Aortic arch compliance and idiopathic unilateral vocal fold paralysis

Immediate effect of recurrent laryngeal nerve stimulation in patients with idiopathic unilateral vocal fold paralysis

BACKGROUND

There is a lack of effective treatment for idiopathic unilateral vocal fold paralysis (IUVFP). A better phonation was reported by patients after laryngeal nerve stimulation during our clinical examination.

OBJECTIVES

This study aims to investigate immediate effect of recurrent laryngeal nerve (RLN) stimulation on phonation in patients with IUVFP.

MATERIAL AND METHODS

Sixty-two patients with clinically identified IUVFP underwent RLN stimulation with needle electrodes. Laryngoscopy, acoustic analysis, and voice perception assessment were performed for quantitative comparison of vocal function and voice quality before and after the intervention.

RESULTS

Laryngoscopic images showed a larger motion range of the paralyzed vocal fold (p < .01) and better glottal closure (p < .01) after RLN stimulation. Acoustic analysis revealed that the dysphonia severity index increased significantly (p < .01) while the jitter and shimmer decreased after the intervention (p < .05). According to perceptual evaluation, RLN stimulation significantly increased RBH grades in patients with IUVFP (p < .01). Furthermore, the improvement in voice perception had a moderate positive correlation with the decrease in the glottal closure.

CONCLUSIONS AND SIGNIFICANCE

This study shows a short-term improvement of phonation in IUVFP patients after RLN stimulation, which provides proof-of-concept for trialing a controlled delivery of RLN stimulation and assessing durability of any observed responses.

Computed Tomography Measurements in Assessment of Idiopathic Vocal Fold Paralysis

OBJECTIVE

Our study aimed to both identify the incidence and clinical presentation of patients presenting with idiopathic vocal fold paralysis (IVFP). Secondarily we aimed to assess the radiographic findings of computed tomography (CT) studies along the course of the vagus and recurrent laryngeal nerves (RLN), specifically measuring for potential areas of compression at the skull base and mediastinum. We hypothesized that a proportion of patients diagnosed with IVFP would have significant differences in measurements when compared to age-gender matched controls on CT imaging.

STUDY DESIGN

Institutional review board approved retrospective cohort study METHODS: We assessed patients presenting to a tertiary voice care center between 2003 and 2019 with diagnosis of vocal fold paralysis. Data collected includes demographics, clinical exam findings, and CT measurements including dimensions at bilateral jugular foramen, aortopulmonary (AP) window and surrounding vascular structures. Statistical analysis was then performed using Pearson χ², and Mann Whitney U tests to determine differences variables of interest.

RESULTS

A total of 606 patients were reviewed. Of these patients 60 (9.9%) patients were determined to have IVFP. Left-sided VFP was seen more commonly in 78.3% (N = 47) of idiopathic patients. Our IVFP group had an overall higher incidence of cardiovascular disease [OR = 3.378, 95%CI 1.907-5.941, P < 0.001] compared to those with identified causes for paralysis. Specifically, IVFP patients showed a higher incidence of combined cardiovascular co-morbidities (P < 0.001), mitral valve stenosis (P = 0.007), pulmonary hypertension (P < 0.0001) and congestive heart failure (P < 0.001). When evaluating CT imaging, the AP window was mentioned in only 2 (3.3%) of our idiopathic patients CT reports. The IVFP cohort had a lower median AP window volume (P = 0.020) when compared to age-gender matched controls. This significantly smaller AP window volume was also seen when only left sided IVFP compared to both right-sided paralysis (P < 0.001) and age matched control patients (P < 0.001).

CONCLUSION

The significance of cardiovascular comorbidities combined with findings of statistically narrowed AP window may help provide an explanation of a subset of patients diagnosed with IVFP.

Extracellular matrix deformations of the porcine recurrent laryngeal nerve in response to hydrostatic pressure

Damage to the recurrent laryngeal nerve (RLN) caused by supraphysiological compression or tension imposed by adjacent tissue structures, such as the aorta, may contribute to onset of idiopathic unilateral vocal fold paralysis (iUVP) resulting in difficulty speaking, breathing, and swallowing. We previously demonstrated in adolescent pigs that the right RLN epineurium exhibits uniform composition of adipose tissue, with larger quantities along its length within the neck region in contrast to the left RLN that shows greater collagen composition in the thoracic region and greater quantities of adipose tissue in the neck region. In contrast, the epineurium in piglets was primarily composed of collagen tissue that remained uniform along the length of the left and right RLNs. Tensile testing of the left and right RLN in piglets and pigs showed associated differences in strain by RLN side and segment by age. The goal of this study was to investigate how external hydrostatic compression of the RLN affects the nerve's connective tissue and microstructure. RLN segments were harvested from the distal (cervical/neck) regions and proximal (subclavian for the right RLN, thoracic for the left RLN) regions from eight adolescent pigs and nine piglets. RLN segments were isolated and assessed under fluid compression to test hypotheses regarding epineurium composition and response to applied forces. Second harmonic generation (SHG) imaging of epineurial collagen was conducted at 0, 40, and 80 mmHg of compression. The cartesian strain tensor, principal strain (Eps1), and principal direction of the RLN collagen fibers were determined at each pressure step. Significantly larger values of the 1st principal strain occurred in the proximal segments of the pig left RLN when compared to the same segment in piglets (p = 0.001, pig = 0.0287 [IQR = 0.0161 - 0.0428], piglet = 0.0061 [IQR = 0.0033 - 0.0156]). Additionally, the median transverse strain Eyy) for the second pressure increment was larger in the right proximal segment of pigs compared to piglets (p < 0.001, pig = 0.0122 [IQR = 0.0033 - 0.0171], piglet = 0.0013 [IQR = 0.00001 - 0.0028]). Eyy values were significantly larger in the right proximal RLN versus the left proximal RLNs in pigs but not in piglets (p < 0.001). In contrast to piglets, histological analysis of pig RLN demonstrated increased axial alignment of epineurial and endoneurial collagen in response to compressive pressure. These findings support the hypothesis that the biomechanical response of the RLN to compressive pressure changed from being similar to being different between the right and left RLNs during development in the porcine model. Further investigation of these findings associated with age-related onset of idiopathic UVP may illuminate underlying etiologic mechanisms. STATEMENT OF SIGNIFICANCE: Damage to the recurrent laryngeal nerve (RLN) caused by compression imposed by the aorta may contribute to the onset of left-sided idiopathic unilateral vocal fold paralysis resulting in difficulty speaking, breathing, and swallowing. The goal of this study was to investigate how compression affects the connective tissue and microstructure of the RLN. We quantified the pressure induced deformation of the RLN using multiphoton imaging as a function of both location (proximal versus distal) and age (piglets, adolescent pigs). Our results demonstrate that the biomechanical response of the RLN to compression changes in the right versus left RLN throughout development, providing further evidence that the the left RLN is exposed to increasing dynamic loads with age.

Development of an FEA framework for analysis of subject-specific aortic compliance based on 4D flow MRI

This paper presents a subject-specific in-silico framework in which we uncover the relationship between the spatially varying constituents of the aorta and the non-linear compliance of the vessel during the cardiac cycle uncovered through our MRI investigations. A microstructurally motivated constitutive model is developed, and simulations reveal that internal vessel contractility, due to pre-stretched elastin and actively generated smooth muscle cell stress, must be incorporated, along with collagen strain stiffening, in order to accurately predict the non-linear pressure-area relationship observed in-vivo. Modelling of elastin and smooth muscle cell contractility allows for the identification of the reference vessel configuration at zero-lumen pressure, in addition to accurately predicting high- and low-compliance regimes under a physiological range of pressures. This modelling approach is also shown to capture the key features of elastin digestion and SMC activation experiments. The volume fractions of the constituent components of the aortic material model were computed so that the in-silico pressure-area curves accurately predict the corresponding MRI data at each location. Simulations reveal that collagen and smooth muscle volume fractions increase distally, while elastin volume fraction decreases distally, consistent with reported histological data. Furthermore, the strain at which collagen transitions from low to high stiffness is lower in the abdominal aorta, again supporting the histological finding that collagen waviness is lower distally. The analyses presented in this paper provide new insights into the heterogeneous structure-function relationship that underlies aortic biomechanics. Furthermore, this subject-specific MRI/FEA methodology provides a foundation for personalised in-silico clinical analysis and tailored aortic device development. STATEMENT OF SIGNIFICANCE: This study provides a significant advance in in-silico medicine by capturing the structure/function relationship of the subject-specific human aorta presented in our previous MRI analyses. A physiologically based aortic constitutive model is developed, and simulations reveal that internal vessel contractility must be incorporated, along with collagen strain stiffening, to accurately predict the in-vivo non-linear pressure-area relationship. Furthermore, this is the first subject-specific model to predict spatial variation in the volume fractions of aortic wall constituents. Previous studies perform phenomenological hyperelastic curve fits to medical imaging data and ignore the prestress contribution of elastin, collagen, and SMCs and the associated zero-pressure reference state of the vessel. This novel MRI/FEA framework can be used as an in-silico diagnostic tool for the early stage detection of aortic pathologies.

Vocal Fold Mobility Impairment After Cardiovascular Surgery: Incidence, Risk Factors, and Sequela

BACKGROUND

We aimed to determine the incidence and contributing risk factors of vocal fold mobility impairment (VFMI) in postoperative cardiovascular patients and evaluate the impact of VFMI on health-related outcomes.

METHODS

This single-site prospective study enrolled adults undergoing sternotomy or thoracotomy procedures who underwent a fiberoptic laryngoscopy examination within 72 hours of extubation. Potential demographic and surgical risk factors and health-related outcomes were collected. A blinded laryngologist assessed VFMI and mucosal injury. Descriptives, univariate and multivariable regression analyses with odds ratios (OR) were performed.

RESULTS

Of 185 eligible examinations, VFMI was confirmed in 25% of patients (7 complete, 39 partial VFMI) with left-sided involvement in 83% of cases. Laryngeal mucosal injury included granuloma (38%), posterior cricoid hypertrophy (37%), edema (29%), bruising (23%), and hemorrhage (9%). Independent risk factors for complete VFMI were aortic arch procedure (odds ratio 6.1), body mass index less than 25 (OR: 7.2), and African-American or Hispanic race (OR: 6.0). Patients with two or more identified risk factors had a 33.0 increased odds of complete VFMI compared with patients not having two or more risk factors. Compared with patients having normal vocal fold motion, patients with complete VFMI had a 2.7 increased odds of pneumonia, 5.7 higher odds of reintubation, a 7.3 times higher odds of death, and increased length of hospital stay and cost of care (P < .05).

CONCLUSIONS

Interdisciplinary postoperative care and laryngoscopy examination are recommended for high-risk patients to facilitate early detection and improve patient outcomes.

Idiopathic Unilateral Vocal Fold Paralysis in Older Patients: Characteristics in the Disease Course and Implication of Computed Tomography for Evaluation of Etiology

OBJECTIVES

This study aimed to compare the characteristics of idiopathic unilateral vocal fold paralysis (IUVFP) in elderly versus younger patients, including the diagnostic yield of computed tomography (CT) scans for identifying the structural causes of IUVFP.

METHODS

We retrospectively analyzed medical records of the patients initially diagnosed with IUVFP in a single referral tertiary hospital. We compared patients' baseline characteristics, initial symptoms, laryngoscopic findings, and prevalence of structural causes on CT scans with respect to age (younger, <65 years vs older, ⩾65 years).

RESULTS

One hundred forty-two patients were enrolled (90 younger, 52 older). Evident structural causes were more frequently found on CT in older patients than younger patients (40.4% vs 22.2%, P = .034). Among truly idiopathic cases (70 younger, 31 older), recovered vocal fold mobility was identified in 48.6% younger and 41.9% older patients ( P = .666). There was no statistically significant difference in the characteristics between unrecovered and recovered subjects of the older patients with true IUVFP (all P > .05).

CONCLUSIONS

The CT scans provided significantly higher diagnostic yields in older patients than younger patients. The degrees of symptoms and complications and likelihood of natural recovery did not significantly differ between younger and older patients with IUVFP.

Association between Upper Respiratory Infection and Idiopathic Unilateral Vocal Fold Paralysis

INTRODUCTION

Unilateral vocal fold paralysis (UVFP) without an identifiable cause is termed idiopathic unilateral vocal fold paralysis (IUVFP). Some authors have postulated that select cases of IUVFP have a viral etiology, but the causality has not been established. We set out to review institutional cases of IUVFP and determine if there is a correlation between upper respiratory infection symptoms and presentation of IUVFP.

METHODS

Cases of IUVFP were reviewed over a 10-year period (2002-2012). The history was investigated to review presenting symptoms. We specifically reviewed for symptoms of upper respiratory infection at the onset of UVFP and tallied the frequency. Symptoms included sore throat, laryngitis, cough, influenza, bronchitis, pneumonia, otalgia, and sinusitis. The seasonal onset (if possible) was determined based on the history provided from the initial consultation.

STUDY DESIGN

Case series.

RESULTS

Overall, 107 patients presented with IUVFP; 35.5% of patients reported symptoms of upper respiratory infection at the onset of UVFP. Among these individuals, pharyngitis/laryngitis was the most common presenting symptom; 34.2% reported cough. In total, 40.0% of patients with IUVFP reported an onset of symptoms between December and February.

CONCLUSIONS

This study suggests that symptoms of upper respiratory infection frequently occur with the presentation of IUVFP. The onset of symptoms tended to occur between December and February. The mechanism of viral-mediated UVFP has not been established. Future studies to explore this pathophysiology are needed.