Treatment of the interarytenoid muscle with botulinum toxin for laryngeal dystonia

Botulinum Neurotoxin Therapy in the Clinical Management of Laryngeal Dystonia

Laryngeal dystonia (LD), or spasmodic dysphonia (SD), is a chronic, task-specific, focal movement disorder affecting the larynx. It interferes primarily with the essential functions of phonation and speech. LD affects patients' ability to communicate effectively and significantly diminishes their quality of life. Botulinum neurotoxin was first used as a therapeutic agent in the treatment of LD four decades ago and remains the standard of care for the treatment of LD. This article provides an overview of the clinical application of botulinum neurotoxin in the management of LD, focusing on the classification for this disorder, its pathophysiology, clinical assessment and diagnosis, the role of laryngeal electromyography and a summary of therapeutic injection techniques, including a comprehensive description of various procedural approaches, recommendations for injection sites and dosage considerations.

Respiratory Laryngeal Dystonia: Characterization and Diagnosis of a Rare Neurogenic Disorder

OBJECTIVES/HYPOTHESIS

Respiratory laryngeal dystonia (RLD) is poorly understood and rarely reported in the literature. Patients have atypical laryngeal movement resulting in airway obstruction. This motion is neurogenic in nature, is constant while awake, nonepisodic, and non-trigger dependent. Given its rarity, it is often misdiagnosed for inducible laryngeal obstruction; however, it is refractory to medical and behavioral management. Although this condition has been addressed in the literature, this report is the largest case series characterizing presenting symptomology, multimodal treatment outcomes, and longitudinal course of these patients, and proposes a set of diagnostic criteria to aid in clinical identification of RLD patients. Our objectives were to characterize RLD clinically and offer diagnostic guidelines to clinicians.

STUDY DESIGN

A prospective case series with a retrospective analysis at a tertiary referral center.

METHODS

A review of clinical records and videostroboscopic analysis of 16 patients treated for respiratory laryngeal dystonia from October 2005 to October 2018 was performed.

RESULTS

Sixteen patients with respiratory laryngeal dystonia were included. The common features of this group were persistent, nonepisodic dyspnea and stridor with laryngoscopic evidence of paradoxical vocal fold motion. Our patients had no structural neurologic abnormalities. These patients typically failed respiratory retraining therapy and medical management of laryngeal irritants. In our series, 100% of patients underwent respiratory retraining therapy, 68.8% received laryngeal botulinum toxin injection, and 31.3% required tracheostomy.

CONCLUSIONS

RLD is a rare and challenging condition. The disorder can be severely disabling, and treatment options appear limited. A multidisciplinary approach may be helpful. Some patients responded to laryngeal botulinum injection and medical management, whereas others required tracheostomy for symptom control. Laryngoscope, 2020.

Interarytenoid botulinum toxin A injection for the treatment of vocal process granuloma

OBJECTIVES

To report on the efficacy and adverse effects of interarytenoid botulinum toxin A injection for the treatment of vocal process granuloma.

METHODS

A retrospective chart review was conducted of eight patients with vocal process granuloma resistant to anti-reflux therapy who underwent interarytenoid botulinum toxin A injection. The mean dosage of botulinum toxin A injected was 6.56 U.

RESULTS

Fifty per cent of patients had complete regression of the lesion and 50 per cent had partial regression. The main side effects were breathiness (n = 4), voice breaks (n = 1) and aspiration (n = 1).

CONCLUSION

Interarytenoid botulinum toxin A injection for the treatment of vocal process granuloma is an effective mode of therapy, with transient vocal and swallowing side effects.

Movement Disorders and Voice

The primary movement disorders affecting the voice are laryngeal dystonia (including spasmodic dysphonia), essential voice tremor, and Parkinson disease. Diagnosis of these conditions is clinical and based on a detailed history, voice evaluation, and physical and laryngoscopic examination. Laryngeal dystonia and essential voice tremor are hyperfunctional disorders and are treated most commonly with botulinum toxin injections. Parkinson disease is a hypofunctional disorder that may affect the voice and most commonly is treated with Lee Silverman Voice Treatment.

Chemodenervation of the Larynx

Botulinum neurotoxin (BoNT) has existed for thousands of years; however, it was not medically utilized until investigations into its therapeutic use began in sincerity during the late 1970s and 1980s. This, coupled with the reclassification of spasmodic dysphonia as a focal dystonia, led to the use of chemodenervation for this disorder, which has since become a refined technique. Indeed, due to its safety and efficacy, BoNT has been investigated in multiple neurolaryngology disorders, including spasmodic dysphonia, vocal tremor, and muscle tension dysphonia. BoNT has been shown to be a useful and safe adjunct in the treatment for these disorders and may reduce or eliminate oral pharmacotherapy and/or prevent the need for a surgical intervention. We present the historical background, development, proposed mechanisms of action, uses, and techniques for administering BoNT for laryngeal disorders, with a particular focus on spasmodic dysphonia.

Findings of Multiple Muscle Involvement in a Study of 214 Patients with Laryngeal Dystonia Using Fine-Wire Electromyography

Although perceptual and stroboscopic data help in diagnosing and classifying laryngeal dystonia, these measures do not aid the voice clinician in targeting which specific muscles to treat with botulinum toxin. Most patients achieve smoother, less effortful voicing with standard injection regimens. However, there is a notable failure rate. We performed fine-wire electromyography on 214 consecutive patients with laryngeal dystonia. We correlated voice ratings, stroboscopy data, and fine-wire electromyography data. Videostroboscopy was successful in visually demonstrating most of the audible findings in isolated vocal tremor, but it was much less successful in identifying breaks alone or a combination of breaks and tremor. Fine-wire electromyography revealed that the thyroarytenoid muscle was significantly more likely than the lateral cricoarytenoid muscle to be the predominant muscle associated with adductor spasmodic dysphonia, and that the thyroarytenoid and lateral cricoarytenoid muscles were equally likely to be predominantly involved in tremor spasmodic dysphonia. In addition, several patients in both the adductor spasmodic dysphonia and the tremor spasmodic dysphonia groups presented with interarytenoid muscle predominance. All of the intrinsic laryngeal muscles are capable of being the predominant muscle in laryngeal dystonia, and there are patterns of muscle abnormalities that differ between adductor spasmodic dysphonia and tremor spasmodic dysphonia. Some of the failures in treating adductor spasmodic dysphonia with botulinum toxin, and the greater difficulty with success in treating patients with tremor spasmodic dysphonia, are due to failure to deliver toxin to the appropriate muscles.

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.

Effect on laryngeal adductor function of vincristine block of posterior cricoarytenoid muscle 3 to 5 months after recurrent laryngeal nerve injury

OBJECTIVES

It has been shown in a canine model that a single injection of vincristine into the posterior cricoarytenoid (PCA) muscle at the time of recurrent laryngeal nerve (RLN) injury effectively blocks its reinnervation and results in improved adductor strength. But clinically, such injuries are usually diagnosed weeks or months after onset. Vincristine injection does not affect a muscle that is already innervated; thus, there is a limited time frame following RLN injury during which a vincristine injection could effectively improve ultimate laryngeal adductor functional recovery. A series of delayed injections was performed in a canine model and results assessed.

STUDY DESIGN

Animal (canine) experiment.

METHODS

The RLN was transected and repaired, and vincristine (0.4 mg) was injected into the PCA muscle at the time of injury (n=12) or 3, 4, and 5 months later (n=8 each study group). Six months after RLN injury, laryngeal adductor function was measured. Results of vincristine injection without RLN injury (n=6) and longer-term (12 months) follow-up for time zero injections (n=4) are also reported.

RESULTS

The animals injected at time zero had better adductor function than non-injected controls, as reported previously, and this result was further increased at 12 months. The 3-month delay gave results similar to the time zero group. The 5-month delay group showed no vincristine benefit, and the 4-month delay group gave an intermediate result. Vincristine to the PCA had no effect on adductor function when the RLN was left intact. Plasma levels showed 19% of injected vincristine reached systemic circulation, which was cleared within 69 hours.

CONCLUSIONS

Vincristine injection of the PCA muscle after RLN injury, which blocks this antagonist muscle from synkinetic reinnervation, leads to improved laryngeal adductor functional recovery. The window of opportunity to apply this treatment closes by 4 months after RLN injury in the canine model. Human RLN recovery follows a similar time course and can reasonably be expected to have a similar therapeutic window.

Recommendations of the Neurolaryngology Study Group on laryngeal electromyography

The Neurolaryngology Study Group convened a multidisciplinary panel of experts in neuromuscular physiology, electromyography, physical medicine and rehabilitation, neurology, and laryngology to meet with interested members from the American Academy of Otolaryngology Head and Neck Surgery, the Neurolaryngology Subcommittee and the Neurolaryngology Study Group to address the use of laryngeal electromyography (LEMG) for electrodiagnosis of laryngeal disorders. The panel addressed the use of LEMG for: 1) diagnosis of vocal fold paresis, 2) best practice application of equipment and techniques for LEMG, 3) estimation of time of injury and prediction of recovery of neural injuries, 4) diagnosis of neuromuscular diseases of the laryngeal muscles, and, 5) differentiation between central nervous system and behaviorally based laryngeal disorders. The panel also addressed establishing standardized techniques and methods for future assessment of LEMG sensitivity, specificity and reliability for identification, assessment and prognosis of neurolaryngeal disorders. Previously an evidence-based review of the clinical utility of LEMG published in 2004 only found evidence supported that LEMG was possibly useful for guiding injections of botulinum toxin into the laryngeal muscles. An updated traditional/narrative literature review and expert opinions were used to direct discussion and format conclusions. In current clinical practice, LEMG is a qualitative and not a quantitative examination. Specific recommendations were made to standardize electrode types, muscles to be sampled, sampling techniques, and reporting requirements. Prospective studies are needed to determine the clinical utility of LEMG. Use of the standardized methods and reporting will support future studies correlating electro-diagnostic findings with voice and upper airway function.

Long-Term Follow-Up Results of Selective Laryngeal Adductor Denervation-Reinnervation Surgery for Adductor Spasmodic Dysphonia

Selective laryngeal adductor denervation-reinnervation surgery for the treatment of adductor spasmodic dysphonia was reported in 1999 in 21 patients with encouraging results. Here, we report long-term results of this procedure. Surgical outcome was evaluated using patient surveys and perceptual voice assessment. Measured outcomes included Voice Handicap Index (VHI)-10 scores, patient questionnaire, and perceptual evaluation for voice breaks and breathiness. Patient survey was obtained from 83 patients, and perceptual voice evaluation was performed in voice samples from 46 patients. Average follow-up interval was 49 months. Mean VHI-10 scores improved from a mean of 35.6 to 12.7. Eighty-three percent showed significantly improved VHI-10 scores, representing improved physical, social, and emotional well-being. There was a high degree of patient satisfaction, with 91% agreeing that their voice is more fluent after the surgery. Perceptual evaluation of postoperative voice samples revealed voice breaks in 26% (15% mild, 4% moderate, 7% severe) and breathiness in 30% (11% mild, 13% moderate, 6% severe). A majority of patients had stable, long-lasting resolution of spasmodic voice breaks.