Unilateral versus bilateral thyroarytenoid Botulinum toxin injections in adductor spasmodic dysphonia: a prospective study

Comparison of the efficacy and adverse effects of unilateral or bilateral botulinum toxin injections for adductor spasmodic dysphonia: a systematic review and meta-analysis

PURPOSE

This study aims to aggregate and analyze existing clinical evidence to compare the efficacy and adverse effects of unilateral or bilateral botulinum toxin injections for the treatment of adductor spasmodic dysphonia (ADSD).

METHODS

Reports from non-randomized controlled trials and cohort studies pertaining to the efficacy and adverse effects of unilateral and bilateral botulinum toxin injections for ADSD were identified and retrieved from four electronic databases from inception to July 2023. The meta-analysis employed fixed or random effects models to assess pooled relative risks (RR), mean differences (MDs), and standard mean differences (SMDs) with their corresponding 95% confidence intervals (CIs).

RESULTS

We included two non-randomized controlled trials and seven cohort studies comprising 854 total patients. Meta-analysis of the included studies showed that bilateral botulinum toxin injections associated with a longer duration of vocal improvement (MD =  - 2.89, 95% CI - 3.13 to - 2.65, I2 = 0%, P < 0.00001). However, bilateral botulinum toxin injections associated with an increase in adverse effects, including a longer duration of breathy voice quality (SMD =  - 0.51, 95% CI - 0.79 to - 0.22, I2 = 35%, P = 0.0005) and a higher occurrence of swallowing difficulties (RR = 0.46, 95% CI 0.35 to 0.11, I2 = 0%, P < 0.00001).

CONCLUSION

Bilateral botulinum toxin injections for ADSD showed a longer duration of vocal improvement, a longer breathy voice duration and a higher dysphagia occurrence and duration than unilateral injections.

Improved vocal quality and decreased vocal effort after botulinum toxin treatment for laryngeal dystonia

OBJECTIVES

Laryngeal dystonia (LD) is characterized by irregular and involuntary task-specific spasms of the intrinsic laryngeal muscles. There is no curative treatment for it, however, laryngeal botulinum neurotoxin injections (BoNT-I) are considered the standard of care therapy. This study aims to characterize the population of LD patients and to assess the results of laryngeal BoNT-I.

METHODS

A Retrospective cohort study was conducted. Medical records were reviewed for all the patients with LD diagnosis seen in the Voice Unit of the Red de Salud UCChristus between January 2013 and October 2021. Biodemographic, clinical and treatment data were collected. Additionally, a telephonic survey was completed by the patients that underwent laryngeal BoNT-I, including self-reported voice outcomes and Voice Handicap Index 10 (VHI-10).

RESULTS

Of the 34 patients with LD included in the study, 23 received a total of 93 laryngeal BoNT-I and 19 completed the telephone survey. The majority (97%) of the injections corresponded to patients with adductor LD and 3% to abductor LD. Patients received a median of 3 (1-17) injections, with a more frequent cricothyroid approach (94.4%), while the thyrohyoid approach accounted for 5.6% of cases. Most injections were bilateral (96.8%). A significant improvement in the vocal quality and effort was noted after the last injection and the overall BoNT-I treatment (P < 0.001). Similarly, the VHI-10 score improved from a median of 31 (7-40) to 2 (0-19) (P < 0.001) after the last injection. A post-treatment breathy voice was reported in 95% of patients, and dysphagia to liquids and solids in 68% and 21%, respectively.

CONCLUSIONS

Laryngeal BoNT-I is an effective treatment for LD, achieving an improvement in self-reported vocal quality and VHI-10 scores, and a reduction of the self-reported vocal effort. Adverse effects are mild in the majority of cases, constituting a safe and effective therapy for these patients.

Guidelines for the Use of Botulinum Toxin in Otolaryngology From the Korean Society of Laryngology, Phoniatrics and Logopedics Guideline Task Force

The Korean Society of Laryngology, Phoniatrics and Logopedics created a task force to establish clinical practice guidelines for the use of botulinum toxin (BT) in otolaryngology. We selected 10 disease categories: spasmodic dysphonia, essential vocal tremor, vocal fold granuloma, bilateral vocal fold paralysis, Frey's syndrome, sialocele, sialorrhea, cricopharyngeal dysfunction, chronic sialadenitis, and first bite syndrome. To retrieve all relevant papers, we searched the CORE databases with predefined search strategies, including Medline (PubMed), Embase, the Cochrane Library, and KoreaMed. The committee reported 13 final recommendations with detailed evidence profiles. The guidelines are primarily aimed at all clinicians applying BT to the head and neck area. In addition, the guidelines aim to promote an improved understanding of the safe and effective use of BT by policymakers and counselors, as well as in patients scheduled to receive BT injections.

Botulinum Toxin Therapy for Spasmodic Dysphonia in Japan: The History and an Update

Spasmodic dysphonia (SD) is a rare neurological disorder that impairs phonatory function by triggering involuntary and intermittent contractions of the intrinsic laryngeal muscles. SD is classified into three types: adductor SD (AdSD), abductor SD (AbSD), and mixed SD. Of these, AdSD accounts for 90–95% of disease; younger females are predominantly affected. Botulinum toxin injection into the laryngeal muscles is safe, minimally invasive, and very effective. Here, we review the history of clinical research for SD conducted in Japan. The first use of botulinum toxin injection therapy to treat SD in Japan was by Kobayashi et al. in 1989. The group developed an objective mora (syllable) method to evaluate SD severity. Recently, we conducted a placebo-controlled, randomized, double-blinded clinical trial of botulinum toxin therapy for AdSD and an open-label trial for AbSD to obtain the approval of such therapy by the Japanese medical insurance system. The mora method revealed significant voice improvement and the evidence was of high quality. Additionally, a clinical trial of type 2 thyroplasty using titanium bridges confirmed the efficacy and safety of such therapy. These studies broadened the SD treatment options and have significantly benefited patients.

Alternating Unilateral Versus Bilateral Injections of Botulinum Toxin for the Treatment of Adductor Spasmodic Dysphonia

OBJECTIVE

This study aimed to compare the long-term efficacy, durability, and dose and interval stability between alternating unilateral and bilateral injections of botulinum neurotoxin type A for the treatment of adductor spasmodic dysphonia.

STUDY DESIGN

Retrospective cohort study.

SETTING

Academic tertiary medical center.

METHODS

A total of 137 patients (105 alternating unilateral and 32 bilateral injections) who were administered ≥5 injections of botulinum neurotoxin type A were included in this study. The mean dosage change, dose adjustment ratio (number of dose increases/total number of injections), and stability of treatment responses were compared between the alternating unilateral and bilateral injection groups.

RESULTS

Long-term changes in the mean dosages for alternating unilateral (mean ± SD, -0.010 ± 0.048 IU) and bilateral (-0.042 ± 0.142 IU) injections did not differ between groups (P = .225), suggesting that both methods follow a decreasing dosing trend over time. The dose adjustment ratio also did not differ between groups (P = .077), although a longer average treatment interval (P < .001) and duration of hoarse voice (P = .045) were found in the bilateral injection group. The proportion of stable patients who did not increase injection dose and had regular follow-up did not differ between the groups.

CONCLUSION

Both alternating unilateral and bilateral injection methods showed a long-term decreasing dosing trend, with comparable levels of efficacy, durability, and stability for treating adductor spasmodic dysphonia. Our findings indicate that alternating unilateral injections can be routinely performed with fewer side effects, albeit at shorter treatment intervals, than bilateral injections.

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.

Botulinum toxin A, brain and pain

Botulinum neurotoxin type A (BoNT/A) is one of the most potent toxins known and a potential biological threat. At the same time, it is among the most widely used therapeutic proteins used yearly by millions of people, especially for cosmetic purposes. Currently, its clinical use in certain types of pain is increasing, and its long-term duration of effects represents a special clinical value. Efficacy of BoNT/A in different types of pain has been found in numerous clinical trials and case reports, as well as in animal pain models. However, sites and mechanisms of BoNT/A actions involved in nociception are a matter of controversy. In analogy with well known neuroparalytic effects in peripheral cholinergic synapses, presently dominant opinion is that BoNT/A exerts pain reduction by inhibiting peripheral neurotransmitter/inflammatory mediator release from sensory nerves. On the other hand, growing number of behavioral and immunohistochemical studies demonstrated the requirement of axonal transport for BoNT/A's antinociceptive action. In addition, toxin's enzymatic activity in central sensory regions was clearly identified after its peripheral application. Apart from general pharmacology, this review summarizes the clinical and experimental evidence for BoNT/A antinociceptive activity and compares the data in favor of peripheral vs. central site and mechanism of action. Based on literature review and published results from our laboratory we propose that the hypothesis of peripheral site of BoNT/A action is not sufficient to explain the experimental data collected up to now.

An update on the neurologic applications of botulinum toxins

Initially used to treat strabismus in the 1970s, botulinum toxin now has more than a hundred possible medical applications. Its utility in neurologic conditions has largely involved treating movement disorders (particularly dystonia and conditions with muscle hyperactivity), although practically any hyperkinetic movement disorder may be relieved by botulinum toxin, including hemifacial spasm, tremor, tics, myoclonus, and spasticity. Although initially thought to inhibit acetylcholine release only at the neuromuscular junction, botulinum toxins are now recognized to inhibit acetylcholine release at autonomic cholinergic nerve terminals, as well as peripheral release of neurotransmitters involved in pain regulation. Thus, their use in neurology has been expanded to include headache and other pain syndromes, as well as hypersecretory disorders. This article highlights some of the common neurologic conditions currently improved by botulinum toxins and reviews the scientific evidence from research studies and clinical experience with these conditions.