Semon's law revisited: an electromyographic analysis of laryngeal synkinesis

Electromyographic Evaluation of Vocal Folds in Patients With Laryngeal Paralysis Referred for Injection Laryngoplasty

BACKGROUND

According to the literature, almost 80% of the patients diagnosed with permanent unilateral laryngeal paralysis experience vocal disability. Laryngeal electromyography (LEMG) provides information on the characteristics and progression of the disease process, allowing for optimal treatment. The aim of this study was to evaluate LEMG recordings in patients with unilateral vocal fold (VF) immobility referred for injection laryngoplasty (IL).

MATERIAL AND METHODS

17 patients with unilateral laryngeal immobilisation as an iatrogenic complication after neck surgery. The patients were referred for IL surgery due to glottic insufficiency. All patients underwent a preoperative otolaryngologic-phoniatric evaluation with perceptual and acoustic voice assessment and LEMG.

RESULTS

Patients with unilateral VF immobilisation referred for injection laryngoplasty for glottal insufficiency show significant differences on LEMG between the mobile and immobile folds. In these patients, electromyography (EMG) features of the thyroarytenoid (TA) muscle correlate with the severity of breathiness in the voice and pathological variation in the fundamental frequency. Despite the lack of mobility and features of VF atrophy, only 12% meet the electromyographic criterion for vocal fold paralysis. The immobile VF has a poorer recording from the TA muscle, the more material needs to be injected to surgically model the glottis during IL.

CONCLUSIONS

This study demonstrated that LEMG is a valuable criterion for qualifying patients for injection laryngoplasty in unilateral vocal fold paralysis.

The Management in Patients With Bilateral Vocal Fold Immobility: 15 Years' Experience at a Tertiary Centre

OBJECTIVE

In order to correct the varying vocal fold positions to meet the various clinical requirements in patients with bilateral vocal fold immobility, we present pertinent surgical methods to treat them.

MATERIALS AND METHODS

From 2005 to 2020, 115 patients diagnosed with bilateral vocal fold immobility were addressed for ventilation in 89 patients and for phonation in 26 patients. In the ventilation surgery group, all the neurogenic subjects received mere suture lateralization (SL) procedures and the mechanical ones underwent arytenoid release (AR) plus SL procedures if the cricoarytenoid joint fixation (CAJF) could be confirmed before operation. In the phonation group, neurogenic subjects received nonsurgical treatment and the mechanical ones underwent AR plus arytenoid adduction (AA) procedure. The decannulation rate and respiratory comfort rate for each subgroup will be calculated and the phonatory tests were conducted.

RESULTS

In the ventilation group, 55% (49/89) of subjects received related surgeries. Mere SL offered 40 successful decannulation or respiratory comfort in 42 neurogenic subjects (95.2%). The single episode rate was high as 95%. An AR plus SL procedure also obtained 100% of decannulation or respiratory comfort with a single episode of surgical procedure if the CAJF could be confirmed preoperatively. In the phonation group, 15% (4/26) of subjects received appropriate surgeries. Single AR plus AA procedures also led to 100% (4/4) of the appropriate candidates serviceable sound.

CONCLUSION

SL procedure keeping intact laryngeal mucosa usually offered permanent glottis enlarging effect or decannulation with a single episode of procedure. The use of arytenoid release for CAJF has led to remarkable advances in the ultimate surgical outcomes of both the ventilation and phonation in terms of decreasing revision surgeries.

LEVELS OF EVIDENCE

level 4.

The Causes and Laryngeal Electromyography Characteristics of Unilateral Vocal Fold Paralysis

OBJECTIVE

To investigate the causes and laryngeal electromyography (LEMG) characteristics of unilateral vocal fold paralysis (UVFP).

METHODS

We retrospectively analyzed the history and LEMG of 337 patients with unilateral vocal fold immobility. The etiology was reviewed and the characteristics of LEMG (including spontaneous potential, recruitment potential, evoked potential, synkinesia, and et al.) were analyzed.

RESULTS

The causes included injury (177 cases, 52.5%), idiopathic causes (72 cases, 21.4%), infection (61 cases, 18.1%), tumor and compressive factors (27 cases, 8.0%). Among the injury group, 161 cases were caused by surgery (111 cases of thyroid surgery), and 16 cases were caused by trauma. LEMG showed that complete nerve injury was present in 72.9% of the injury group, 66.7% of the tumors or compressive factors group, 49.2% of the infection group, and 44.4% of the idiopathic group. Of the 337 patients, 136 patients (40.4%) had synkinesia in the posterior cricoarytenoid muscles, and only two of these patients also had synkinesia in the thyroarytenoid muscles. The proportion of complete recurrent laryngeal nerve (RLN) injury in patients with synkinesia was higher than that of patients without synkinesia.

CONCLUSION

The main cause of vocal fold paralysis is neck surgery, most commonly thyroid surgery. Patients with different causes of paralysis had different severities of RLN injury. LEMG showed that surgery or trauma accounted for the highest proportion of complete nerve injury. Patients with severe RLN injury were more prone to synkinesia, and the posterior cricoarytenoid muscles were more likely to have synkinesia than the thyroarytenoid muscles.

Laryngeal Nerves and Voice Change in Thyroid Surgery

The low incidence of injury to the recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN) quoted in the literature is derived from expert series. The exact incidence of nerve injury of a thyroid surgeon will be revealed only if pre-operative and post-operative laryngoscopy is becoming routine practice. It is found that the injury rates are increased with routine post-operative laryngoscopy. Subjective voice change occurred in one third of patients all whom had normal vocal cord motion. Therefore, it is important to take written informed consent for voice change in addition to identification of both nerves and documenting it.

Hoarseness

Hoarseness is a common problem, typically of transient nature. When hoarseness does not resolve, or when it is associated with concerning symptoms, it is important to consider a wide differential and refer to an otolaryngologist. This article discusses the physiology of the voice and possible causes of dysphonia, and explores when it warrants further work-up by ENT. A discussion of diagnostic techniques and the myriad of tools to treat hoarseness follows. Additionally, the role of reflux in dysphonia is examined with a critical eye to aid in accurate assessment of the patient's complaint.

[Neurolaryngology]

Neurological and neurophysiological knowledge of neuromuscular diseases is combined in neurolaryngology with experience from laryngology. Laryngeal electromyography (LEMG) is the most important diagnostic and prognostic tool in neurolaryngology. It can be combined with diagnostic electrostimulation. Interest in LEMG today extends beyond the thyroarytenoid muscle to all accessible laryngeal muscles. LEMG should be performed and interpreted according to a standardized protocol. Main applications of LEMG are confirmation, topodiagnostic and prognostic assessment of vocal fold paralysis. It is possible to differentiate fresh from old recurrent laryngeal nerve lesions as well as mechanical vocal fold fixations from paralysis. Needle guidance for botulinum toxin injections in spasmodic dysphonia and for augmentation laryngoplasty can be supported by LEMG, but also by laryngeal ultrasound. The timing of therapy for temporary and permanent augmentations, thyroplasty and reinnervation surgery may be better defined with experience from neurolaryngology. The use of diagnostic neurostimulation can reveal any remaining active movement potential of a vocal fold and thus help identify candidates for future laryngeal pacemaker treatments. Other topics in neurolaryngology include spasmodic dysphonia and underlying neurological diseases such as stroke, central vocal fold paralysis, essential tremor and Parkinson's disease. Laryngoscopic, clinical and LEMG characteristics of these diseases are presented.

Quantitative laryngeal electromyography (LEMG) in unilateral vocal fold paralysis: Developing normative values using the opposite normal mobile vocal fold

OBJECTIVE

Laryngeal electromyography (LEMG) is used to confirm neuropathy; traditionally, it is evaluated qualitatively. This study aimed to develop normative values for the thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex by determining the mean turns (MT) and mean amplitudes (MA) using the opposite normal mobile vocal fold in unilateral vocal fold paralysis (VFP). This study also compared the MT and MA of the paralyzed vocal fold with that of the normal side and analyzed their correlations.

METHODS

This is a cross-sectional study in which 77 patients (18 males, 59 females, mean age of 48) with unilateral VFP with an opposite normal mobile vocal fold underwent LEMG with a standardized protocol. Koufman gradings and MT and MA were used for the qualitative and quantitative evaluations. Mann-Whitney U test was performed to compare the median of the turns and amplitudes between the opposite normal mobile vocal fold and the paralyzed side. A linear-scale graphical "cloud" of the normal TA-LCA muscle complex was generated using logarithmic regression analysis. The qualitative and quantitative parameters were analyzed using multiple analysis of variance and Kruskall-Wallis test. Post-hoc analysis was performed to further determine the differences of the significance between both parameters. The correlation between the qualitative and quantitative parameters was analyzed using Spearman correlation.

RESULTS

The MT and MA were significantly higher for the normal TA-LCA muscle complex than the paralyzed side (582 vs. 336; 412 vs. 296, respectively) and the median of the turns and amplitudes were significantly lower in the paralyzed side with p-values <0.001. A significant difference was observed between the Koufman grading and the combination of MT and MA [F (8,144) = 73.254] and between the Koufman grading and MT and MA individually [H (4, 72) = 18.3 and H (4, 72) =33.4], in which both had p-values <0.001. A moderate negative linear relationship was seen between the Koufman grading and MT and MA. On further analysis, it was revealed that only certain pairs of Koufman grading were statistical significant.

CONCLUSIONS

This study was the first to present the quantitative normative values and "cloud" of the TA-LCA muscle complex using the opposite normal mobile vocal fold in patients with unilateral VFP in which it is comparable to healthy controls. We concluded that quantitative LEMG supports the qualitative Koufman grading method however it cannot be used independently to determine the severity of neuropathy.

Optimal Arytenoid Position in Laryngeal Framework Surgery: An Anatomic Human Larynx Study

OBJECTIVES

The purpose of this study was to better understand the effects of stitch placement on arytenoid medialization by measuring normative cricoarytenoid joint anatomy and changes in arytenoid position when varying arytenopexy stitch configuration.

METHODS

This adult human larynx study was done in two parts. First, measurements of the cricoid and arytenoid cartilage anatomy relevant to cricoarytenoid joint function were made in 45 preserved larynges (26 male (M), 19 female (F)) using digital calipers. Second, the arytenoids of six fresh larynges ( three M, three F) were sutured to the cricoid using various arytenopexy-stitch placements ranging from inferior-lateral to superior-medial, and the resulting arytenoid positions were compared by measuring medial displacement of the arytenoid body and change in glottal configuration from macro still images using Image J. Paired t-tests were used to compare the results.

RESULTS

Cartilage and joint facet dimensions showed differences between males (M) and females (F). Cricoid facet lengths averaged 9.3 mm (M) and 7.1 mm (F), and widths averaged 4.9 mm (M) and 4.0 mm (F). The arytenoid facet widths averaged 10.5 mm (M) and 9.7 mm (F). Average distances between cricoid facets were 11.8 mm for both males and females. Securing the arytenoid superior-medially on the cricoid facet produced more medialization (2.2 mm vs 1.0 mm, P < .001) and better glottic aperture configuration (9.5° vs 2.7°, P < .001) than securing the arytenoid inferior-laterally on the facet.

CONCLUSIONS

Anatomic consistency in cricoarytenoid anatomy provides reliable surgical landmarks for ideal placement of an arytenopexy suture to optimally reposition the arytenoid cartilage. Optimal arytenoid medialization can be accurately reproduced with an arytenopexy-suture that is placed superior-medially on the cricoid facet.

LEVEL OF EVIDENCE

NA Laryngoscope, 2021.

Diagnostic limitation of laryngostroboscopy in comparison to laryngeal electromyography in synkinesis in unilateral vocal fold paralysis

Purpose

In clinical practice, laryngo(strobo)scopy (LS) is still mainly used for diagnostics and management of unilateral vocal fold paralysis (UFVP), although only laryngeal electromyography (LEMG) can provide information on causes of vocal fold immobility, especially on possible synkinetic reinnervation after recurrent laryngeal nerve (RLN) injury. The goal of this retrospective study was the evaluation whether signs of synkinetic reinnervation in LS can be objectified in comparison to LEMG data.

Methods

Between 1/2015 and 2/2018, 50 patients with laryngostroboscopically suspected UVFP received routine LEMG examination. The LEMG findings were retrospectively compared with LS findings. The LEMG data analysis focused on the diagnosis of synkinetic reinnervation of the TA/LCA and/or PCA. The digital LS recordings were retrospectively re-evaluated by phoniatricians considering 22 selected laryngostroboscopic parameters.

Results

LEMG revealed synkinesis in 23 (46%) and absence of synkinesis in 27 (54%) patients. None of the 22 parameters showed significant association between patients with synkinetic reinnervation and LS findings. The only laryngostroboscopic parameter that was significantly associated with a silent LEMG signal compared to single fiber activity in LEMG was a length difference on the side of the UVFP (p-value 0.0001; OR 14.5 (95% CI 3.047–66.81; Sensitivity 0.5; Specificity 0.9355).

Conclusion

Our findings show that synkinesis cannot be diagnosed using only LS. This study underlines the importance of LEMG in clinical routine for detection of laryngeal synkinesis in patients with UVFP before any further therapeutic steps are initiated to avoid later therapy failure.

Crumley's Classification of Laryngeal Synkinesis: A Comparison of Laryngoscopy and Electromyography

OBJECTIVES/HYPOTHESIS

Applying the principles of misdirected nerve regeneration to the larynx, Roger Crumley in 1989 coined the term laryngeal synkinesis (LS) which he later (2000) classified into 4 types (type I - good voice, type II - involuntary twitches and poor voice, type III - adduction during inspiration, type IV - abduction during phonation). Neurophysiological data were not available for all LS patients at that time. The current study was undertaken to utilize and test the Crumley classification for a clinical interrater comparison and, secondly, compare predicted with actual laryngeal electromyography (LEMG) results.

STUDY DESIGN

Descriptive study.

METHODS

Laryngoscopic and LEMG data of patients with unilateral vocal fold paralysis (VFP) of 6 months duration or longer were combined for retrospective evaluation. Forty-five data sets were available for laryngoscopic classification by two local laryngologists and by Roger Crumley. Twenty-three data sets with complete thyroarytenoid (TA) and posterior cricoarytenoid (PCA) - EMG data were used to compare predicted with actual LEMG results.

RESULTS

Local laryngologists were able to classify 24 of 45, Crumley 30 of 45 cases into one of the 4 synkinesis types. There was substantial agreement between examiners (Cohens Kappa 0.66 [P < .001]). Comparison of predicted and actual LEMG data showed only moderate agreement. EMG sykinesis rates were lower in TA than in PCA and highest in Crumley type I cases.

CONCLUSION

The Crumley classification is helpful in describing and understanding synkinesis. It does not always correlate predictably with actual LEMG data. A complete LEMG mapping of all intrinsic muscles may improve understanding of chronic VFP.

LEVEL OF EVIDENCE

4. Laryngoscope, 131:E1605-E1610, 2021.

PCA Atrophy and Synkinesis as the Main Factors for Persistent Vocal Fold Immobility in RLN Paralysis

OBJECTIVES/HYPOTHESIS

An immobile vocal fold due to recurrent laryngeal nerve (RLN) injury usually shows no gross signs of atrophy and lies near the midline. In 1881, Felix Semon proposed that this phenomenon was due to a selective injury of nerve fibers supplying the posterior cricoarytenoid muscle (PCA) and supported this with postmortem proof of selective PCA atrophy. In recent decades, evidence has emerged that the RLN regenerates after injury but does not always result in useful motion of the vocal folds. It has been proposed that this is caused by laryngeal synkinesis. Laryngeal synkinesis describes a random distribution of regenerated nerve fibers to opposing vocal fold muscles. This study was conducted to clarify the relative contribution of these two potential pathomechanisms in our patient population.

STUDY DESIGN

Retrospective case analysis.

METHODS

Retrospective analysis of laryngeal EMG results from cases with RLN paralysis of at least 6 months duration seen at our neurolaryngology clinic.

RESULTS

Out of 118 PCA EMGs, there was not a single normal or near-normal tracing, whilst 33.3% of TA EMGs indicated normal or near normal innervation. PCA EMGs showed signs of persistent high-grade partial denervation (41.5%) as a sign of atrophy, moderate or strong synkinesis (21.2%), or a combination of both (37.3%).

CONCLUSIONS

In chronic RLN paralysis the intrinsic laryngeal muscles are affected to different extents either by atrophy or synkinesis or a combination of both. The PCA is always affected. The lesser damage to TA innervation explains the commonly seen maintenance of vocal fold muscle bulk.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1244-E1248, 2021.

Inter-rater reliability of seven neurolaryngologists in laryngeal EMG signal interpretation

Purpose

Laryngeal electromyography (LEMG) has been considered as gold standard in diagnostics of vocal fold movement impairment, but is still not commonly implemented in clinical routine. Since the signal interpretation of LEMG signals (LEMGs) is often a subjective and semi-quantitative matter, the goal of this study was to evaluate the inter-rater reliability of neurolaryngologists on LEMGs of volitional muscle activity.

Methods

For this study, 52 representative LEMGs of 371 LEMG datasets were selected from a multicenter registry for a blinded evaluation by 7 experienced members of the neurolaryngology working group of the European Laryngological Society (ELS). For the measurement of the observer agreement between two raters, Cohen’s Kappa statistic was calculated. For the interpretation of agreements of diagnoses among the seven examiners, we used the Fleiss’ Kappa statistic.

Result

When focusing on the categories “no activity”, “single fiber pattern”, and “strongly decreased recruitment pattern”, the inter-rater agreement varied from Cohen’s Kappa values between 0.48 and 0.84, indicating moderate to near-perfect agreement between the rater pairs. Calculating with Fleiss’ Kappa, a value of 0.61 showed good agreement among the seven raters. For the rating categories, the Fleiss’ Kappa value ranged from 0.52 to 0.74, which also showed a good agreement.

Conclusion

A good inter-rater agreement between the participating neurolaryngologists was achieved in the interpretation of LEMGs. More instructional courses should be offered to broadly implement LEMG as a reliable diagnostic tool in evaluating vocal fold movement disorders in clinical routine and to develop future algorithms for therapy and computer-assisted examination.

The impact of cricothyroid involvement on adductor recovery in unilateral vocal fold paralysis

OBJECTIVES/HYPOTHESIS

Wide variation in postinjury functional recovery is a hallmark of unilateral vocal fold paralysis (UVFP), ranging from zero to full recovery. The present study examined the impact of cricothyroid (CT) muscle involvement on recovery using quantitative laryngeal electromyography (LEMG) of the thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex at multiple times postinjury.

STUDY DESIGN

Prospective cohort study in a medical center.

METHODS

Eighty-one patients with UVFP (37 males and 44 females) received an initial assessment of quantitative LEMG, stroboscope, acoustic voice analysis and 36-Item Short Form Survey quality-of-life questionnaire at 3 to 6 months after UVFP onset and a follow-up assessment at 12 months after UVFP onset.

RESULTS

The initial and follow-up assessments were performed at 4.3 ± 1.9 and 12.5 ± 1.3 months after UVFP onset, respectively. The peak turn frequency of the TA-LCA muscle complex on the lesion side was improved at the follow-up (470 ± 294 Hz) compared with the initial assessment (300 ± 204 Hz) (P < .001). Patients were also divided into two groups with (n = 27) and without (n = 54) CT involvement, respectively. TA-LCA muscle complex turn frequency improved in patients without CT involvement (from 277 ± 198 to 511 ± 301 Hz; P < .001), but not in those with CT involvement (from 345 ± 211 to 386 ± 265 Hz; P = .46). Seventy-one of all patients received early intervention with intracordal hyaluronate injection, showing similar therapeutic effects in those with and without CT involvement.

CONCLUSIONS

Acute UVFP with combined TA-LCA muscle complex and CT muscle involvement has a poor prognosis, with poorer recovery of TA-LCA muscle complex recruitment. Early interventions should be considered in patients with UVFP with CT involvement.

LEVEL OF EVIDENCE

2 Laryngoscope, 130:139-145, 2020.

Spasmodic Dysphonia: A Review. Part 1: Pathogenic Factors

Objective The purpose of this review is to describe the recent advances in identifying possible factors involved in the pathogenesis of spasmodic dysphonia. Spasmodic dysphonia is a task-specific focal laryngeal dystonia characterized by irregular and uncontrolled voice breaks. Pathogenesis of the disorder is poorly understood. Data Sources PubMed, Google Scholar, and Cochrane Library. Review Methods The data sources were searched using the following search terms: ( spasmodic dysphonia or laryngeal dystonia) and ( etiology, aetiology, diagnosis, pathogenesis, or pathophysiology). Conclusions Several potential etiological factors have been proposed by epidemiological, genetic, and neuropathological studies. Spasmodic dysphonia is a rare disorder primarily affecting females beginning in their 40s. Vocal tremor co-occurs in 30% to 60%. Large cohort studies identified risk factors such as a family history of neurological disorders including dystonia and tremor, recent viral illness, and heavy voice use. As none are rare events, a complex interactive process may contribute to pathogenesis in a small proportion of those at risk. Consequences to pathogenesis are neurological processes found in spasmodic dysphonia: loss of cortical inhibition, sensory processing disturbances, and neuroanatomical and physiological differences in the laryngeal motor control system. Implications for Practice Diagnosis of spasmodic dysphonia usually includes speech and laryngoscopic assessment. However, as diagnosis is sometimes problematic, measurement of neurophysiological abnormalities may contribute useful adjuncts for the diagnosis of spasmodic dysphonia in the future.

Implications of Synkinesis in Unilateral Vocal Fold Paralysis

Objectives

In patients with unilateral vocal fold paralysis (UVFP), laryngeal electromyography (LEMG) occasionally observes synkinesis in laryngeal muscles, a condition that could impair vocal fold mobility and voice control. This study aims to evaluate the impact of synkinesis on UVFP patients.

Study Design

A retrospective case-control study.

Setting

Medical center.

Subjects and Methods

Patients with UVFP onset >6 months were recruited (N = 104). The outcome measurements included LEMG, quantitative LEMG analysis of thyroarytenoid–lateral cricoarytenoid (TA-LCA) muscle complex, glottal gap measured by videolaryngostroboscopy, voice-related quality of life, and voice acoustic analysis.

Results

According to the LEMG analysis, 8 patients (8%) had synkinesis, and 96 (92%) did not. In the synkinesis group, TA-LCA turn frequency in the lesioned side was comparable to that in the healthy side ( P = .52). Patients in the synkinesis group had higher TA-LCA turn frequency ( P = .001), higher probability of cricothyroid muscle dysfunction ( P = .04), and better voice-related quality of life ( P = .01) but objective voice outcomes comparable to those in the nonsynkinesis group.

Conclusions

Patients with synkinesis will have near-complete restoration in TA-LCA turn frequency but still experience voice impairment, a finding that is compatible with the mechanism of aberrant reinnervation. However, patients with synkinesis have better disease-related quality of life than do those without synkinesis.

Time course of recovery of idiopathic vocal fold paralysis

OBJECTIVES/HYPOTHESIS

To clarify the time course of recovery in patients with idiopathic vocal fold paralysis.

STUDY DESIGN

Retrospective chart review.

METHODS

Medical records for all patients with idiopathic vocal fold paralysis over a 10-year period were reviewed to obtain demographic and clinical information, including onset of disease and recovery of vocal function. Stroboscopic exams of patients who recovered voice were reviewed blindly to assess return of vocal fold motion.

RESULTS

Thirty-eight of 55 patients (69%) recovered vocal function. Time course of recovery could be assessed in 34 patients who did not undergo injection augmentation. The mean time to recovery was 152.8 ± 109.3 days (left, 179.8 ± 111.3 days; right, 105.3 ± 93.7 days; P = .088). Two-thirds of patients recovered within 6 months. Probability of recovery declined over time. Five of 22 patients who recovered voice had return of vocal fold motion; 17 did not. The mean time to recovery did not differ between these groups (return of motion, 127.4 ± 132.3 days; no return of motion, 160.1 ± 105.1 days; P = .290).

CONCLUSIONS

Sixty-nine percent of patients with idiopathic vocal fold paralysis recovered vocal function, two-thirds doing so within 6 months of onset. Age, gender, laterality, use of injection augmentation did not influence recovery rate. Declining probability of recovery over time leads us to consider framework surgery after 6 months in patients with idiopathic paralysis.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:148-152, 2018.

The natural history of recoverable vocal fold paralysis: Implications for kinetics of reinnervation

OBJECTIVES/HYPOTHESIS

Patients with unilateral vocal fold paralysis (UVFP) are commonly told to wait 12 months for spontaneous recovery. This study aims to 1) determine the time to vocal recovery in UVFP, 2) use that data to develop a neurophysiologically plausible model for recovery, and 3) use the model to generate meaningful predictions for patient counseling.

STUDY DESIGN

Case series with de novo mathematical modeling.

METHODS

Patients with UVFP who could pinpoint a discrete onset of vocal improvement were identified. The time-to-recovery data were modeled by assuming an "early" recovery group with neuropraxia and a "late" recovery group with more severe nerve injury. For the late group, a two-stage model was developed to explain the time to recovery: regenerating axons must cross the site of injury in stage 1 (probabilistic), followed by unimpeded regrowth to the larynx in stage 2 (deterministic).

RESULTS

Of 727 cases of UVFP over a 7-year period, 44 reported spontaneous recovery with a discrete onset of vocal improvement. A hybrid distribution incorporating the two stages (exponentially modified Gaussian) accurately modeled the time-to-recovery data (R² = 0.918). The model predicts 86% of patients with recoverable UVFP will recover within 6 months, with 96% recovering within 9 months. Earlier vocal recovery is associated with recovery of vocal fold motion and younger age.

CONCLUSIONS

Waiting 12 months for spontaneous recovery is probably too conservative. Repair across the site of injury, and not regrowth to larynx, is likely the rate-determining step in reinnervation, consistent with other works on peripheral nerve regeneration.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:2585-2590, 2017.

Respiration-Related Laryngeal Electromyography in Children with Bilateral Vocal Fold Paralysis

We present 2 case reports to demonstrate the relationship between laryngeal muscle activity and respiration in children with bilateral vocal fold paralysis (BVFP) by simultaneous laryngeal electromyography (EMG) with recording of chest wall movement and intercostal muscle EMG. Laryngeal EMG was performed together with recording of chest wall movement in a 55-day-old girl who was undergoing tracheostomy for idiopathic congenital BVFP. Normal phasic activity was observed, ie, the thyroarytenoid (TA) muscle was active during expiration and the posterior cricoarytenoid (PCA) muscle during inspiration, suggesting a good prognosis for recovery. The child was decannulated at 11 months. Laryngeal EMG together with recording of chest wall movement and intercostal EMG in a 5-year-old girl who was tracheostomy-dependent following tracheoesophageal fistula repair due to BVFP showed phasic activity during expiration for both the TA and PCA muscles, indicating aberrant regeneration of the PCA motor nerve. The timing of laryngeal muscle activity with respiration in the assessment of pediatric congenital BVFP is essential to demonstrate the presence of normal or abnormal medullary respiratory neuronal input to laryngeal motoneurons. In cases in which BVFP is due to recurrent laryngeal nerve injury, respiration-related laryngeal EMG will identify aberrant regeneration. Laryngeal EMG should be combined with intercostal muscle EMG in the evaluation of children with significant vocal fold dysfunction of either central or peripheral origin.

Functional regeneration of the transected recurrent laryngeal nerve using a collagen scaffold loaded with laminin and laminin-binding BDNF and GDNF

Recurrent laryngeal nerve (RLN) injury remains a challenge due to the lack of effective treatments. In this study, we established a new drug delivery system consisting of a tube of Heal-All Oral Cavity Repair Membrane loaded with laminin and neurotrophic factors and tested its ability to promote functional recovery following RLN injury. We created recombinant fusion proteins consisting of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) fused to laminin-binding domains (LBDs) in order to prevent neurotrophin diffusion. LBD-BDNF, LBD-GDNF, and laminin were injected into a collagen tube that was fitted to the ends of the transected RLN in rats. Functional recovery was assessed 4, 8, and 12 weeks after injury. Although vocal fold movement was not restored until 12 weeks after injury, animals treated with the collagen tube loaded with laminin, LBD-BDNF and LBD-GDNF showed improved recovery in vocalisation, arytenoid cartilage angles, compound muscle action potentials and regenerated fibre area compared to animals treated by autologous nerve grafting (p < 0.05). These results demonstrate the drug delivery system induced nerve regeneration following RLN transection that was superior to that induced by autologus nerve grafting. It may have potential applications in nerve regeneration of RLN transection injury.

Consensus statement: Using laryngeal electromyography for the diagnosis and treatment of vocal cord paralysis

INTRODUCTION

The purpose of this study was to develop an evidence-based consensus statement regarding use of laryngeal electromyography (LEMG) for diagnosis and treatment of vocal fold paralysis after recurrent laryngeal neuropathy (RLN).

METHODS

Two questions regarding LEMG were analyzed: (1) Does LEMG predict recovery in patients with acute unilateral or bilateral vocal fold paralysis? (2) Do LEMG findings change clinical management in these individuals? A systematic review was performed using American Academy of Neurology criteria for rating of diagnostic accuracy.

RESULTS

Active voluntary motor unit potential recruitment and presence of polyphasic motor unit potentials within the first 6 months after lesion onset predicted recovery. Positive sharp waves and/or fibrillation potentials did not predict outcome. The presence of electrical synkinesis may decrease the likelihood of recovery, based on 1 published study. LEMG altered clinical management by changing the initial diagnosis from RLN in 48% of cases. Cricoarytenoid fixation and superior laryngeal neuropathy were the most common other diagnoses observed.

CONCLUSIONS

If prognostic information is required in a patient with vocal fold paralysis that is more than 4 weeks and less than 6 months in duration, then LEMG should be performed. LEMG may be performed to clarify treatment decisions for vocal fold immobility that is presumed to be caused by RLN. Muscle Nerve 53: 850-855, 2016.

Neurotrophin expression and laryngeal muscle pathophysiology following recurrent laryngeal nerve transection

Laryngeal palsy often occurs as a result of recurrent laryngeal or vagal nerve injury during oncological surgery of the head and neck, affecting quality of life and increasing economic burden. Reinnervation following recurrent laryngeal nerve (RLN) injury is difficult despite development of techniques, such as neural anastomosis, nerve grafting and creation of a laryngeal muscle pedicle. In the present study, due to the limited availability of human nerve tissue for research, a rat model was used to investigate neurotrophin expression and laryngeal muscle pathophysiology in RLN injury. Twenty-five male Sprague-Dawley rats underwent right RLN transection with the excision of a 5-mm segment. Vocal fold movements, vocalization, histology and immunostaining were evaluated at different time-points (3, 6, 10 and 16 weeks). Although vocalization was restored, movement of the vocal fold failed to return to normal levels following RLN injury. The expression of brain‑derived neurotrophic factor and glial cell line-derived neurotrophic factor differed in the thyroarytenoid (TA) and posterior cricoarytenoid muscles. The number of axons did not increase to baseline levels over time. Furthermore, normal muscle function was unlikely with spontaneous reinnervation. During regeneration following RLN injury, differences in the expression levels of neurotrophic factors may have resulted in preferential reinnervation of the TA muscles. Data from the present study indicated that neurotrophic factors may be applied for restoring the function of the laryngeal nerve following recurrent injury.

Synkinesis following recurrent laryngeal nerve injury: A computer simulation

OBJECTIVES/HYPOTHESIS

When the recurrent laryngeal nerve (RLN) is injured, functional recovery may be limited by the number of axons that regrow across the site of injury, and by the proportions of these axons that reinnervate the antagonistic muscle (synkinesis). This process was investigated in a computer model of RLN recovery.

STUDY DESIGN

Computer simulation.

METHODS

The developed computer program accepted as inputs: number of RLN axons; proportions of axons originally innervating adductor versus abductor, fraction of axons transected, fraction of axons that grow back, and width of 1 standard deviation about the mean. The program employed random sampling from a normal distribution to model various degrees of recovery, using random numbers to assign each axon to the correct muscle, an incorrect muscle, or no recovery. Each simulation was run 1,000×, and the mean, highest, and lowest degrees of synkinesis were determined.

RESULTS

More severe injuries were associated with greater degrees of synkinesis. Extremes of synkinesis were possible but were rare. One example result, for a 50% injury with a 50% recovery rate, found: in the adductor muscles, 74.8% of axons will be innervated, of which 49.2% are the original uninjured axons, 19.4% are recovered adductor axons, and 6.2% are misdirected abductor axons. In the posterior cricoarytenoid (PCA), these values were 75.7%, 50.8%, 6.1%, and 18.8%, respectively. Results of many such simulations are plotted.

CONCLUSIONS

Laryngeal synkinesis can be simulated based on known anatomic ratios and estimated recovery rates. The PCA is invariably much more affected by synkinetic reinnervation than are the adductor muscles.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:1600-1605, 2016.

Magnetic Control of the Glottic Opening in an Ex Vivo Sheep Larynx Model: A Preliminary Study

OBJECTIVE/HYPOTHESIS

So far, a number of techniques have been described for the treatment of bilateral vocal fold paralysis. These techniques were reported to be successful in maintaining an adequate airway but also found to be associated with an increased risk of aspiration, dysphonia, and granulation tissue formation at the operation site. We aimed to investigate the effectiveness of a novel mucosa-sparing technique based on the generation of a magnetic field within the larynx for the tailored lateralization of the ipsilateral vocal fold.

STUDY DESIGN

This is an ex vivo experimental study.

METHODS

Twenty sheep larynges that were procured from the local slaughterhouse were used as a model. For each specimen, two neodymium (Nd) disc magnets with marked poles were used to create a unilateral attractive magnetic force at the glottic level. Following insertion of the magnets, the level of vocal fold lateralization was assessed under an operating microscope. The results were analyzed for their statistical significance.

RESULTS

Before the procedure, the mean value of the glottic openings of all the specimens was 4.985 mm. The postprocedure mean value was 5.640 mm. The mean amount of increase in the glottic openings after the procedure was 0.655 mm. This change was found to be statistically significant (P < 0.05).

CONCLUSIONS

A statistically significant increase in the cross-sectional area of the glottic region could be achieved. The mucosal integrity of the laryngeal airway was also preserved. The idea of "magnetic control of the glottic airway" is a novel concept but seems to be a promising option.

Quantitative laryngeal electromyography assessment of cricothyroid function in patients with unilateral vocal fold paralysis

OBJECTIVES/HYPOTHESIS

Determination of superior laryngeal nerve (SLN) involvement in addition to recurrent laryngeal nerve (RLN) paralysis in patients with unilateral vocal fold paralysis (UVFP) relies on traditional, qualitative laryngeal electromyography (LEMG) examination. It is necessary to develop a quantitative measurement that reflects the degree of denervation of the cricothyroid (CT) muscle. The present study aimed to establish a standard quantitative assessment of CT function in patients with UVFP by measuring the turn frequency.

STUDY DESIGN

Case series study performed in an otolaryngology outpatient clinic.

METHODS

Twenty healthy subjects and 103 patients with UVFP were recruited. The main outcome measures for the patients included acoustic analysis using traditional LEMG examination, quantitative LEMG analysis, and acoustic analysis based on fundamental frequency contours.

RESULTS

Acoustic reliability was examined in the healthy subjects, and the peak fundamental frequency in an upward glissando showed good test-retest reliability, especially for the offset fundamental frequency. LEMG indicated that 33 patients had RLN and SLN lesions (RLN+SLN group) and 70 had only RLN lesions (RLN group). When patients produced a standard upward glissando sound, the peak turn frequency reflecting the recruitment of the CT muscle was significantly lower in the RLN+SLN group compared with the RLN group (406±256 vs. 778±238 Hz; P<.001).

CONCLUSIONS

We conclude that quantitative measurement of the interference pattern when voicing a standard upward glissando sound may provide a feasible reflection of the degree of a SLN injury.

LEVEL OF EVIDENCE

4.

Diagnosis and management with botulinum toxin in 11 cases of laryngeal synkinesis

Laryngeal synkinesis is a vocal fold movement disorder produced by a misdirected reinnervation after a recurrent laryngeal nerve injury. Its symptoms differ greatly between patients, requiring diverse therapeutical approaches. We aim to describe our experience in the diagnosis and treatment of different laryngeal synkinesis presentations. 11 patients diagnosed between 2011 and 2014 in a tertiary referral center with laryngeal synkinesis confirmed by laryngeal electromyography were included in our study. All medical records and laryngoscopic and electromyographic data were reviewed retrospectively. Four patients had previous unilateral vocal fold palsy and seven had a bilateral palsy with different degrees of clinical involvement. All of them showed paradoxical movements during inhalation in videofibrolaryngoscopic examination. Laryngeal electromyography confirmed the diagnosis of laryngeal synkinesis. Dyspnea was the main presentation symptom. Three patients with mild symptoms were not treated. Patients with unilateral vocal fold immobility were successfully treated with periodic botulinum toxin injections. Patients with bilateral immobility had a good initial response to botulinum toxin, although in some of them, a posterior cordectomy had to be finally performed. In conclusion, laryngeal synkinesis is a heterogeneous clinic entity that appears in patients with unilateral or bilateral vocal fold paralysis. Videofibrolaryngoscopy and laryngeal electromyography are essential to a correct diagnosis. Botulinum toxin injections are the main treatment for symptomatic cases, even if in bilateral palsy cases more aggressive treatments are often required.

Partial Recurrent Laryngeal Nerve Paralysis or Paresis? In Search for the Accurate Diagnosis

“Partial paralysis” of the larynx is a term often used to describe a hypomobile vocal fold as is the term “paresis.” We present a case of a dysphonic patient with a mobility disorder of the vocal fold, for whom idiopathic “partial paralysis” was the diagnosis made after laryngeal electromyography, and discuss a proposition for a different implementation of the term.

Unilateral vocal fold paralysis: can laryngoscopy predict recovery? A prospective study

OBJECTIVE

To determine the prognostic value of laryngoscopy in predicting the recovery of unilateral vocal fold paralysis.

METHOD

A prospective study was carried out of all patients with unilateral vocal fold paralysis without a progressive lesion or arytenoid dislocation.

RESULTS

Among the 66 candidates, 15 recovered. Patients with interarytenoid paralysis (p < 0.001) or posterolateral tilt of the arytenoid (p = 0.028) had less chance of recovery. Among 51 patients who did not recover, 25.49 per cent regained phonatory function by compensatory movement of the normal side; the rest required an intervention. Intervention requirement was significantly less for those patients who had isolated glottic level compensation. The paralysed vocal fold was at the same level in 32.35 per cent of patients, higher in 38.23 per cent and lower in 29.42 per cent. In those in whom vocal folds were in the abducted position (46.67 per cent), the affected vocal fold was at a lower position on phonation. Inter-observer reliability assessment revealed excellent to good agreement for all criteria.

CONCLUSION

Interarytenoid paralysis and posterolateral tilt of the arytenoid were predictors of poor recovery.

Acquired bilateral adductor laryngeal paralysis in neonates and children: a case series and a systematic review

OBJECTIVES

To present a series of acquired bilateral adductor laryngeal paralysis (BAdLP) and review the literature on clinical manifestations and management.

METHODS

A retrospective review of a single tertiary care practice of pediatric otolaryngology was conducted. Patients were identified from a surgical database spanning twelve years of practice (2002-2013). The variables documented included gender, age at presentation, co-morbid conditions, documented laryngeal findings on endoscopy, management and outcome. A systematic review of the literature was conducted to identify reports on BAdLP in children and associated conditions.

RESULTS

Five cases (four girls and one boy) ranging from 3 months to 16 years of age were identified. All cases were documented using rigid and/or flexible laryngoscopy. In four cases, the onset was after major cardiac surgery complicated by cerebral vascular accidents, while one followed a thalamic stroke. Four were managed with tube feeding. Only three papers reported BAdLP in children.

CONCLUSIONS

The cases identified were all acquired after a central neurological insult. The profile is distinct from the congenital adductor form of laryngeal paralysis previously described. However, the symptom complex is identical. We believe this is the largest case series from one center to be reported.

Stem cell-derived tissue-engineered constructs for hemilaryngeal reconstruction

OBJECTIVES

As an initial step toward our goal of developing a completely tissue-engineered larynx, the aim of this study was to describe and compare three strategies of creating tissue-engineered muscle-polymer constructs for hemilaryngeal reconstruction.

METHODS

Cartilage-mimicking polymer was developed from electrospun poly(D,L-lactide-co-ε-caprolactone) (PCL). Primary muscle progenitor cell cultures were derived from syngeneic F344 rat skeletal muscle biopsies. Twenty F344 rats underwent resection of the outer hemilaryngeal cartilage with the underlying laryngeal adductor muscle. The defects were repaired with muscle stem cell-derived muscle-PCL constructs (5 animals), myotube-derived muscle-PCL constructs (5 animals), motor end plate-expressing muscle-PCL constructs (5 animals), or PCL alone (controls; 5 animals). The outcome measures at 1 month included animal survival, muscle thickness, and innervation status as determined by electromyography and immunohistochemistry.

RESULTS

All of the animals survived the 1-month implant period and had appropriate weight gain. The group that received motor end plate-expressing muscle-PCL constructs demonstrated the greatest muscle thickness and the strongest innervation, according to electromyographic activity and the percentage of motor end plates that had nerve contact.

CONCLUSIONS

Although all of the tissue-engineered constructs provided effective reconstruction, those that expressed motor end plates before implantation yielded muscle that was more strongly innervated and viable. This finding suggests that this novel approach may be useful in the development of a tissue-engineered laryngeal replacement.

Laryngeal muscle activity in unilateral vocal fold paralysis patients using electromyography and coronal reconstructed images

OBJECTIVE

To assess laryngeal muscle activity in unilateral vocal fold paralysis (UVFP) patients using laryngeal electromyography (LEMG) and coronal images.

STUDY DESIGN

Case series with chart review.

SETTING

University hospital.

SUBJECTS AND METHODS

Twenty-one patients diagnosed with UVFP of at least 6 months in duration with paralytic dysphonia, underwent LEMG, phonatory function tests, and coronal imaging. A 4-point scale was used to grade motor unit (MU) recruitment: absent = 4+, greatly decreased = 3+, moderately decreased = 2+, and mildly decreased = 1+. Maximum phonation time (MPT) and mean flow rate (MFR) were employed. Coronal images were assessed for differences in thickness and vertical position of the vocal folds during phonation and inhalation.

RESULTS

MU recruitment in thyroarytenoid/lateral cricoarytenoid (TA/LCA) muscle complex results were 1+ for 4 patients, 2+ for 5, 3+ for 6, and 4+ for 6. MPT was positively correlated with MU recruitment. Thinning of the affected fold was evident during phonation in 19 of the 21 subjects. The affected fold was at an equal level with the healthy fold in all 9 subjects with MU recruitment of 1+ and 2+. Eleven of 12 subjects with MU recruitments of 3+ and 4+ showed the affected fold at a higher level than the healthy fold. There was a significant difference between MU recruitment and the vertical position of the affected fold.

CONCLUSIONS

Synkinetic reinnervation may occur in some cases with UVFP. MU recruitments of TA/LCA muscle complex in UVFP patients may be related to phonatory function and the vertical position of the affected fold.

Spontaneous laryngeal reinnervation following chronic recurrent laryngeal nerve injury

OBJECTIVES/HYPOTHESIS

To enhance understanding of spontaneous laryngeal muscle reinnervation following severe recurrent laryngeal nerve injury by testing the hypotheses that 1) nerve fibers responsible for thyroarytenoid muscle reinnervation can originate from multiple sources and 2) superior laryngeal nerve is a source of reinnervation.

STUDY DESIGN

Prospective, controlled, animal model.

METHODS

A combination of retrograde neuronal labeling techniques, immunohistochemistry, electromyography, and sequential observations of vocal fold mobility were employed in rat model of chronic recurrent laryngeal nerve injury. The current study details an initial set of experiments in sham surgical and denervated group animals and a subsequent set of experiments in a denervated group.

RESULTS

At 3 months after recurrent laryngeal nerve resection, retrograde brainstem neuronal labeling identified cells in the characteristic superior laryngeal nerve cell body location as well as cells in a novel caudal location. Regrowth of neuron fibers across the site of previous recurrent laryngeal nerve resection was seen in 87% of examined animals in the denervated group. Electromyographic data support innervation by both the superior and recurrent laryngeal nerves following chronic recurrent laryngeal nerve injury.

CONCLUSIONS

Following chronic recurrent laryngeal nerve injury in the rat, laryngeal innervation is demonstrated through the superior laryngeal nerve from cells both within and outside of the normal cluster of cells that supply the superior laryngeal nerve. The recurrent laryngeal nerve regenerates across a surgically created gap, but functional significance of regenerated nerve fibers is unclear.