy control [HC] group) in a prospective observational study. From February 1st, 2018 to March 30th, 2019, we recruited patients with a voice disorder due to UVFP, who were referred to our university hospital. Patients with a history of laryngeal surgery, vagal nerve paralysis, or cardiac and respiratory failure were excluded. Descriptive and clinical data regarding swallowing, voice, and cough peak flow (CPF) were collected as a measure of cough strength. The UVFP group comprised six women and seven men (median age, 68.0 years), and the HC group comprised six women and eight men (median age 65.5 years). The groups differed significantly in the Eating Assessment Tool (EAT)-10 scores and CPF rates (P < 0.001). Among patients with UVFP, 84.6% had an abnormal EAT-10 score of ≥ 3. Additionally, 16.7% of the patients exhibited liquid aspiration with contrast medium on a videofluorographic swallowing study (VFSS). There was no correlation between the CPF values, EAT-10 scores, or the VFSS results. Therefore, patients with severe UVFP, whose condition had been fixed, had difficulties when swallowing (85% of cases), and some even presented with aspiration on VFSS (20% of cases), while receiving a regular diet.

Quantitative Measurement of the Three-dimensional Structure of the Vocal Folds and Its Application in Identifying the Type of Cricoarytenoid Joint Dislocation

OBJECTIVE

The objective of this study was to quantitatively measure the three-dimensional (3D) structure of the vocal folds in normal subjects and in patients with different types of cricoarytenoid dislocation. We will analyze differences in parameters between the groups and also determine if any morphologic parameters possess utility in distinguishing the type and the degree of cricoarytenoid dislocation.

STUDY DESIGN

This retrospective study was conducted using university hospital data.

METHODS

Subjects' larynges were scanned using dual-source computed tomography (CT). The normal subjects were divided into deep-inhalation and phonation groups, and patients with cricoarytenoid joint dislocation were divided into anterior-dislocation and posterior-dislocation groups. Membranous vocal fold length and width were measured directly on the thin-section CT images. Vocal fold and airway 3D models were constructed using Mimics software and used in combination to measure vocal fold thickness, subglottal convergence angle, and oblique angle of the vocal folds.

RESULTS

The phonation group displayed a greater vocal fold width, greater oblique angle, thinner vocal folds, and a smaller subglottal convergence angle than those of the deep-inhalation group (P < 0.05). The anterior-dislocation group displayed a smaller oblique angle and subglottal convergence angle than the posterior-dislocation group (P < 0.05).

CONCLUSIONS

The 3D structure of the vocal folds during deep inhalation and phonation can be accurately measured using dual-source CT and laryngeal 3D reconstruction. As the anterior-dislocation group yielded negative values for the oblique angle and the posterior-dislocation group yielded positive values, the oblique angle of the vocal folds may possess utility for distinguishing the type and for quantitatively determining the degree of cricoarytenoid dislocation.

MDCT in the assessment of laryngeal trauma: value of 2D multiplanar and 3D reconstructions

OBJECTIVE

The purpose of this study was to analyze fracture patterns and related effects of laryngeal trauma and to assess the value of 2D multiplanar reformation (MPR) and 3D reconstruction.

MATERIALS AND METHODS

Among 4222 consecutively registered trauma patients who underwent emergency MDCT, 38 patients had presented with laryngeal trauma. Axial, 2D MPR, 3D volume-rendered, and virtual endoscopic images were analyzed retrospectively by two blinded observers according to predefined criteria. Laryngeal fractures, soft-tissue injuries, and airway compromise were evaluated and correlated with clinical, endoscopic, surgical, and follow-up findings.

RESULTS

Fifty-nine fractures (37 thyroid, 13 cricoid, nine arytenoid) were present in 38 patients. They were isolated in 21 (55%) patients. The other 17 (45%) patients had additional injuries to the neck, face, brain, chest, or abdomen. Laryngeal fractures were bilateral in 31 (82%) patients and were associated with hyoid bone fractures in nine (24%) patients. Arytenoid luxation was present in eight cartilages. Axial imaging missed 7 of 59 (12%) laryngeal fractures, six of eight (75%) arytenoid luxations, and four of nine (44%) hyoid bone fractures. Additional 2D MPR imaging missed 5 of 59 (8%) laryngeal fractures, five of eight (62.5%) arytenoid luxations, and two of nine (22%) hyoid bone fractures, whereas 3D volume-rendered images depicted them all. Virtual endoscopy and 3D volume rendering added diagnostic accuracy with respect to the length, width, shape, and spatial orientation of fractures in 22 of 38 (58%) patients; arytenoid luxation in six of eight (75%) luxations; and the evaluation of airway narrowing in 19 of 38 (50%) patients. Three-dimensional volume rendering was not of additional value in evaluation of the cricoid cartilage.

CONCLUSION

The use of 2D MPR and 3D volume rendering with or without virtual endoscopy improved assessment of thyroid and hyoid bone fractures, arytenoid luxations, and laryngotracheal narrowing, providing helpful data for optimal management.

Imaging of laryngeal trauma

External laryngeal trauma is a rare but potentially life-threatening situation in the acutely injured patient. Trauma mechanism and magnitude, maximum focus of the applied force, and patient related factors, such as age and ossification of the laryngeal cartilages influence the spectrum of observed injuries. Their correct diagnosis and prompt management are paramount in order to avoid patient death or long-term impairment of breathing, swallowing and speaking. The current review provides a comprehensive approach to the radiologic interpretation of imaging studies performed in patients with suspected laryngeal injury. It describes the key anatomic structures that are relevant in laryngeal trauma and discusses the clinical role of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the acute emergency situation. The added value of two-dimensional multiplanar reconstructions (2D MPR), three-dimensional volume rendering (3D VR) and virtual endoscopy (VE) for the non-invasive evaluation of laryngeal injuries and for treatment planning is discussed. The clinical presentation, biomechanics of injury, diagnostic pitfalls and pearls, common and uncommon findings are reviewed with emphasis of fracture patterns, involvement of laryngeal joints, intra- and extralaryngeal soft tissue injuries, and complications seen in the acute emergency situation. The radiologic appearance of common and less common long-term sequelae, as well as treatment options are equally addressed.

Three-dimensional reconstruction of human vocal folds and standard laryngeal cartilages using computed tomography scan data

Three-dimensional (3D) computer models of the human larynx are useful tools for research and for eventual clinical applications. Recently, computed tomography (CT) scanning and magnetic resonance imaging (MRI) have been used to recreate realistic models of human larynx. In the present study, CT images were used to create computer models of vocal folds, vocal tract, and laryngeal cartilages, and the procedure to create solid models are explained in details. Vocal fold and vocal tract 3D models of healthy and postsurgery larynges during phonation and respiration were created and morphometric parameters were quantified. The laryngeal framework of eight patients was also reconstructed from CT scan images. For each cartilage, morphometric landmarks were measured on the basis of their importance for biomechanical modeling. A quantitative comparison was made between measured values from the reconstructions and those from human excised larynges in literature. The good agreement between these measurements supports the accuracy of CT scan-based 3D models. Generic standard models of the laryngeal framework were created using known features in modeling softwares. They were created based on the morphometric landmark dimensions previously defined, preserving all biomechanically important dimensions. These models are accessible, subject independent, easy to use for computational simulations, and make the comparisons between different studies possible.

High-force simulated intubation fails to dislocate cricoarytenoid joint in ex vivo human larynges

OBJECTIVES

We assessed the likelihood of arytenoid dislocation during intubation through the application of controlled force.

METHODS

Six cadaveric human larynges were mounted in an apparatus for simulating forcible collision with the arytenoid complexes. An endotracheal tube tip probe (ETTP) was used to push one arytenoid complex, and a non-slip probe (NSP) was tested on the other. Increasing pressure was applied until the probes either slipped or reached 5 kg of force. Dissection was then performed to assess the integrity of the cricoarytenoid ligament. The forces obtained by pushing an endotracheal tube against an electronic balance were measured to estimate the maximal possible intubating force.

RESULTS

None of the ETTP or NSP trials disrupted the cricoarytenoid joint ligaments, and the joint never appeared to be dislocated. The mean maximal forces were 1.8 kg for the ETTP (after which, slippage consistently occurred) and 4.7 kg for the NSP. The mean maximal forces from an endotracheal tube pushed against a scale were 1.5 kg (without stylet) and 4.6 kg (with stylet).

CONCLUSIONS

Arytenoid dislocation did not happen, and gross disruption of the joint capsule or ligament did not occur, even when the testing approximated the maximum force achievable under extreme conditions. Endotracheal tube insertion thus seems unlikely to cause arytenoid dislocation.