Practice Parameter: Laryngeal Electromyography (An Evidence-Based Review)

Laryngeal Surgery as It Pertains to the Thoracic Surgeon

A surgeon managing complex airway disease benefits from knowledge of laryngeal physiology and pathology. The Larynx provides phonation and protection for the lower airway via closure and cough reflex. Disruption of these functions or development of paralysis or stenosis can lead to respiratory failure. Management includes a variety of endoscopic and open management techniques. Understanding of laryngeal physiology can also limit laryngeal functional impairment through careful preservation of motor nerves and early recognition of injuries.

Laryngeal Electromyography in the Therapeutic Process of Patients with Vocal Fold Immobility or Dysmobility

(1) Background: Laryngeal electromyography (LEMG) plays a key role in classifying the severity of nerve damage and determining the prognosis of the nerve recovery. LEMG is primarily a qualitative study, without a standardized approach to interpretation. The development of qualitative and quantitative analysis would situate LEMG in the gold standard of modern neurolaryngologic diagnostics. The aim of this study was to quantitatively evaluate laryngeal electromyography recorded in patients with vocal fold immobility or dysmobility. (2) Methods: The electromyographic material comprised 84 thyroarytenoid muscles recordings of 42 patients. (3) Results: In our study, we observed significant differences between EMG characteristics of healthy and paralyzed VF. Our study showed that recording laryngeal muscle activity during successive phases of breathing provides additional valuable information. We noticed that the frequency and amplitude of motor unit potentials correlates with the return of vocal fold functionality. (4) Conclusions: Laryngeal EMG guides the clinician on the best course of treatment for the patient. It is therefore important to develop an effective methodology and consensus on the quantitative interpretation of the record. Amplitude and frequency parameters are valuable in predicting neural recovery and in the return of vocal fold mobility.

The Poor Validity of Asymmetric Laryngoscopic Findings in Predicting Laterality in Vocal Fold Paresis

OBJECTIVE

To determine the laryngoscopic findings most predictive of laterality in vocal fold paresis in patients with known RLN and/or SLN paresis by laryngeal electromyography (LEMG).

STUDY DESIGN

Blinded, prospective video perceptual analysis study.

METHODS

Patients with vocal fold paresis diagnosed by LEMG at a tertiary care hospital from 2017 to 2019 were identified. Two fellowship-trained laryngologists blinded to clinical history and LEMG results reviewed laryngostroboscopic examinations and assessed for evidence of paresis using defined criteria. Inclusion criteria were adults with laryngeal asymmetry and evidence of decreased recruitment on LEMG. Exclusion criteria were children, presence of laryngeal lesions, myasthenia gravis, vocal fold paralysis, and normal laryngeal symmetry.

RESULTS

We identified 95 patients who were diagnosed with vocal fold paresis with LEMG who met inclusion and exclusion criteria (mean age 43.8 ± 20.4 years (18-88), 38.9% male). When comparing the laterality of the observed laryngoscopic finding with LEMG, we found that in patients who had severe true vocal fold (TVF) range of motion disturbance, the laterality of the finding matched the LEMG distribution of paresis in 12 out of 13 (92.3%) patients (P = 0.002). No other laryngoscopic findings reliably predicted laterality including corniculate and cuneiform cartilage asymmetry, pyriform sinus dilation, abnormal TVF show, petiole deviation, abnormal ventricular show, increased supraglottic area, and FVF hyperfunction of the opposite side.

CONCLUSION

With the exception of severe TVF range of motion disturbance, there seems to be poor validity of laryngoscopic findings in predicting the affected side in vocal fold paresis. We recommend neurophysiologic testing to confirm the clinical diagnosis of vocal fold paresis.

Study on Normal Laryngeal Electromyography of Thyroarytenoid Muscle, Cricothyroid Muscle, and Posterior Cricoarytenoid Muscle

OBJECTIVE

The aim of this study was to investigate the physiological activity of intrinsic laryngeal muscle under different functional states of larynx by measuring the normal laryngeal electromyography parameters.

METHODS

Laryngeal electromyography (EMG) was performed in 112 patients with unilateral vocal cord movement disorder. The duration and amplitude of the motor unit potential (MUP) of the thyroarytenoid muscle (TA), posterior cricoarytenoid muscle (PCA), and cricothyroid muscle (CT) were measured when patients were asked to make a deep inspiration and phonate /i/. The normal side of the patients' vocal chords was used as the research object.

RESULTS

(1) The motor unit potential of TA, CT, and PCA were measured when inspiration and phonating /i/. Waveforms were normal. (2) There were significant differences in duration of TA between inspiration and phonating /i/ in comfortable tone. (3) When comparing the duration and amplitude of any 2 of TA, CT, and PCA during inspiration and phonating /i/, there were significant differences in duration between CT and PCA when phonating /i/ only. There were no significant differences in any other comparisons.

CONCLUSIONS

Under either deep inspiration or pronunciation, the TA, CT, and PCA muscles were activated. The TA may play a major role in phonating. The PCA may play a major role in the action of deep inspiration.

[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.

Hemodynamic stability during laryngeal electromyography procedures

BACKGROUND

Laryngeal electromyography (LEMG) is accepted as safe, with minimal side effects. However, patient hemodynamic stability, during these procedures, has not been reported. This study aimed to investigate the hemodynamics in patients undergoing LEMG and determine the risk factors for hemodynamic changes.

METHODS

We recruited 89 consecutive patients who underwent LEMG. Baseline and postprocedural changes in vital signs were analyzed.

RESULTS

Diastolic blood pressure (DBP) increased from 75.08 ± 11.54 mmHg preprocedure to 77.4 ± 11.91 mmHg postprocedure (p = .006); pulse rate (PR) increased from 78.1 ± 13.3 beats per minute preprocedure to 80.02 ± 13.69 postprocedure (p = .027). Systolic blood pressure (SBP) and oxygen saturation were unchanged after the procedure. However, about 17% of patients experienced profound changes in vital signs of >20% above baseline during LEMG. The hemodynamic changes did not differ between sexes or between surgical and non-surgical etiologies of vocal fold paralysis. Two patients experienced profound but reversible near-syncope during the procedure.

CONCLUSIONS

LEMG is a safe procedure with few immediate complications, though it may affect the patient's hemodynamic status by increasing DBP and PR. The hemodynamic monitoring is recommended so that timely intervention can be applied in case any warning sign occurs.

Spasmodic Dysphonia: A Review. Part 2: Characterization of Pathophysiology

Objective

The purpose of this review is to describe the recent advances in characterizing spasmodic dysphonia. Spasmodic dysphonia is a task-specific focal laryngeal dystonia characterized by irregular and uncontrolled voice breaks. The pathophysiology is poorly understood, and there are diagnostic difficulties.

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).

Conclusion

The diagnosis of spasmodic dysphonia can be difficult due to the lack of a scientific consensus on diagnostic criteria and the fact that other voice disorders may present similarly. Confusion can arise between spasmodic dysphonia and muscle tension dysphonia. Spasmodic dysphonia symptoms are tied to particular speech sounds, whereas muscle tension dysphonia is not. With the advent of more widespread use of high-speed laryngoscopy and videokymography, measures of the disruptions in phonation and delays in the onset of vocal fold vibration after vocal fold closure can be quantified. Recent technological developments have expanded our understanding of the pathophysiology of spasmodic dysphonia.

Implications for Practice

A 3-tiered approach, involving a questionnaire, followed by speech assessment and nasolaryngoscopy is the most widely accepted method for making the diagnosis in most cases. More experimental and invasive techniques such as electromyography and neuroimaging have been explored to further characterize spasmodic dysphonia and aid in diagnosing difficult cases.

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.

Multi-Motor Unit Potential Analysis and Other Quantitative Techniques for Laryngeal Electromyogram

Reference values for motor unit potentials of laryngeal muscles, the thyroarytenoid (TA) and cricothyroid (CT) muscles, have been collected using multi-motor unit potential quantitative electromyogram analysis technique with concentric quantitative electromyogram-needle electrode type in 40 healthy volunteers. The method is well tolerated, easy to perform, and examination of one muscle takes usually around 5 minutes. The mean motor unit potential amplitude of both muscles was significantly larger in men than in women. The method can safely be used in clinical routine. Other quantitative electromyogram methods are also shortly reviewed.

Refractory Dysphonia Due to Isolated Cricothyroid Muscle Dystonia

OBJECTIVE

To demonstrate the utility of electromyography (EMG) in the evaluation and management of treatment-resistant dysphonia.

METHOD

We report a case of refractory dysphonia in which EMG was used to identify and treat isolated cricothyroid (CT) dystonia.

RESULTS

The patient, a healthy 43-year-old woman, presented with 9 months of progressive hoarseness. Her symptoms were present across vocal tasks but were particularly bothersome while dictating. On presentation, her voice was rated grade 3, roughness 3, breathiness 1, asthenia 0, and strain 3 (G3R3B1A0S3). Videostroboscopy was remarkable for hyperfunction. Voice therapy was not beneficial despite appropriate effort. Microdirect laryngoscopy revealed no evidence of structural pathology. The patient was referred for EMG because of her normal examination and failure to improve with therapy. The CT muscle demonstrated an increased latency of 750 ms in all vocal tasks. One month after CT injection with 3 units of botulinum toxin (BTX), her voice was improved. Perceptual voice evaluation was rated G1R1B0A0S1. Voice Handicap Index improved from 87 to 35.

CONCLUSIONS

In the absence of structural pathology, EMG can be a useful adjunct in the diagnosis of dysphonia that persists despite adequate trials of voice therapy. To our knowledge, this is the only report of laryngeal dystonia due to isolated CT dysfunction successfully treated with BTX.

Role of Laryngeal Electromyography in Predicting Recovery After Vocal Fold Paralysis

Accurate prognostication of the outcome of vocal fold immobility assumes great importance in the management. This study aimed to evaluate the prognostic efficacy of Laryngeal electromyography in cases of vocal fold immobility. A nonrandomized prospective study was carried out from Sep 2009 to Jun 2011. Patients were evaluated using Fiberoptic laryngoscopy and Laryngeal electromyography over a period of 24 weeks. 51 subjects participated in the study, comprised of 22 males and 29 females. All patients underwent detailed clinical examination including Fiberoptic laryngoscopy on the first visit and Laryngeal electromyography testing on the second visit. Subsequent neuromonitoring was carried out at 04, 12 and 24 weeks from date of initial recording. Outcome measures of vocal fold motion were dichotomized into persistent vocal fold immobility (unilateral or bilateral) or resolved vocal fold motion (normal). Approximately 24 weeks after onset of palsy, mobility of the paralyzed vocal cord was restored in 31 (60.78 %) of 51 cases, while 20 (39.22 %) remained immobile. Sensitivity of laryngeal electromyography was 92.53 % ; specificity 93.33 %, positive predictive value 98.77 % and negative predictive value 68.29 %. This study confirmed the utility of Laryngeal electromyography in predicting prognosis for recovery of vocal fold motion after laryngeal nerve injury. The results supported the hypothesis that Laryngeal electromyography data can be used effectively to determine a prognosis for recovery of vocal fold motion.

Laryngeal electromyography-guided hyaluronic acid vocal fold injection for unilateral vocal fold paralysis--preliminary results

OBJECTIVES

The purpose of this study is to investigate the feasibility of using an injectable needle electrode to guide hyaluronic acid (HA) vocal fold injection (VFI) during laryngeal electromyography (LEMG) for unilateral vocal fold paralysis (UVFP).

STUDY DESIGN

Prospective study.

METHODS

From March to June 2010, 20 UVFP patients received LEMG examination at our clinic. Before completion of LEMG, 1.0 cc of HA (Restylane Perlane(®); Q-Med, Uppsala, Sweden) was injected via a 26-gauge monopolar injectable needle electrode into paralyzed thyroarytenoid muscle. After injection, 20 patients completed 3-months follow-up and 16 patients completed 6-months follow-up. The data before, 1 week, 3 months, and 6 months after injection, including the normalized glottal gap area (NGGA) from videostroboscopy, maximal phonation time (MPT), mean airflow rate (MAFR), phonation quotient (PQ), perceptual evaluation of voice (grade, roughness, breathiness, asthenia, strain [GRBAS] scale), Voice Handicap Index (VHI), and self-grading of choking (grade 1-7), were analyzed by the Wilcoxon signed rank test.

RESULTS

All of the patients completed the procedure without complications. After injection, mean NGGA was significantly reduced from 8.28 units to 0.52 units (1 week), 1.79 units (3 months), and 1.36 units (6 months). The mean MPT was prolonged from 5.66 seconds to 11.73, 11.25, and 11.93 seconds, respectively. VHI was reduced from 76.05 to 38.10, 37.40 and 35.00, respectively. Other analyzed data (PQ, MAFR, GRBAS scale, and choking severity) also showed statistically significant improvement.

CONCLUSION

LEMG-guided HA VFI provides UVFP patients with neuromuscular function evaluation and treatment in one step. This clinical technique is feasible, and the short-term results are satisfactory.

Surgical treatment of dysphagia

The role of surgery in the management of dysphagia is clear in some areas and controversial in others. Evaluation for the causes of dysphagia can elucidate conditions in which surgery can improve safety, quality of life, or both. Surgical therapy, when indicated, is safe and effective for many causes of dysphagia. This article includes a general overview of the causes of dysphagia that can be addressed successfully with surgery as well as a discussion of why surgery may be less appropriate for other conditions associated with dysphagia.

Diagnostic Testing for Vocal Fold Paralysis: Survey of Practice and Evidence-Based Medicine Review

OBJECTIVES/HYPOTHESIS

Vocal fold paralysis continues to be a dominant topic in laryngology. Although the majority of cases can be attributed to a known etiology, a significant number of patients present without a clear precipitating event. Over 1,500 studies regarding vocal fold paralysis exist in the medical literature, although only a small percentage report on the use of serum or radiographic testing for the evaluation of idiopathic paralysis. Despite this, patients are routinely subjected to diagnostic evaluation to investigate the underlying cause. To characterize contemporary practice, a national survey of the American Broncho-Esophagological Association (ABEA) membership was undertaken. It is hypothesized that the current practice of diagnostic testing for idiopathic vocal fold paralysis is not well supported by an evidence-based medicine (EBM) review of the available medical literature.

STUDY DESIGN

The authors conducted a national survey, systematic EBM review of existing literature.

METHODS

Surveys were mailed to all active ABEA members; responses regarding practice specialization as well as serum/radiographic diagnostic preferences for idiopathic vocal fold paralysis were tabulated and subjected to statistical analysis. To compare contemporary practice with evidence in the available literature, an EBM review was first performed. Articles for evaluation were selected from a Medline search of English-language abstracts related to adult vocal fold paralysis. The publications were individually reviewed and an EBM level and grade were assigned and compared with the survey results.

RESULTS

Eighty-four of 249 active members responded with 76 (31%) replies submitted for analysis. Specific serum tests were advocated by 41 of 76 (54%) respondents, although the majority (52 of 65 [80%]) felt that they were only "occasionally" or "never" necessary. The most common tests were rheumatoid factor (38%), Lyme titer (36%), erythrocyte sedimentation rate (34%), and antinuclear antibody (33%). Fifty-one of 71(72%) felt that computed tomography (CT) was "always" or "often" necessary and 50 of 72 (69%) replied that chest radiography (CXR) was "always" or "often" necessary. There was no significant difference between CT and CXR ordering (P < .51). In contrast, magnetic resonance imaging (MRI) was described as "always" or "often" necessary in 28 of 71 (39%) of the surveys, significantly less than CT (P < .0001). There was no statistical impact of practice specialization on ordering of serum tests (P = .25) or imaging (P = .50 for CT; P = .46 for CXR; P = .45 for MRI). Following analysis of 1,510 vocal fold paralysis abstracts, 19 publications were found to be appropriate for an EBM review of serum testing with 15 available for review of radiographic imaging. Only one study presented level III evidence; the remainder were levels IV and V comprised of retrospective series and case reports. The evidence supporting serum or radiographic testing toward the evaluation of idiopathic vocal fold paralysis is given an overall grade of "C."

CONCLUSIONS

Serum and radiographic testing for the evaluation of vocal fold paralysis is supported by grade "C" evidence only. There are no existing prospective studies estimating the clinical impact of testing on diagnosis or patient outcome. Current practice, as estimated by a survey of the ABEA membership, is not well founded for serum testing and only by retrospective case series with regard to imaging. Further study into the nature of idiopathic vocal fold paralysis and outcomes assessment of diagnostic paradigms may improve clinical practice.