Vocal cord paralysis, synkinesis and vocal fold motion impairment

Development and regeneration of the vagus nerve

The vagus nerve, with its myriad constituent axon branches and innervation targets, has long been a model of anatomical complexity in the nervous system. The branched architecture of the vagus nerve is now appreciated to be highly organized around the topographic and/or molecular identities of the neurons that innervate each target tissue. However, we are only just beginning to understand the developmental mechanisms by which heterogeneous vagus neuron identity is specified, patterned, and used to guide the axons of particular neurons to particular targets. Here, we summarize our current understanding of the complex topographic and molecular organization of the vagus nerve, the developmental basis of neuron specification and patterned axon guidance that supports this organization, and the regenerative mechanisms that promote, or inhibit, the restoration of vagus nerve organization after nerve damage. Finally, we highlight key unanswered questions in these areas and discuss potential strategies to address these questions.

Selective zygomaticus muscle activation by ball electrodes in synkinetically reinnervated patients after facial paralysis

Introduction

Although many different treatments were developed for facial palsy, only a few therapeutic options are available for facial synkinesis. Electrical stimulation of specific muscles via implants could be useful in restoring facial symmetry in synkinetic patients. A challenge in developing stimulation devices is finding the right stimulation location, type, and amplitude. This work assesses the ability to selectively stimulate the zygomaticus muscle (ZYG) in patients with oral-ocular synkinesis to elicit a visually detectable response of the ipsilateral corner of the mouth (COM), without causing a reaction of the orbicularis oculi muscle (OOM). We aimed to assess how close to the COM the stimulation should be delivered in order to be selective.

Methods

A total of 10 patients (eight females, two males) were enrolled. Facial function was graded according to the Sunnybrook facial grading system. Needle EMG was used to test the activities of the muscles, during volitional and "unintended" movements, and the degree of synkinesis of the ZYG and OOM. Two ball electrodes connected to an external stimulator were placed on the paretic ZYG, as close as possible to the COM.

Results

Independent of the waveform with which the stimulation was presented, a selective ZYG response was observed within 4.5 cm of the horizontal plane and 3 cm of the vertical plane of the COM. When the distance between the electrodes was kept to ≤2 cm, the amplitude necessary to trigger a response ranged between 3 and 6 mA when the stimulation was delivered with triangular pulses and between 2.5 and 3.5 mA for rectangular pulses. The required amplitude did not seem to be dependent on the applied phase duration (PD), as long as the PD was ≥5 ms.

Conclusion

Our results show that selective stimulation of the ZYG presenting synkinetic ZYG-OOM reinnervation can be achieved using a broad PD range (25-1,000 ms) and an average amplitude ≤6 mA, which may be further decreased to 3.5 mA if the stimulation is delivered via rectangular rather than triangular waves. The most comfortable and effective results were observed with PDs between 50 and 250 ms, suggesting that this range should be selected in future studies.

Clinical Trial Registration

[https://drks.de/search/de/trial/DRKS00019992], identifier (DRKS00019992).

Temporal expression of Laminin-111 in the developing rat larynx

Laminin-111 is a basement membrane protein that participates in motor innervation and reinnervation. During axonal pathfinding, laminin-111 interacts with netrin-1 (NTN1) and changes its attractant growth cone properties into repulsion. While previous models of recurrent laryngeal nerve (RLN) transection show increased Laminin-111 and NTN1 production after injury, developmental expression in the larynx has not been defined. This study investigates the expression of laminin-111 in laryngeal muscles during primary laryngeal innervation of Sprague Dawley rats. Adult larynges and embryos were sectioned for immunohistochemistry with βIII-Tubulin, laminin subunit α-1 (LAMA1), NTN1, and α-bungarotoxin. Sections were processed for single-molecule inexpensive RNA fluorescence in situ hybridization analysis of LAMA1 mRNA. LAMA1 expression increased in all intrinsic laryngeal muscles, except the medial thyroarytenoid (MTA), at E20.5. At E20.5 there was increased expression in the lateral thyroarytenoid (LTA) and posterior cricoarytenoid (PCA) compared to the MTA. NTN1 upregulation was limited to the LTA and lateral cricoarytenoid (LCA) at E16.5 without any increase in the MTA or PCA. LAMA1 and NTN1 expression did not strictly follow expected patterns relative to the known timing of innervation and does not appear to be acting similarly to its role following RLN injury. These differences between developmental and post-injury innervation provide targets for investigations of therapeutics after nerve injury.

Superior Laryngeal Nerve Block for Treatment of Neurogenic Cough

OBJECTIVES

This study aimed to add to the body of evidence for efficacy of Superior Laryngeal Nerve (SLN) blocks for treatment of neurogenic cough. Efficacy at short- and long-term intervals are presented as well as relationships with laryngoscopic findings.

METHODS

A retrospective chart review of patients treated with SLN block between 2018 and 2020 was conducted. Patient demographics, videostroboscopic findings, and patient-subjective perception of outcomes were recorded and analyzed. Cough Severity Index (CSI) scores from pre-injection, short-term follow-up, and long-term follow-up were compared.

RESULTS

Twenty patients underwent SLN block in the clinic setting. Four patients were excluded for incomplete records. The indication was neurogenic cough refractory to medical management and/or cough suppression therapy. Patients with short-term follow-up (n = 13) had statistically significant decrease in CSI scores, with a mean baseline CSI of 24.3 decreasing to 16.15 (P = .006). Patients with evidence of Vocal Fold Motion/Vibratory Abnormalities (VFA) (n = 8) showed improvement in short-term CSI scores, with a mean baseline CSI of 24.13 decreasing to 14.5 (P = .004). Those without evidence of VFA did not have statistically significant improvement in short-term CSI scores. At long-term follow-up, patients with VFA had improvements that approached statistical significance with a mean baseline CSI of 22.56 decreasing to 14.56 (P = .057), while patients without VFA showed no improvement.

CONCLUSIONS

Our results are consistent with previous literature indicating efficacy of SLN block. The presence of VFA may be an indicator of patients who experience increased therapeutic effect.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Regularity of voice recovery and arytenoid motion after closed reduction in patients with arytenoid dislocation: a self-controlled clinical study

Background: Closed reduction is an effective treatment for arytenoid dislocation. The treatment is usually given more than once to obtain normal voice. However, when to perform the next closed reduction remains controversial.Objective: This study aimed to observe the regularity of the voice recovery and the arytenoid motion in patients with arytenoid dislocation after closed reduction.Material and methods: Thirty-one patients were recruited from September 2017 to April 2019. Results of their clinical data were reviewed retrospectively.Results: Among the thirty-one patients, their VHI scores, F0, jitter%, shimmer%, glottal-to-noise excitation %(GNE), maximum phonation time (MPT) and GRBAS Scale (G, R, B, A) improved significantly (p < .05), but there was no statistically significant difference for GRBAS Scale (S) (p>.05). The duration between last closed reduction and the restoring normal voice ranged from 1-8 days, with a mean of 4.65 ± 0.57 days, at the same time the glottis was completely closed.Conclusions and significance: Closed reduction for patients with arytenoid dislocation is an effective procedure. A time window between 4.08th and 5.22th day (at a confidence level of 95%) after the last closed reduction was identified to be critical for voice recovery.

Olfactory Ecto-Mesenchymal Stem Cells in Laryngeal Nerve Regeneration in Rats

Selective intralaryngeal reinnervation has been shown to be effective in experimental models. This consists of independently reinnerving the adductor and abductor of laryngeal muscles of the larynx, in order to prevent any misalignment of the axonal regrowth, improve the functional recovery and tend toward reduction of synkinesis. The surgical technique remains complex. Current research focuses on simplifying and improving this technique. Olfactory ectomesenchymal stem cells (OEMSC) represent an interesting candidate for cell therapy and could be obtained from olfactory mucosa. Recent reports suggest a neuroregenerative potential in various animal models of central and peripheral nervous systems injuries. The aim of this study was dual: to develop a simple surgical model of selective reinnervation applicable in humans and to evaluate the relevance of OEMSC-based cell therapy for improving axonal guidance. Eight Fisher syngeneic rats were used to carry out the OEMSCs culture. Thirty-four Fisher syngeneic rats were operated on, divided into three groups depending on the transplanting. For all the rats, we have performed a side to end anastomosis of the vagal nerve with the inferior laryngeal nerve by interposition of a nerve graft from the left femoral nerve. Then, the first group didn't have any injection, the second group has an injection of thrombin and the third group has an injection of one million EOMSCs. Three months after surgery, laryngeal muscle activity was evaluated by videolaryngoscopy and electromyography recordings. In order to illustrate the quality of axonal regrowth, a fluorescent tracer was injected into the right posterior crico-arytenoid muscle (PCA) to reveal the cellular bodies of the motoneurons responsible for reinnervation of the PCA in the central nervous system. In our study, no improvement was found during the videolaryngological functional evaluation or with regard to the electrical activity of the PCA muscle. The cells colabelled in retrograde tracing were numerous in all groups, reflecting abnormal axonal regeneration. The interposition of a nerve graft, as side to end anastomosis between the vagus nerve and the inferior laryngeal nerve, filled with OEMSCs, does not provide better reinnervation of a hemilarynx.

Laryngeal adductor function following potassium titanyl phosphate laser welding of the recurrent laryngeal nerve

OBJECTIVES/HYPOTHESIS

Recurrent laryngeal nerve (RLN) transection injuries may occur during thyroidectomy and other surgical procedures. Laser nerve welding has been shown to cause less technique-related axonal damage than the traditional suture method. We compared functional adductor results using these two methods of RLN repair.

STUDY DESIGN

Animal model.

METHODS

Canine hemilarynges underwent pretreatment testing of laryngeal adductor function, followed by RLN transection and repair using potassium titanyl phosphate (KTP) laser welding (n = 8) or microneural suture (n = 16) techniques. Six months later, adductor function was measured again and expressed as a proportion of the pretreatment value.

RESULTS

The mean laryngeal adductor pressure ratios were 82.4% (95% confidence interval [CI]: 72.8%-92.0%) for the laser repair group and 55.5% (95% CI: 49.4%-61.6%) for the suture control group, with a difference of 26.9% (95% CI: 15.3%-38.5%). Both spontaneous and stimulated glottic closure was observed in the laser welding and microsuture repair groups.

CONCLUSIONS

Laser nerve welding resulted in greater strength of adduction than suture repair of an acutely transected RLN. Suture anastomosis may traumatize more axons than the laser. Stronger vocal fold adduction is associated clinically with better protection from aspiration and improved voice outcomes. KTP laser welding should be considered for anastomosis of the RLN and other nerves.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:1764-1769, 2020.

Recurrent Laryngeal Nerve Reinnervation in Rats Posttransection: Neurotrophic Factor Expression over Time

OBJECTIVE

Recurrent laryngeal nerve (RLN) injury causes vocal fold paralysis from which functional recovery is typically absent due to nonselective reinnervation. This study investigates expression of axon guidance cues and their modulators relative to the chronology of reinnervation by examining the expression of glial-derived neurotrophic factor (GDNF), netrin 1, and laminin 111 (LAMA1) in nonpooled laryngeal muscles. This study is the first to describe the post-RLN injury expression pattern of LAMA1, a target of particular interest as it has been shown to switch netrin 1-mediated growth cone attraction to repulsion.

STUDY DESIGN

Animal experiment (rat model).

SETTING

Basic science laboratory.

METHODS

The right RLNs of 64 female Sprague-Dawley rats were transected, with sacrifice at 1, 3, 7, 21, 28, and 56 days postinjury (DPI). Single-animal messenger RNA was isolated from the ipsilateral posterior cricoarytenoid (PCA), lateral thyroarytenoid (LTA), and medial thyroarytenoid (MTA) for quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Immunostaining for LAMA1 expression was performed in the same muscles.

RESULTS

LAMA1 was elevated in the PCA at 3 to 56 DPI, LTA at 7 DPI, and MTA at 14 and 28 DPI. This correlates with the chronology of laryngeal reinnervation. Using a new protocol, single-animal muscle qRT-PCR possible and expression results for GDNF and netrin 1 were similar to previous pooled investigations.

CONCLUSION

Reliable qRT-PCR is possible with single rat laryngeal muscles. The expression of netrin 1 and LAMA1 is chronologically coordinated with muscle innervation in the LTA and MTA. This suggests that LAMA1 may influence netrin 1 to repel axons and delay LTA and MTA reinnervation.

Complete and incomplete recurrent laryngeal nerve injury after thyroid and parathyroid surgery: Characterizing paralysis and paresis

BACKGROUND

Injury of the recurrent laryngeal nerve and consequent disorder of vocal fold movement is a typical complication in thyroid and parathyroid surgery. During postoperative laryngoscopy we observed not only a complete standstill (vocal fold paralysis), but also a hypomobility (paresis). In this prospective study, we investigated the difference in incidence and prognosis as well as risk-factors, intraoperative neuromonitoring, and symptoms between vocal fold paralysis and vocal fold paresis.

METHODS

Data were prospectively collected and analyzed in a single high-volume thyroid center between 2012 and 2016. Vocal fold paresis was defined as hypomobility in abduction or adduction, a reduction in range and speed of vocal fold movement. Vocal fold paralysis was defined as asymmetry and missing purposeful vocal fold movement.

RESULTS

The study included 4,707 surgeries and 7,992 at-risk nerves at risk. Vocal fold paralysis was diagnosed in 374 patients (4.68% of 7,992 nerves at risk) and vocal fold paresis in 114 patients (1.43%). Exclusively in the paralysis group, 36 patients (0.45%) developed permanent loss of vocal fold function (P < .001). In follow-up, vocal fold paresis patients regain normal vocal fold function significantly earlier than vocal fold paralysis (mean duration: 6.96 ± 6.506 vs 10.77 ± 7,827 weeks) and presented with significantly less symptoms like hoarseness, diplophonia, dysphagia, and dyspnea (68.8% vs 95.9 %). In intraoperative neuromonitoring, vocal fold paresis showed a significantly higher postresectional N. vagus amplitude than vocal fold paralysis patients (0.349 mV vs 0.114 mV, P < .001).

CONCLUSION

After thyroidectomy, vocal fold paresis must be distinguished from vocal fold paralysis and should be implemented as a separate outcome parameter in the postoperative quality assessment.

Expression of trophic factors receptors during reinnervation after recurrent laryngeal nerve injury

OBJECTIVE

An injury of the recurrent laryngeal nerve (RLN) triggers axonal regeneration but results in a poor functional recovery. Netrin-1 and glial cell-derived neurotrophic factor (GDNF) expression are up-regulated in laryngeal muscles during RLN regeneration, but the role of their receptors produced in the nucleus ambiguus is unknown. The aim of this work was to determine the timing of the production of Netrin-1 and GDNF receptors during RLN regeneration and correlate this with the previously identified timing of up-regulation of their trophic factors in the laryngeal muscles.

STUDY DESIGN

Laboratory experiment with rat model.

METHODS

The right RLN was transected and dextran amine tracer applied. At 7, 14, and 21 days postinjury (DPI), brainstems were removed and harvested. Immunostaining was performed for Netrin-1 (deleted in colorectal carcinoma [DCC], UNC5A) and GDNF receptors (rearranged during transfection [Ret], glycosylphosphatidylinositol-linked cell surface receptors [GFRα1, GFRα2, GFRα3]). The timing and type of receptor production relative to injury as well as their position in the nucleus ambiguus was analyzed.

RESULTS

Netrin-1 UNC5A receptors were minimal in the nucleus ambiguus during RLN regeneration. DCC, the receptor that plays an attract role, was immunopositive from 7 to 21 DPI. All GDNF receptors, except GFRα2, were clearly positive from 7 to 14 DPI. No differences of production were observed according to the position of the motor neurons in the nucleus ambiguus.

CONCLUSION

An injury of the RLN leads to a higher production of Netrin-1 DCC and GDNF receptors in the nucleus ambiguus. The timing of receptor production is similar to up-regulation of their trophic factors in the laryngeal muscles.

LEVEL OF EVIDENCE

NA. Laryngoscope, 129:2537-2542, 2019.

Perspectives on voice treatment for unilateral vocal fold paralysis

PURPOSE OF REVIEW

Unilateral vocal fold paralysis (UVFP) is a common cause of neurogenic dysphonia resulting in glottal insufficiency. To restore glottal sufficiency and reduce the presenting dysphonia, treatment involving either surgical intervention, voice therapy or a combination of the two is typically provided. Currently, there is no consensus for the most effective voice treatment for UVFP. This results in an inability to compare current studies, and a lack of treatment effectiveness for the management of UVFP. This study aims to review the most recent literature for the management of dysphonia due to UVFP to establish the current evidence base for voice treatment options.

RECENT FINDINGS

There was found to be a lack of consistency in the rationale, selection and timing of the surgical intervention and/or voice therapy being provided for patients with UVFP.

SUMMARY

Further consensus is required for the rationale and selection of voice treatment prescriptions for the management of UVFP in order to improve treatment effectiveness and voice outcomes in patients with UVFP.

Recovery of Voice After Reconstruction of the Recurrent Laryngeal Nerve and Adjuvant Nimodipine

Background

Transection injury to the recurrent laryngeal nerve (RLN) has been associated with permanent vocal fold palsy, and treatment has been limited to voice therapy or local treatment of vocal folds. Microsurgical repair has been reported to induce a better function. The calcium channel antagonist nimodipine improves functional recovery after experimental nerve injury and also after cranial nerve injury in patients. This study aims to present voice outcome in patients who underwent repair of the RLN and received nimodipine during regeneration.

Methods

From 2002–2016, 19 patients were admitted to our center with complete unilateral injury to the RLN and underwent microsurgical repair of the RLN. After nerve repair, patients received nimodipine for 2–3 months. Laryngoscopy was performed repeatedly up to 14 months postoperatively. The Voice Handicap Index (VHI) was administered, and patients’ maximum phonation time (MPT) was recorded during the follow-up.

Results

All patients recovered well after surgery, and nimodipine was well tolerated with no dropouts. None of the patients suffered from atrophy of the vocal fold, and some patients even showed a small ab/adduction of the vocal fold on the repaired side with laryngoscopy. During long-term follow-up (>3 years), VHI and MPT normalized, indicating a nearly complete recovery from unilateral RLN injury.

Conclusions

In this cohort study, we report the results of the first 19 consecutive cases at our center subjected to reconstruction of the RLN and adjuvant nimodipine treatment. The outcome of the current strategy is encouraging and should be considered after iatrogenic RLN transection injuries.

[The diagnostics and treatment of bilateral paralysis of the larynx]

The objective of the present study was to consider the currently available methods for the diagnostics and treatment of the patients presenting with bilateral paralysis of the larynx of various etiologies. We undertook the analysis of the publications in the domestic and foreign scientific literature concerning diagnosis and treatment of bilateral paralysis of the larynx. It was found that despite the existing modern high-tech diagnostic technologies and the variety of surgical methods for the treatment of this condition, the problem of diagnostics, management, and rehabilitation of the patients suffering from bilateral paralysis of the larynx remains a serious challenge for the researchers and clinicians that requires further investigation of this pathology. For the correct and timely diagnosis of bilateral paralysis of the larynx, the comprehensive evaluation of the functional state of the neuromuscular apparatus of the larynx is necessary. The key prerequisites for the success of the surgical intervention are its timeliness and the choice of the optimal surgical modalities.

The Anastomoses of the Recurrent Laryngeal Nerve in the Larynx: A Meta-Analysis and Systematic Review

OBJECTIVES

The recurrent laryngeal nerve and its branches form a great variety of anastomoses. These nerve communications can alter the innervation patterns of the laryngeal muscles and can affect both the diagnosis and treatment of paralyzed vocal cords. The aim of this study was to assess the prevalence and anatomical characteristics of the laryngeal nerve connections, and to review their function and clinical significance.

STUDY DESIGN

Meta-analysis and systematic review.

METHODS

The major electronic databases were thoroughly searched to identify all studies reporting data on the anastomoses of the laryngeal nerves. Data on the prevalence of each type of anastomosis were extracted and pooled into a meta-analysis using MetaXL version 3.0 (EpiGear International Pty. Ltd., Wilston, Queensland, Australia).

RESULTS

Twenty-two cadaveric studies (n = 1404 hemilarynges) were included in the meta-analysis. The two most common communications were Galen's anastamosis and the arytenoid plexus. The pooled prevalence estimate for Galen's anastamosis was 76.7% (95% confidence interval [CI]: 59.0-90.0), of which the single trunk type was most common (92.3%). The arytenoid plexus had a pooled prevalence estimate of 79.7% (95% CI: 41.1-100).

CONCLUSIONS

Owing to the high prevalences and variability of nerve connections in the larynx, detailed anatomical knowledge of these anastomoses can be crucial for the accurate interpretation of laryngoscopy results, reducing iatrogenic injury during surgical procedures, and facilitating the development of novel strategies for treating laryngeal paralyses.

Value of Laryngeal Electromyography in Diagnosis of Vocal Fold Immobility

Objectives:

We sought to determine the value of laryngeal electromyography (LEMG) and evoked LEMG in the diagnosis of vocal fold immobility.

Methods:

We analyzed 110 cases of vocal fold immobility by their clinical manifestations and LEMG characteristics, including spontaneous potential activity, motor unit potential measurement, recruitment pattern analysis, and evoked LEMG signals.

Results:

With LEMG, we identified 87 patients with neuropathic laryngeal injuries. Neurogenic vocal fold immobility showed a wide variety of abnormal activity. Fibrillation potentials and positive sharp waves were found in patients with laryngeal nerve injuries. For laryngeal paralysis, there was no reaction with LEMG and evoked LEMG. For incomplete laryngeal paralysis, decreased evoked LEMG signals were also seen with delayed latency (thyroarytenoid muscle, 2.2 ± 1.0 ms, p < 01; posterior cricoarytenoid muscle, 2.4 ± 1.0 ms, p < .05) and lower amplitude (thyroarytenoid muscle, 0.9 ± 0.7 mV, p < .05; posterior cricoarytenoid muscle, 1.2 ± 1.0 mV, p < .01). Nineteen patients with vocal fold mechanical limitations generally had normal LEMG and evoked LEMG signals. Four patients with neoplastic infiltration of the laryngeal muscles demonstrated abnormal LEMG signals but nearly normal evoked LEMG signals.

Conclusions:

We conclude that LEMG and evoked LEMG behavior plays a crucial role in the diagnosis of vocal fold immobility. The decreased recruitment activities on LEMG and the decreased evoked LEMG signals with longer latency and lower amplitude reflect the severity of neuropathic laryngeal injury.

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.

Arytenoid abduction for bilateral vocal fold immobility

PURPOSE OF REVIEW

The pathophysiology of bilateral vocal fold immobility includes two broad categories: mechanical fixation and neurogenic paralysis. A mobile arytenoid can be surgically abducted, and this procedure has been reported as a treatment for patients with bilateral neurogenic laryngeal paralysis. This article reviews the theoretical basis and clinical outcomes of this procedure.

RECENT FINDINGS

Two concepts form the theoretical basis for arytenoid abduction. First, in most cases of neurogenic paralysis, laryngeal muscles are not denervated; there is considerable residual or regenerated function of adductor muscles. The vocal fold lies near the midline, because there is inadequate force to abduct the vocal fold. Second, the cricoarytenoid joint is multiaxial. The posterior cricoarytenoid (PCA) muscle rotates the arytenoid about an oblique axis to pull the vocal process laterally and superiorly, while the axis of adduction is nearly vertical. Thus, surgical abduction of the arytenoid, by simulating contraction of the PCA muscle, should not preclude active adduction during phonation or swallow. Surgical arytenoid abduction has been reported to improve the airway in many patients with bilateral laryngeal paralysis, with little or no impairment of vocal function. It is less successful in patients with inspiratory adductor muscle activity, long-term immobility, or previous procedures to statically enlarge the glottis.

SUMMARY

Arytenoid abduction is a promising treatment for selected patients with bilateral neurogenic laryngeal paralysis.

Laryngeal pacing for bilateral vocal fold immobility

PURPOSE OF REVIEW

This article reviews literature on the scientific background of functional electric stimulation of the immobile larynx, the status of animal pacing trials, and first clinical attempts to establish laryngeal pacing.

RECENT FINDINGS

Impaired vocal fold motion is seen following recurrent laryngeal nerve paralysis and is a result of inadequate or synkinetic reinnervation. The term vocal fold paralysis should only be used after verification using laryngeal electromyography. A variety of animal trials give clear evidence supporting the feasibility of laryngeal pacing as a new dynamic approach for the rehabilitation of patients with bilateral vocal fold motion impairment. Laryngeal pacing has become clinically applicable with minimal invasive electrode insertion and newly designed stimulation circuits.

SUMMARY

Laryngeal pacing seems to be on the right path to open up a dynamic rehabilitation of the bilaterally motion-impaired larynx.

Modulation of nerve fibers in the rat thyroarytenoid muscle following recurrent laryngeal nerve injury

CONCLUSION

Regeneration of nerve fibers in the thyroarytenoid (TA) muscle occurred actively after damage on the recurrent laryngeal nerve (RLN) compared with the vagus nerve (VN). However, remyelination did not occur after damage on the RLN.

OBJECTIVES

To determine the regeneration process of nerve fibers in the TA muscle following transection and immediate anastomosis of the RLN or VN.

METHODS

Three types of animal model were prepared: an RLN anastomosis model (RLNa), a VN anastomosis model (VNa), and a peroneal nerve anastomosis model (PNa). Animals were sacrificed at five time points following the procedure. The modulation of axons, myelin sheaths, Schwann cells (SCs), nerve terminals (NTs), and acetylcholine receptors (AchRs) in the TA or tibialis anterior muscles was examined by immunohistochemical analysis. The ratios of the expression areas in axons, myelin sheaths, and SCs, and the number of NTs and AchRs in the treated (T) and untreated (U) sides (T/U) were evaluated.

RESULTS

At 18 weeks, the T/U ratios of expression in RLNa, VNa, and PNa were 68.5, 0, and 100.4%, respectively, in axons; 0, 0, and 97.6% in myelin sheaths; 53.7, 0, and 93.6% in SCs; 61.0, 0, and 96.4% in NTs; and 99.4, 67.0, and 101.2% in AchRs.

Systematic review of laryngeal reinnervation techniques

OBJECTIVE: To systematically review outcomes of reinnervation techniques for the management of unilateral vocal fold paralysis (UVFP).

DATA SOURCES: Medline and Cochrane databases for English-language studies published between 1966 and 2009 on the surgical management of UVFP.

REVIEW METHODS: Studies were excluded if they reported on bilateral vocal fold paralysis, used nonhuman subjects, or did not assess clinical outcomes. Outcomes of interest were visual analysis, acoustic analysis, perceptual analysis, and electromyography.

RESULTS: Of 686 initial studies, 14 studies encompassing 329 patients were eligible for analysis. All studies had a case-series design. Of reported patients, 60.2 percent were men, with mean age of 51 years (range, 12-79 years). The most common reinnervation technique was ansa cervicalis-to-recurrent laryngeal nerve (RLN), which was most commonly performed after thyroidectomy (43.5%). Other techniques with reportable outcomes included primary RLN anastomosis, ansa-to-RLN combined with cricothyroid muscle-nerve-muscle pedicle, ansa-to-thyroarytenoid neural implantation, ansa-to-thyroarytenoid neuromuscular pedicle, and hypoglossal-to-RLN. Median postsurgical follow-up was 12 months, and mean time to first signs of reinnervation was 4.5 months (SD 2.9 months). Visual analysis of glottic gap showed the greatest mean improvement with ansa-to-RLN, from 2.25 (SD 0.886) to 0.75 (SD 0.886) mm ( P < 0.01). Acoustic analysis showed greatest improvement with neural implantation, with a change in mean phonation time from seven (SD 1.22) to 16 (SD 5.52) seconds ( P < 0.01). Perceptual analysis and electromyography demonstrated improvement in all studies.

CONCLUSION: Reinnervation is effective in the management of UVFP, although the specific method may be dictated by anatomical limitations. Prospective studies utilizing uniform and consistent outcome parameters are necessary.

Local neurotoxins for prevention of laryngeal synkinesis after recurrent laryngeal nerve injury

OBJECTIVES

Persistent vocal fold motion impairment after recurrent laryngeal nerve (RLN) injury is not characteristically due to absent reinnervation, but often results from spontaneous aberrant reinnervation (synkinesis). We administered local neurotoxins to selected laryngeal muscles after RLN injury to determine whether aberrant reinnervation could be selectively inhibited.

METHODS

Unilateral RLN transection was performed in 24 male rats. Three weeks later, the denervated laryngeal adductor complex was injected with phenol, high- or low-dose vincristine sulfate (VNC), or saline solution. One month later, rat larynges were evaluated via videolaryngoscopy and laryngeal electromyography (LEMG). Larynges from euthanized animals were analyzed via immunofluorescent staining for the presence of reinnervation.

RESULTS

One animal that received phenol and 3 animals that received high-dose VNC died of toxicity-related complications. In the surviving neurotoxin-treated animals, videolaryngoscopy showed increased lateralization of the immobile vocal fold. Only 1 phenol-injected rat had adductor complex motor recruitment (score of 3+) with LEMG. The other neurotoxin-treated animals demonstrated an absence of adductor complex reinnervation, with only insertional activity and fibrillations (no motor units/recruitment). Spontaneous ipsilateral abductor reinnervation was not affected by the adductor injections.

CONCLUSIONS

Low-dose VNC injections appear to be relatively safe and effective in selectively inhibiting spontaneous aberrant reinnervation after RLN injury in an animal model.

Improvement of respiratory compromise through abductor reinnervation and pacing in a patient with bilateral vocal fold impairment

OBJECTIVES/HYPOTHESIS

To determine whether respiratory compromise from bilateral vocal fold impairment (paralysis) can be objectively alleviated by reinnervation and pacing.

METHODS

A patient with paramedian vocal folds and synkinesis had a tracheotomy for stridor after bilateral laryngeal nerve injury and Miller Fisher syndrome. One posterior cricoarytenoideus (PCA) received a nerve-muscle pedicle fitted with a perineural electrode for pacemaker stimulation. The airway was evaluated endoscopically and by spirometry for up to 1 year.

RESULTS

Bilateral vocal fold patency during quiet breathing was reversed to active vocal fold adduction during tracheal occlusion. Peak inspiratory flows (PIFs) were significantly higher (P < .001) after reinnervation. PIFs and glottic apertures increased further under stimulation (42 Hz, 1-4 mA, 42-400 microsec). although the differences were not significant.

CONCLUSIONS

Based on our preliminary data, PCA reinnervation and pacing offer promise for amelioration of respiratory compromise after paradoxical adduction in bilateral vocal fold impairment.

Unilateral true vocal fold synkinesis presenting with airway obstruction

OBJECTIVES

We present a case series of 10 patients with unilateral true vocal fold paralysis who presented with airway obstruction.

METHODS

A retrospective review of the authors' patients at 2 institutions with unilateral true vocal fold motion impairment was carried out over a 10-year period. Of these, 10 patients were identified who presented with stridor and dyspnea as a result of synkinesis. Six cases were a result of thyroidectomy, 1 case resulted from recurrent laryngeal nerve section for spasmodic dysphonia, 1 case occurred after anterior cervical diskectomy and fusion, and in 2 cases no cause was identified.

RESULTS

Three patients underwent tracheotomy. Two patients underwent partial arytenoidectomy. Seven patients underwent botulinum toxin injection; 2 were treated with breathing therapy, and in 1 case breathing therapy was recommended. Seven patients underwent treatment with more than 1 method.

CONCLUSIONS

Unilateral vocal fold paralysis may present with airway obstruction as a result of synkinesis. Treatment should be incremental and starts with breathing therapy and botulinum toxin injection. Partial arytenoidectomy or tracheotomy may be necessary for refractory cases.

Diagnosis and Prognosis of Iatrogenic Injury of the Recurrent Laryngeal Nerve

Objectives:

Following perioperative injury to a macroscopically intact recurrent laryngeal nerve (RLN), there are two possible intraneural injury types: 1) axonal injury, including disruption of axons, and 2) conduction block, only affecting the Schwann cells and the nodes of Ranvier. In this study, it was hypothesized that the functional outcome after RLN injury may depend on the type of nerve injury.

Methods:

Fifteen patients with acute postoperative unilateral RLN paralysis were prospectively studied. Electrophysiological examination (laryngeal electromyography) was used to differentiate between the two types of nerve injury. Vocal fold motions were monitored by repeated laryngoscopy during the study period (up to 6 months). Three of the patients with axonal injury were treated with the regeneration-promoting agent nimodipine.

Results:

The patients with conduction block all recovered normal vocal fold motion, whereas patients with axonal injury within the nerve had a significantly worse outcome. The 3 patients who were treated with nimodipine all recovered normal or near-normal vocal fold mobility despite the more severe axonal injury.

Conclusions:

In contrast to previous reports, our results show that laryngeal electromyography is a reliable tool for diagnosing the type of injury within the injured RLN, making it possible to predict the functional outcome in these patients. On the basis of the results, a future randomized study on nimodipine treatment for RLN axonal injury is suggested.

Preserved Regeneration and Functional Recovery of the Injured Recurrent Laryngeal Nerve after Secondary Surgical Repair in Adult Rats

Objectives:

Transection of the recurrent laryngeal nerve (RLN) is accompanied by poor functional recovery, despite primary repair, because of regeneration difficulties. Nimodipine can promote regeneration, but it is not yet clear whether preoperative treatment is necessary. It is also not clear whether surgical repair following RLN injury may be performed in a second procedure, with preserved regeneration. This study investigated the time window for secondary surgical repair of the transected RLN and the need for preoperative administration of nimodipine.

Methods:

In adult rats, the left RLN was transected and repaired at time intervals up to 3 weeks after transection, in combination with nimodipine treatment starting either before or after the operation. Regeneration and neuromuscular recovery were assessed by electrophysiology, retrograde tracing, and immunohistochemistry.

Results:

Similar (whether 0, 2, or 7 days) regenerative results were obtained when the RLN was repaired up to 1 week after injury, given nimodipine administration, whereas fewer motor neurons managed to regenerate after nerve repair at 3 weeks after the initial transection. No beneficial effect was detected from preoperative nimodipine administration.

Conclusions:

Provided that nimodipine is administered, surgical reconstruction of the RLN can be performed within 1 week after the initial nerve trauma, with preserved neuromuscular function. Nimodipine may be administered at the time of RLN transection injury.

Vocal fold paresis: evidence and controversies

PURPOSE OF REVIEW

To present and assess the current state of knowledge regarding vocal fold paresis.

RECENT FINDINGS

Neurogenic compromise of vocal fold function exists along a continuum encompassing partial denervation (paresis), complete denervation (paralysis), and variable degrees and patterns of reinnervation. Not abundantly recognized clinically until recently, paresis typically presents with symptoms of glottic insufficiency. As a result of preserved vocal fold mobility, paresis can be difficult to diagnose and to distinguish from innocent vocal fold asymmetry. Laryngoscopy alone has proved an unreliable means of diagnosis, and laryngeal electromyography, although not immune to error itself, is often helpful. Treatment consists of medialization procedures that do not compromise remaining nerve function. Significant disagreement exists regarding the incidence, causes and relationship to other pathologies. In the absence of evidence, natural history must be inferred.

SUMMARY

Vocal fold paresis is probably a significant source of vocal disability, especially among cases that have eluded straightforward diagnosis. An accurate assessment of its clinical impact, patterns of dysfunction, natural history and relationship to other pathologies depends on diagnostic rigor and accuracy and is still evolving.

Surgical treatment of superficial esophageal cancer

OBJECTIVE

The worldwide incidence of superficial esophageal cancer (SEC) is increasing. The aim of this study is to review the systematic surgical outcomes of esophagectomy for SEC.

DATA SOURCES

Only manuscripts written in English and written between 1980 and 2003 were selected from MEDLINE. The keywords consisting of superficial esophageal cancer, early esophageal cancer, and early stage or superficial stage or stage I in esophageal cancer were searched.

STUDY SELECTION

There were no exclusion criteria for published information relevant to the topics. The most representative articles were selected when there were several articles from the same institution. Case reports were excluded. DATA EXTRACTIONS: Thirty-two manuscripts were finally collected from MEDLINE and eight articles were also added from reference lists of the pertinent literatures. In evaluating the statistical analysis of the complications of the reported literature, collective method was used.

DATA SYNTHESIS

The collected information was organized.

CONCLUSIONS

The conclusions drawn from those articles showed that the overall prevalence of SEC accounted around 10% and increased to 25% in the 2000s. The overall incidence of lymph node metastasis of SEC was about 25% and its incidences in mucosal and submucosal cancer were 5 and 35%, respectively. The percentage of the cases of squamous cell carcinoma (SCC) vs adenocarcinoma (AC) widely varied depending on the geographic locations reported; most SCC cases were from the Asian countries and most AC cases were from the European countries. Clinical significance of multimodal treatment for SEC has dramatically developed in the recent era and could provide various potential therapeutic options for SEC. These concepts make it possible to individualize surgical management of SEC as part of various multimodal treatments. The operative approaches for SEC varied from minimally invasive thoracoscopic esophagectomy, limited transabdominal distal esophagectomy, conventional transthoracic esophagectomy, transhiatal esophagectomy without thoracotomy, en bloc esophagectomy, and to extended esophagectomy with a complete three-field lymph node dissection. A 5-year overall survival rate of SEC after esophagectomy was good (46 to 83%) to excellent (71 and 100%) for mucosal SEC, but far from satisfactory (33 and 78%) for submucosal SEC. Early diagnosis, development of multimodal treatment, standardization of the surgical procedure including routine lymph node dissection, and improved perioperative management of patients have led to a better survival for patients with SEC.

Anesthetic considerations in the multiple endocrine neoplasia syndromes

PURPOSE OF REVIEW

The multiple endocrine neoplasia (MEN) syndromes present a diverse array of challenges to the anesthesiologist. The tumors and their effects are often underdiagnosed and potentially discovered only when the patient is undergoing surgery for either a component of one of the syndromes or another procedure altogether. This can present the anesthesiologist with a life-threatening situation in the operating room. A thorough understanding of the syndromes, as well as management strategies, will enable the anesthesiologist to handle these patients.

RECENT FINDINGS

Advances in the pharmacologic armamentarium available to physicians have enabled patients with MEN, particularly those with the carcinoid syndrome or pheochromocytoma, to undergo surgery safely, with minimal morbidity and mortality.

SUMMARY

Awareness of the components of the MEN syndromes, as well as careful preoperative preparation, paves the way for a smooth anesthetic and postoperative course in these patients.

Diagnostic tools in laryngology

PURPOSE OF REVIEW

Laryngology has become recognized as a subspecialty within the field of otolaryngology-head and neck surgery over the course of the past 30 years. The evolution of laryngology stems primarily from our better understanding of the physiology of vocal production, society's increased reliance on oral communication in industry, and the resultant demand for improvements in diagnostic and therapeutic protocols to enhance vocal performance. The purpose of this review is to describe current advances in diagnostic tools in laryngology that contribute to our understanding of vocal physiology and our ability to improve quality of life as it relates to vocal performance.

RECENT FINDINGS

Diagnostic tools in laryngology allow the clinician the ability to assess the vibratory function of the vocal folds, evaluate laryngeal structure and airway patency, assess glottal and pulmonary airflow, assess the neurologic integrity of the vocal folds, analyze the quality of the voice signal, and assess the degree of functional disability as it relates to laryngeal pathology.

SUMMARY

Primary advances in diagnostic laryngology include improvements in laryngoscopy techniques, imaging, electromyography, aerodynamic testing, acoustic analysis, and functional assessment, each of which is improving our ability to understand, diagnose, and treat a wider spectrum of voice, airway, and swallowing disorders.